PUO in a 17-Year-Old Female - Next Steps After Negative Tier-1 & Tier-2 Workup

Immediate Gaps to Fill First

Tier-3: Next Investigations (Now Indicated)

1. CECT Chest, Abdomen and Pelvis (HIGH PRIORITY)

• USG can miss deep lymphadenopathy, mediastinal nodes, early solid tumors, and retroperitoneal masses
• Rules out occult lymphoma (Hodgkin's is classic in adolescent females), solid tumors, occult abscess, hepatosplenic TB, and mesenteric adenitis
• Must be done before bone marrow or biopsy

2. Echocardiography (HIGH PRIORITY)

• Blood cultures were negative, but culture-negative endocarditis (Bartonella, Coxiella/Q-fever, HACEK organisms, fungi) is a real entity
• Also screens for atrial myxoma - a rare but important cause of PUO with normal inflammatory markers
• Also request Coxiella burnetti (Q-fever) serology and Bartonella serology if echo shows any vegetation

3. 18F-FDG PET/CT (TIER-3 GOLD STANDARD if CT is inconclusive)

• Has the highest diagnostic yield (50-60% positive findings) in classic PUO after negative initial workup
• Identifies occult infections, deep lymph node disease, granulomatous inflammation, and malignancy simultaneously
• The EANM 2024 consensus guidelines recommend FDG-PET/CT early in the PUO workup to guide targeted biopsy
• Recent Frontiers in Medicine 2024 cohort (n=284) confirmed strong diagnostic value particularly for infection/inflammation and lymphoma

4. Bone Marrow Aspirate + Biopsy (if CT/PET non-revealing)

• Detects: leukemia, lymphoma with marrow infiltration, hemophagocytic lymphohistiocytosis (HLH), disseminated TB, leishmaniasis, histoplasmosis
• Send for culture (AFB + fungal), histology, and flow cytometry

5. Repeat Detailed Physical Examination

• Check specifically for: evanescent salmon-colored rash (Still's disease), lymph nodes (especially epitrochlear, posterior cervical), splenomegaly, subtle joint swelling, oral ulcers (Behcet's), rashes of SLE/vasculitis, fundoscopy for uveitis

Differential Diagnoses to Actively Rule Out in a 17-Year-Old Female

Practical Step-by-Step Priority Order

1. Send immediately: EBV/CMV serology, HIV, serum ferritin, LDH, peripheral smear, IGRA, Bartonella/Coxiella serology, anti-dsDNA + C3/C4, rK39
2. Imaging: CECT chest/abdomen/pelvis + Echocardiography
3. If CT inconclusive: FDG-PET/CT
4. If PET/CT inconclusive or lymph node identified: Lymph node biopsy (do not empirically treat)
5. If all above negative: Bone marrow aspirate + biopsy
6. Do NOT start empirical steroids or antibiotics unless diagnosis is confirmed or there is high clinical suspicion with imminent deterioration - this can mask lymphoma and infectious causes

PUO + Iron Deficiency Anemia (Normal-Low Ferritin) in a 17-Year-Old Female - Next Steps

What the New Finding Tells You

• Normal ferritin in IDA = ferritin was not elevated by acute-phase response, suggesting the anemia is from true iron depletion, NOT anemia of chronic disease
• In a 17-year-old female, IDA has three main causes: menstrual blood loss, GI blood loss/malabsorption, or dietary deficiency
• The fever + IDA combination strongly points to a GI source - particularly inflammatory bowel disease (Crohn's), celiac disease, or intestinal tuberculosis / parasitic infection

Step 1: Critical Questions to Ask (History Gaps)

Step 2: Immediate Blood Tests to Add

Step 3: Imaging - CECT Abdomen and Pelvis (NOW INDICATED)

• USG abdomen was normal but cannot reliably detect bowel wall thickening, mesenteric fat stranding, skip lesions of Crohn's, or ileocecal TB
• CECT specifically evaluates: terminal ileum, ileocecal junction, mesenteric lymph nodes, bowel wall enhancement
• Request CT enterography (CTE) if bowel disease is suspected - this is more sensitive for small bowel Crohn's than standard CECT

Step 4: Endoscopy (HIGH PRIORITY - TIER 3)

A. Upper GI Endoscopy (OGD) with duodenal biopsy

• Confirms celiac disease (Marsh classification on biopsy - villus blunting, crypt hyperplasia, intraepithelial lymphocytes)
• Detects H. pylori gastritis, erosive esophagitis, peptic ulcer disease causing occult blood loss
• Per Harrison's: "Diagnosis [of celiac] in adults with positive antibody levels is confirmed by endoscopy with small-intestinal biopsy"

B. Ileocolonoscopy with terminal ileum intubation + biopsies

• Detects Crohn's disease (cobblestoning, skip lesions, aphthous ulcers, ileal involvement)
• Detects ulcerative colitis, intestinal TB (ileocecal area), CMV colitis
• Intestinal TB can look exactly like Crohn's on colonoscopy - send biopsies for AFB culture, PCR, and histology (caseating vs. non-caseating granulomas)

Step 5: Gynecological Evaluation (Parallel Track)

• Refer to gynecology for assessment of menstrual blood loss as a contributing cause of IDA
• Pelvic USG was normal (rules out structural causes like fibroids, ovarian cysts)
• Assess for anovulatory cycles - common in adolescent females - which can cause heavy dysfunctional uterine bleeding without structural abnormality
• If menorrhagia confirmed: assess for von Willebrand disease (coagulation screen, VWF antigen + activity) - an important and commonly missed cause of heavy periods + IDA in teenage girls

Revised Differential Diagnosis with IDA as a Clue

Practical Priority Order

TODAY:
1. Detailed menstrual history + gynecology referral
2. Send: TTG-IgA + total serum IgA, EBV/CMV serology, HIV, IGRA,
         Stool FOBT x3, stool OCP, stool H. pylori antigen,
         serum iron + TIBC + transferrin saturation, fecal calprotectin

NEXT 48-72 HOURS:
3. CECT abdomen/pelvis (or CT enterography if bowel disease suspected)
4. Echocardiography (still needed - culture-negative endocarditis)

AFTER IMAGING RESULTS:
5. OGD with duodenal biopsy (celiac) + H. pylori CLO test
6. Ileocolonoscopy with terminal ileum intubation + biopsies
   (Crohn's vs. intestinal TB - send AFB culture, PCR, histology)

IF ALL ABOVE NEGATIVE:
7. Bone marrow aspirate + biopsy
8. FDG-PET/CT

How to Read an IGRA Test

What IGRA Measures

1. QuantiFERON-TB Gold Plus (QFT-Plus) - ELISA-based, measures IFN-γ in IU/mL
2. T-SPOT.TB - ELISPOT-based, counts spot-forming cells (SFCs)

Platform 1: QuantiFERON-TB Gold Plus (QFT-Plus)

The Four Tubes

How to Calculate Values

• TB1 - Nil = TB1 response
• TB2 - Nil = TB2 response
• Mitogen - Nil = Mitogen response

Official QFT-Plus Interpretation Table

The "25% of Nil" Rule - Why It Exists

• Nil = 4.0 IU/mL (already high baseline)
• TB1 - Nil = 0.40 IU/mL (meets ≥0.35 cutoff)
• But 0.40 is only 10% of 4.0 → does NOT meet the 25% rule → NOT positive

Platform 2: T-SPOT.TB (ELISPOT)

Four Wells

T-SPOT Interpretation

What Each Result Means Clinically

✅ POSITIVE

• TB infection (latent or active) is likely
• Does NOT differentiate between latent TB infection (LTBI) and active TB disease
• Does NOT tell you when infection occurred (recent vs. old)
• Magnitude of the value (e.g., 5.0 vs. 0.5 IU/mL) does NOT correlate with disease stage, activity, or risk of progression
• False positives with: M. kansasii, M. marinum, M. szulgai, M. gordonae (NOT with BCG vaccination)

❌ NEGATIVE

• TB infection is not likely
• But a negative result does NOT exclude active TB, especially in:
  • Immunocompromised patients (HIV, on steroids, biologics)
  • Very early infection (window period: 8-12 weeks after exposure)
  • Miliary TB or severely immunosuppressed (reduced sensitivity)
• Goldman-Cecil states: "The sensitivity of these tests is reduced in immunocompromised persons, persons with sarcoidosis, after live virus vaccination, and in persons with active TB"

⚠️ INDETERMINATE

1. Nil >8.0 IU/mL - High background IFN-γ (patient has active inflammatory/autoimmune process, or non-specific stimulation of cells). Blood may have been incubated too long.
2. Mitogen - Nil <0.5 IU/mL - Cells failed to respond to the positive control = immunosuppression, poor sample handling, improper tube filling, delay in transport

Key Advantages Over TST (Mantoux)

Critical Points to Remember

1. IGRA cannot distinguish LTBI from active TB - a positive result needs clinical context, CXR, and symptoms evaluation
2. Do not repeat IGRA after treatment - it usually stays positive even after successful treatment for LTBI; this is expected and not a sign of failure
3. Low-positive values (0.35-1.0 IU/mL) are in a "gray zone" - serial testing in this range can fluctuate between positive and negative; always interpret with clinical risk
4. In high-risk patients (HIV, household contacts), if IGRA is negative but clinical suspicion is high, treat for LTBI anyway - both TST and IGRA can be false negative
5. Dual testing (IGRA + TST together) is recommended only in high-risk + high-progression-risk patients (e.g., household contact + HIV); if either is positive, treat

IGRA Report Interpretation - Ms. Jumana, 15F

Raw Values from the Report

Step-by-Step Interpretation

Step 1: Is the Nil valid?

• Nil = 0.69 IU/mL → ≤8.0 IU/mL ✅
• The background is acceptable. The test is valid.

Step 2: Apply the two-part positivity criteria to TB Ag - Nil (0.25):

• 0.25 < 0.35 → ❌ FAILS

• 25% of 0.69 = 0.17 IU/mL
• 0.25 > 0.17 → ✅ Would pass this part...
• But since Criterion A already fails (<0.35), this is moot.

✅ RESULT: NEGATIVE

M. tuberculosis infection is NOT likely

Important Clinical Caveats for This Patient

1. This is a "Gray Zone Negative"

• TB Ag - Nil = 0.25 is close to the 0.35 cutoff but below it
• The Nil (background) is relatively high at 0.69 (normal is usually <0.2-0.3)
• A high Nil can represent non-specific immune activation from an active inflammatory or infectious process - which is consistent with her ongoing fever

2. IGRA Does NOT Rule Out Active TB or Intestinal TB

• IGRA is designed to detect latent TB infection (LTBI)
• In active TB (especially extrapulmonary/intestinal TB), IGRA sensitivity drops to 60-80%
• The test cannot exclude intestinal TB, which remains in her differential
• Per Goldman-Cecil: "The sensitivity of these tests is reduced in... persons with active TB"

3. No Mitogen Control Reported

• This lab did not include a mitogen tube (positive control for immune function)
• Without the mitogen result, we cannot confirm that her immune cells were functioning properly
• The lab note acknowledges this: "Where a poor response due to an immunosuppressive condition is suspected, a Mitogen control may be used"
• This is a significant limitation of this particular report

4. Window Period

• If she was exposed to TB within the last 8-12 weeks, IGRA can be falsely negative (pre-seroconversion window period)

What to Do Clinically

PUO - 17F - Updated Workup After Negative IGRA + Negative Stool Calprotectin

What the New Negatives Tell You

What Is Still NOT Ruled Out

🔴 Critical Missing Tests (Should Have Been Done Already)

Tier-3 Investigations Now Indicated

1. CECT Chest + Abdomen + Pelvis (TOP PRIORITY)

• Detects mediastinal and hilar lymphadenopathy (missed on plain CXR) - Hodgkin's lymphoma, sarcoidosis
• Detects retroperitoneal adenopathy - lymphoma
• Identifies occult solid tumors, splenic lesions, hepatic lesions
• Diagnoses intestinal TB (ileocecal thickening, mesenteric nodes) even with negative IGRA and normal CXR
• Per Frameworks for Internal Medicine: "The posterior cervical, epitrochlear, supraclavicular, hilar, mediastinal, and retroperitoneal lymph nodes are most likely to provide a diagnosis in patients with FUO"

2. Echocardiography

• Rules out culture-negative endocarditis (Bartonella, Coxiella, HACEK organisms, fungi)
• Rules out atrial myxoma - causes constitutional symptoms, fever, emboli - often missed as it can be normal on USG
• Blood cultures were negative but this does not exclude culture-negative endocarditis

3. Detailed Repeat Clinical Examination (Every Day)

• Salmon-pink evanescent rash appearing during fever - pathognomonic of AOSD (Systemic JIA)
• Per Frameworks: "AOSD is associated with bimodal age distribution with peaks between ages 15-25 years... The rash often appears when the patient is febrile and disappears during afebrile periods... Markedly elevated serum ferritin levels often >2000 ng/mL are characteristic"
• Lymphadenopathy (epitrochlear nodes especially - cat scratch disease, lymphoma)
• Pharyngitis (AOSD, EBV)
• Joint swelling/tenderness (AOSD)
• Any skin lesion, oral ulcer, perianal lesion

Revised Priority Differential Diagnosis

Practical Step-by-Step Plan RIGHT NOW

SEND TODAY (Blood Tests):
✅ EBV VCA IgM + IgG + EBNA IgG
✅ CMV IgM + IgG (or CMV PCR)
✅ HIV ELISA + p24 antigen
✅ SERUM FERRITIN (critical - if >2000 = AOSD)
✅ Anti-dsDNA + C3 + C4
✅ Serum ACE
✅ Bartonella henselae IgM + IgG
✅ Brucella agglutination test (Rose Bengal + Standard Agglutination Test)
✅ Serum LDH + uric acid (if not done)

IMAGING (Within 48 Hours):
✅ CECT chest + abdomen + pelvis (with IV contrast)
✅ Echocardiography (transthoracic)

CLINICAL:
✅ Observe patient during fever spikes for evanescent rash
✅ Document fever pattern - quotidian (once daily) or double-quotidian (twice daily) = AOSD
✅ Ask about cat contact (Bartonella), animal contact (Brucella, Q-fever)
✅ Thorough drug history - rule out drug fever

IF CT SHOWS LYMPHADENOPATHY:
✅ Lymph node excision biopsy
   (posterior cervical > epitrochlear > supraclavicular preferred over axillary/inguinal)

IF FERRITIN >2000 + QUOTIDIAN FEVER + RASH + PHARYNGITIS:
✅ Apply Yamaguchi criteria for AOSD diagnosis
✅ Refer rheumatology

IF ALL ABOVE NEGATIVE:
✅ 18F-FDG PET/CT (highest yield in unexplained PUO after 2nd tier workup)
✅ Bone marrow aspirate + biopsy

PUO + IDA (Low-Normal Ferritin) + Negative Calprotectin + Negative IGRA - What Now?

Synthesizing the Picture

1. GI malabsorption (celiac disease - most likely)
2. Occult GI blood loss (H. pylori gastritis, peptic ulcer, small bowel lesion)
3. Menstrual blood loss (heavy periods as IDA source, with a separate/coincidental fever cause)
4. Occult malignancy (lymphoma - even with normal LDH, early Hodgkin's possible)

NEXT STEP 1 (URGENT - Send Today): Blood + Stool Tests

For the IDA:

For the PUO (still missing):

NEXT STEP 2: Imaging - CECT Abdomen + Pelvis + Chest

• Deep retroperitoneal/mesenteric lymph nodes
• Mediastinal/hilar lymph nodes (Hodgkin's lymphoma, sarcoidosis)
• Bowel wall thickening (intestinal TB, early Crohn's - even with negative calprotectin)
• Hepatic/splenic micro-lesions

NEXT STEP 3: Echocardiography

NEXT STEP 4: Endoscopy (After Serology Results)

If TTG-IgA positive OR high clinical suspicion for celiac:

• OGD (Upper GI endoscopy) with 4-6 duodenal biopsies - Marsh classification (villus blunting, crypt hyperplasia, increased intraepithelial lymphocytes = Celiac)
• Also do CLO test for H. pylori during same scope

Even if TTG-IgA negative:

• OGD is still indicated in this case - a young female with PUO + IDA + fever where the GI source is not identified
• Ileocolonoscopy to assess terminal ileum (intestinal TB, Crohn's, even with negative calprotectin - early/patchy disease can give false-negative calprotectin)

Menstrual history first:

• Before ordering endoscopy, clarify menstrual blood loss - if heavy periods are the IDA source, the GI workup priority changes (though the fever still needs explaining)
• Ask specifically: clot passage, pad/tampon count per day, duration of heavy flow
• If menorrhagia confirmed: screen for von Willebrand disease (coagulation screen, VWF antigen + activity) - commonly missed in teenage girls with heavy periods

Revised Differential (After All Negatives So Far)

Summary Action Plan

IMMEDIATE (TODAY):
1. TTG-IgA + total serum IgA          ← most important single test
2. Serum iron + TIBC + transferrin saturation
3. EBV VCA IgM/IgG + CMV IgM/IgG
4. HIV ELISA
5. Stool H. pylori antigen + stool OCP (ova, cysts, parasites)
6. Stool FOBT x3
7. Anti-dsDNA + C3 + C4
8. Serum ACE + LDH + uric acid
9. Brucella agglutination

WITHIN 48-72 HOURS:
10. CECT chest + abdomen + pelvis (with IV contrast)
11. Echocardiography
12. Gynecology referral - menstrual history + VWF screen if menorrhagia

AFTER RESULTS:
- If TTG-IgA positive → OGD with duodenal biopsy
- If CT shows lymphadenopathy → lymph node biopsy
    (prefer posterior cervical / supraclavicular / epitrochlear)
- If CT normal + all serology negative → Ileocolonoscopy + OGD
- If all above negative → FDG-PET/CT + bone marrow biopsy

PUO - 17F - Tier-1 + Tier-2 Fully Negative - Structured Next Steps

Where We Stand: Mapping the Completed Workup

✅ Done and Negative (What Has Been Ruled Out)

🔴 NOT Yet Done - Critical Gaps

THE NEXT STEPS - Organized by Priority

PRIORITY 1: Blood Tests to Send TODAY

Group A - Viral Serology (Most Likely Diagnosis in This Age Group)

Group B - Autoimmune (Incomplete Screen So Far)

Group C - Infection (Missed/Uncommon)

PRIORITY 2: Imaging - WITHIN 48 HOURS

CECT Chest + Abdomen + Pelvis (with IV contrast) - NON-NEGOTIABLE

• Plain CXR misses: mediastinal adenopathy (Hodgkin's lymphoma), hilar adenopathy (sarcoidosis), subtle pulmonary nodules (miliary TB, histoplasmosis)
• USG misses: retroperitoneal nodes, deep mesenteric adenopathy, bowel wall thickening (intestinal TB even with negative IGRA), splenic micro-lesions, hepatic focal lesions

Echocardiography (Transthoracic)

• Rules out culture-negative endocarditis - Bartonella, Coxiella/Q-fever, HACEK organisms, fungi - ALL blood culture negative
• Rules out atrial myxoma - a rare but classic cause of PUO that mimics infection and connective tissue disease; USG abdomen will NOT detect this
• Per Merck Manual FUO guidelines: echocardiography is a standard Tier-3 investigation in all unexplained PUO

PRIORITY 3: Clinical Re-examination (Every Encounter)

PRIORITY 4: If CT Shows Lymphadenopathy - Lymph Node Biopsy

• Prefer excisional biopsy over needle aspiration (higher diagnostic yield)
• Send for: Histology (Reed-Sternberg cells for Hodgkin's), Flow cytometry (lymphoma panel), AFB culture + TB PCR (TB), Fungal culture (histoplasmosis, cryptococcus)

PRIORITY 5: If ALL of the Above Is Negative

Complete Diagnostic Checklist - Prioritized

TODAY - BLOOD:
□ EBV VCA IgM + IgG + EBNA IgG
□ CMV IgM + IgG
□ HIV ELISA + p24 antigen
□ Parvovirus B19 IgM
□ SERUM FERRITIN (most important single rheumatology test)
□ Anti-dsDNA + C3 + C4
□ Anti-CCP antibody
□ Brucella agglutination (SAT + Rose Bengal)
□ Bartonella henselae IgM + IgG
□ Q-fever (Coxiella) Phase I + II IgG/IgM
□ Serum ACE
□ Toxoplasma IgM + IgG
□ Peripheral blood smear (atypical lymphocytes, blasts)

WITHIN 48 HOURS - IMAGING:
□ CECT chest + abdomen + pelvis (IV contrast)
□ Echocardiography (transthoracic)

AFTER CT RESULTS:
□ Lymph node excisional biopsy (if adenopathy found)
□ Upper GI endoscopy + ileocolonoscopy (if bowel lesion found)

IF ALL NEGATIVE:
□ 18F-FDG PET/CT
□ Bone marrow aspirate + trephine biopsy

DO NOT:
✗ Start empirical steroids before excluding lymphoma
✗ Start empirical anti-TB before tissue diagnosis
✗ Start empirical antibiotics without a microbiological target

PUO + IDA + Normal Ferritin + Brucella Negative - What Now?

Synthesizing What the Combination Tells You

1. Malabsorption (celiac disease - iron absorbed in the duodenum/proximal jejunum)
2. Chronic GI blood loss (H. pylori gastritis, intestinal parasites, occult bleeding)
3. Menstrual blood loss (heavy dysfunctional uterine bleeding in adolescence)

THE NEXT STEPS - In Order of Priority

🔴 STEP 1: These Blood Tests Must Be Sent TODAY

A. For the IDA (GI/Malabsorption Workup)

B. For the PUO (Still-Untested Causes)

🔴 STEP 2: Gynecology Referral + Menstrual Assessment

• Heavy periods with clot passage, pad/tampon count >5/day, duration >7 days?
• If menorrhagia confirmed: this explains the IDA, but the fever still needs a separate explanation
• Screen for von Willebrand disease (coagulation screen + VWF antigen + VWF activity) - the most common inherited bleeding disorder in teenage girls; frequently undiagnosed
• If menstrual loss is the IDA cause AND fever remains unexplained → continue PUO workup separately

🟡 STEP 3: Imaging - Within 48-72 Hours

CECT Chest + Abdomen + Pelvis (with IV contrast)

• USG cannot detect mediastinal/hilar adenopathy (Hodgkin's lymphoma, sarcoidosis)
• USG cannot detect bowel wall thickening reliably (intestinal TB despite negative IGRA, early Crohn's despite negative calprotectin)
• USG cannot detect retroperitoneal adenopathy, mesenteric nodes, or early splenic infiltration
• Request CT enterography (CTE) specifically if small bowel disease suspected

Echocardiography

• Culture-negative endocarditis (Bartonella, Q-fever, HACEK) - all blood culture negative
• Atrial myxoma - classic cause of PUO mimicking infection

🟡 STEP 4: Endoscopy (After Serology Results)

OGD (Upper GI Endoscopy) + Duodenal Biopsy

• TTG-IgA positive → confirm celiac (Marsh classification on biopsy: villus blunting + crypt hyperplasia + increased intraepithelial lymphocytes)
• OR clinical suspicion remains high despite negative serology (IgA-deficient patients can have false-negative TTG-IgA → check total IgA first)
• Also perform CLO test / rapid urease test for H. pylori during same scope

Ileocolonoscopy with Terminal Ileum Intubation

• CT shows ileocecal abnormality
• FOBT positive
• Biopsy: send for histology + AFB culture + TB PCR (intestinal TB vs Crohn's)

🟢 STEP 5: If All Above Negative

Concise Priority Action List

TODAY:
1. Anti-TTG IgA + total serum IgA ← single most impactful test
2. EBV VCA IgM/IgG + EBNA IgG    ← most common missed fever cause
3. CMV IgM/IgG + HIV ELISA
4. Stool H. pylori antigen + stool OCP + FOBT x3
5. Serum iron + TIBC + transferrin saturation
6. Anti-dsDNA + C3/C4 + serum ACE
7. Toxoplasma IgM/IgG + Bartonella IgM/IgG
8. rK39 for visceral leishmaniasis (if Bihar/UP origin)

WITHIN 48 HOURS:
9. Gynecology referral - menstrual history + VWF screen if menorrhagia
10. CECT chest + abdomen + pelvis
11. Echocardiography

AFTER RESULTS:
12. OGD + duodenal biopsy if TTG-IgA positive or IgA-deficient
13. Ileocolonoscopy if CT/FOBT positive
14. Lymph node biopsy if CT shows adenopathy

IF STILL NEGATIVE:
15. FDG-PET/CT
16. Bone marrow aspirate + biopsy

• Anti-TTG IgA - for the IDA (celiac disease presenting as isolated IDA without diarrhea)
• EBV serology - for the fever (most common missed cause in a 17-year-old female, not yet tested)

Aldosterone / Renin Ratio - Fathima Neda, 12F

Raw Values

Result: ✅ NORMAL

ARR = 1.786 (Reference: <20.6)

What This Means Clinically

Primary Aldosteronism (PA) is EXCLUDED

• High aldosterone (autonomous overproduction from adrenal adenoma or bilateral hyperplasia)
• Low/suppressed renin (because the adrenal is producing aldosterone independently, bypassing the RAAS feedback)
• High ARR (>20.6, and particularly >45 = markedly elevated)

• Aldosterone is normal
• Renin is normal (not suppressed)
• ARR is very low at 1.786 - far below the cutoff
• This pattern rules out primary aldosteronism with confidence

Important Pre-Analytical Considerations

Clinical Context - Why Was This Test Ordered?

Next Steps Based on This Result

1. Renal Doppler ultrasound - renovascular hypertension (renal artery stenosis) is the most common cause of secondary HTN in children; renin is normal-high (46.08 at upper limit), which is compatible
2. 24-hour urine catecholamines + metanephrines - rule out pheochromocytoma
3. 24-hour urinary free cortisol + ACTH - rule out Cushing's syndrome
4. Renal function + urinalysis + urine protein:creatinine ratio - renal parenchymal disease (glomerulonephritis, reflux nephropathy)
5. Echocardiography - rule out coarctation of aorta, assess for end-organ damage (LVH)
6. Thyroid function (TSH) - hypothyroidism causes diastolic HTN

Combined Interpretation: Low Cortisol + Low ACTH + Normal ARR (Low-Normal Aldosterone + Normal Renin) in a 12-Year-Old Female

The Hormone Pattern at a Glance

Diagnosis: SECONDARY ADRENAL INSUFFICIENCY

The Logic - Step by Step

• Hypothalamus releases CRH → stimulates pituitary to release ACTH → ACTH stimulates adrenal cortex to produce cortisol
• If cortisol is low AND ACTH is also low, the pituitary is failing to drive the adrenal → this is secondary (pituitary) or tertiary (hypothalamic) insufficiency
• If this were primary adrenal insufficiency (Addison's disease), cortisol would be low BUT ACTH would be HIGH (pituitary screaming at a failing adrenal gland)

"Unlike primary adrenal insufficiency, the adrenal gland is not destroyed in secondary adrenal insufficiency. Since aldosterone secretion is primarily under control of the renin-angiotensin system, it remains unaffected."

• In primary adrenal insufficiency (Addison's): The entire adrenal cortex is destroyed → BOTH cortisol AND aldosterone are low → renin is HIGH (compensating for low aldosterone)
• In secondary adrenal insufficiency: Only the ACTH-dependent zona fasciculata (cortisol) is affected → aldosterone (zona glomerulosa, RAAS-dependent) is PRESERVED → aldosterone is normal, renin is normal

Comparison Table: Primary vs Secondary Adrenal Insufficiency

In a 12-Year-Old Girl - What Causes Secondary Adrenal Insufficiency?

Most Important Causes in a Child:

Clinical Features to Look for in This Child

What to Do Next - Urgent Investigations

URGENT:
1. MRI pituitary gland with gadolinium contrast
   (rule out craniopharyngioma, pituitary tumor, hypophysitis, LCH)

2. Full pituitary hormone panel:
   - GH + IGF-1 (growth hormone deficiency)
   - LH + FSH (gonadotropin deficiency)
   - TSH + Free T4 (central hypothyroidism)
   - Prolactin (elevated in stalk compression, low in hypopituitarism)
   - ADH/urine osmolality (diabetes insipidus)
   - Morning testosterone/estradiol (sex hormone axis)

3. Synacthen (ACTH stimulation) test:
   - Give 250 mcg cosyntropin IV
   - Measure cortisol at 0, 30, 60 minutes
   - Cortisol <18 mcg/dL (immunoassay) or <14 mcg/dL (mass spectrometry)
     at 60 min confirms adrenal insufficiency
   - In secondary AI, adrenal glands may still respond acutely to exogenous
     ACTH (as they are not destroyed), so a low-dose (1 mcg) test is preferred

4. Visual field testing (perimetry)
   - Bitemporal hemianopia = optic chiasm compression by craniopharyngioma

5. Ophthalmology referral
   - Papilloedema (raised ICP), optic atrophy

Immediate Management

• Hydrocortisone (glucocorticoid) replacement - weight-based dosing (~8-12 mg/m²/day)
• No mineralocorticoid (fludrocortisone) needed - aldosterone is normal (this is the key clinical difference from primary AI)
• Stress dosing education (3x normal dose during illness/surgery/"sick day rules")
• Medical alert bracelet
• Endocrinology referral urgently

Summary

MRI Pituitary with Gadolinium - What It Means

What Is an MRI?

What Is Gadolinium?

"Gadolinium remains excluded from the brain by the blood-brain barrier, except in areas where this barrier breaks down, such as inflammation or tumor. On T1 images, gadolinium-enhanced structures appear white."

• Healthy brain tissue has an intact blood-brain barrier → gadolinium cannot enter → stays dark
• Tumors, inflammation, abnormal blood vessels → barrier is disrupted → gadolinium leaks in → appears bright white on T1 images

Why Is the Pituitary Special?

What the Scan Looks Like - Standard Protocol

What It Is Looking For in This Patient (Fathima Neda, 12F)

Normal pituitary region → suggests functional cause
(exogenous steroids, autoimmune, idiopathic)

↓ If abnormal:

Tumor/mass lesion
├── Craniopharyngioma → Cystic + calcified suprasellar mass
│   (most common pituitary region tumor in children)
│   Usually mixed: cyst (bright T2) + calcification (dark T2/bright CT)
│   + solid enhancing portion
│
├── Pituitary adenoma → Small dark spot in bright gland
│   (less common in children)
│
└── Germinoma → Enhancing stalk/suprasellar mass in children
    (also causes diabetes insipidus)

Inflammation/infiltration
├── Lymphocytic hypophysitis → Enlarged, uniformly enhancing pituitary
│   + thickened stalk
│
├── Langerhans Cell Histiocytosis → Thickened pituitary stalk
│   Loss of posterior pituitary bright spot (diabetes insipidus)
│
└── Sarcoidosis → Stalk thickening + leptomeningeal enhancement

Structural
├── Empty sella → Pituitary flattened, sella filled with CSF
└── Septo-optic dysplasia → Small optic nerves + absent septum pellucidum

What the Report Will Say

1. Size of pituitary gland - normal height is <8 mm in children
2. Signal intensity on T1 and T2 - any bright or dark spots
3. Enhancement pattern - uniform vs. focal defect
4. Pituitary stalk - midline? thickened? deviated?
5. Optic chiasm - compressed? normal?
6. Suprasellar region - any mass above the sella
7. Posterior pituitary bright spot - normally bright on T1 (stores ADH); absent in central diabetes insipidus

Practical Instructions for the Patient/Family

• No ferromagnetic metal implants (pacemakers, certain aneurysm clips) - inform radiologist
• Gadolinium injection into a vein (antecubital) - small sting, generally safe
• Scan duration: ~30-45 minutes
• Patient must lie still in the scanner - children may need sedation if unable to cooperate
• Loud knocking noise is normal - ear protection provided
• Gadolinium is safe in normal kidney function; if RFT is abnormal, inform radiologist

• Drink plenty of water to flush gadolinium through kidneys
• Results usually available within 24-48 hours

Lab Report Interpretation - Jumana, 15F (17 July 2026)

All Values at a Glance

Test-by-Test Interpretation

1. EBV VCA IgG = 8.44 (STRONGLY POSITIVE) + EBV VCA IgM = 0.37 (NEGATIVE)

Note: EBNA IgG was not tested - adding it would help confirm this is truly past (not early acute) infection. In primary acute EBV, EBNA IgG is absent early, while in past infection it is positive.

2. CMV IgG = 5.96 (POSITIVE) + CMV IgM = 1.02 (NEGATIVE)

• CMV IgM negative (1.02, cutoff >4.2) → No acute/active CMV infection
• CMV IgG positive (5.96, cutoff >2.0) → Past CMV exposure, latent infection (very common in the general population)

3. ⚠️ Cortisol 8AM = 9.75 µg/dL (LOW-NORMAL / BORDERLINE)

"Both healthy individuals and patients with adrenal insufficiency may have indeterminate results (3 to 18 µg/dL) that require additional evaluation."

4. HIV 1&2 ELISA = 0.08 OD (NON-REACTIVE)

• Result: 0.08 OD
• Cutoff: Non-reactive <0.25, Reactive >0.25
• HIV is conclusively excluded. The result (0.08) is far below the reactive threshold.

Integrated Clinical Summary

What This Means for the PUO Workup

Immediate Next Steps:

URGENT:
1. Synacthen (ACTH stimulation) test
   - Give 250 mcg cosyntropin IV
   - Measure cortisol at 0, 30, 60 minutes
   - Peak <18 µg/dL = adrenal insufficiency confirmed

2. Serum ACTH (9AM, fasting) - if not already done
   - If ACTH is LOW with low cortisol = secondary adrenal insufficiency
     → MRI pituitary with gadolinium urgently
   - If ACTH is HIGH with low cortisol = primary adrenal insufficiency
     → Adrenal imaging (CT adrenals)

3. CECT chest + abdomen + pelvis (still pending)
   - Lymphoma, sarcoidosis, intestinal TB remain in differential

4. Echocardiography (still pending)
   - Culture-negative endocarditis, atrial myxoma

5. Anti-TTG IgA + stool OCP still recommended
   (celiac disease, parasites as IDA cause)

PUO - 17F - Extensive Negative Workup + IDA - Where We Are Now

Master Checklist: What Has Been Done and Excluded

What Has NOT Been Done - Critical Remaining Gaps

THE NEXT STEPS

🔴 PRIORITY 1: Tests to Send Immediately (Today)

A. For the IDA - This Is Now the Primary Diagnostic Lead

B. For the PUO - Still Missing Tests

🔴 PRIORITY 2: Imaging - Within 48-72 Hours (Cannot Be Delayed Further)

CECT Chest + Abdomen + Pelvis (with IV contrast)

Echocardiography

• Culture-negative endocarditis (Bartonella, Q-fever, HACEK, fungi) - all blood culture negative
• Atrial myxoma - rare but classic cause of PUO in young women; causes fever + embolic events; USG abdomen is negative

🟡 PRIORITY 3: Endoscopy (After Serology and Imaging)

OGD (Upper GI Endoscopy) with Duodenal Biopsies - HIGH PRIORITY

• IDA with suspected malabsorption as the mechanism
• Essential regardless of TTG-IgA result (IgA deficiency can give false-negative TTG)
• Per Harrison's: diagnosis of celiac requires duodenal biopsy confirming villus blunting + crypt hyperplasia + intraepithelial lymphocytes (Marsh classification)
• Also perform CLO test / rapid urease test for H. pylori during same scope
• 2024 PubMed data confirms: "diagnostic yield of EGD is significantly higher than colonoscopy in younger IDA patients"

Ileocolonoscopy with Terminal Ileum Biopsy

• If CT shows ileocecal abnormality, or FOBT positive, or stool OCP shows eggs
• Terminal ileum biopsy for intestinal TB (caseating granulomas, AFB culture) vs Crohn's (non-caseating)

🟡 PRIORITY 4: Gynaecology Referral

• Heavy periods (menorrhagia): clot passage, >5 pads/day, >7 days duration?
• If menorrhagia is confirmed, this explains the IDA - but the fever still needs a separate explanation
• Screen for von Willebrand disease (coagulation screen + VWF antigen + VWF ristocetin cofactor activity) - most common inherited bleeding disorder in teenage girls; routinely missed

🟢 PRIORITY 5: If All Above Is Negative

The Full Action Plan

TODAY - BLOOD:
□ Anti-TTG IgA + total serum IgA          ← #1 priority
□ Stool H. pylori antigen
□ Stool OCP x3 (concentration technique)
□ Stool FOBT x3
□ Serum iron + TIBC + transferrin saturation
□ HbA2 + HbF (HPLC) if thalassaemia possible
□ Serum ACE
□ Anti-dsDNA + C3 + C4
□ Toxoplasma IgM/IgG
□ Bartonella henselae IgM/IgG
□ Q-fever (Coxiella) serology
□ Morning cortisol 8AM + ACTH (simultaneously)
□ Parvovirus B19 IgM
□ rK39 (if from endemic area)

GYNAECOLOGY:
□ Detailed menstrual history
□ Coagulation screen + VWF antigen/activity
   (if menorrhagia confirmed)

WITHIN 48-72 HOURS:
□ CECT chest + abdomen + pelvis (IV contrast)
□ Echocardiography (transthoracic)

AFTER RESULTS:
□ OGD + duodenal biopsy x4-6 (if TTG-IgA positive OR 
  IgA deficient OR high clinical suspicion for celiac)
□ Ileocolonoscopy + TI biopsy (if CT/FOBT positive)
□ Lymph node excision biopsy (if CT shows adenopathy)
  - Prefer posterior cervical / supraclavicular /
    epitrochlear over axillary / inguinal

IF ALL STILL NEGATIVE:
□ 18F-FDG PET/CT
□ Bone marrow aspirate + trephine biopsy
□ Consider drug fever (review ALL medications)
□ Consider factitious fever (supervised temperature measurement)

Ranked Remaining Differential Diagnosis