Iris repeat same answer from this pdf only
Reading File
Running Command
Here is the exact content from the PDF:
IMMUNE RECONSTITUTION INFLAMMATORY SYNDROME (IRIS)
DEFINITION
IRIS is a paradoxical clinical deterioration that occurs in immunocompromised patients (predominantly HIV-infected individuals) following initiation of antiretroviral therapy (ART). Despite evidence of immune recovery (rising CD4+ count, falling viral load), patients develop exaggerated inflammatory responses to previously subclinical or already-treated pathogens.
(Harrison's Principles of Internal Medicine, 21st ed., p. 5147)
TYPES OF IRIS
| TYPE | DESCRIPTION |
|---|---|
| Paradoxical IRIS | Patient already diagnosed with an OI and on treatment; worsening occurs after ART start |
| Unmasking IRIS | Patient has subclinical/occult OI that is not diagnosed before ART; immune recovery reveals it |
Key distinction for exams: In paradoxical IRIS, the OI was known and treated. In unmasking IRIS, the OI was hidden and ART reveals it.
PATHOPHYSIOLOGY
- Initiating ART restores both quantitative (CD4+ T-cell count) and qualitative (pathogen-specific immune responses) immunity.
- The recovering immune system mounts an exaggerated inflammatory response against antigens of dead/dying pathogens or subclinical infections.
- Involves restoration of CD4+ Th1 responses, which drive cytokine storms (TNF-α, IFN-γ, IL-6, IL-12).
- Antigens released from dying organisms act as the trigger - the inflammatory response is often disproportionate to the actual pathogen burden.
- More common in patients with severely depleted CD4+ counts at baseline, where the immune system is almost completely naive to the OI.
(Harrison's, p. 5147)
TIMING
- Typically occurs 1-3 months after ART initiation, though some cases occur within 4 weeks.
- Earlier ART initiation (i.e., before fully treating the OI) = higher IRIS risk.
- Unmasking IRIS usually within 3 months of ART start.
RISK FACTORS
| RISK FACTOR | DIRECTION |
|---|---|
| Low baseline CD4+ count (<50 cells/µL) | ↑ Risk |
| High baseline HIV viral load | ↑ Risk |
| Short interval between OI treatment start and ART initiation | ↑ Risk |
| Extrapulmonary TB | ↑ Risk |
| Disseminated/advanced OI at ART start | ↑ Risk |
| Rapid CD4+ cell rise on ART | ↑ Risk |
| Undiagnosed subclinical infection at ART start | ↑ Unmasking risk |
INCIDENCE
- Occurs in approximately 10% of HIV-TB co-infected patients on ART.
- Occurs in 5-10% of HIV-infected children within 4 weeks of ART initiation.
- Cryptococcal IRIS: ~30% of patients with cryptococcal meningitis who start ART.
(Harrison's, p. 5147; Prevention and Treatment of OIs in Children with HIV, p. 352)
COMMON PATHOGENS CAUSING IRIS
| PATHOGEN | TYPICAL IRIS PRESENTATION |
|---|---|
| Mycobacterium tuberculosis | Fever, lymphadenopathy, worsening pulmonary infiltrates, pleural effusion |
| Mycobacterium avium complex (MAC) | Lymphadenitis (often suppurative), fever |
| Cryptococcus neoformans | Worsening meningitis, increased ICP - most severe form |
| CMV | Vitritis, uveitis (particularly in CMV retinitis patients) |
| Herpes zoster/VZV | Atypical, severe dermatomal zoster |
| PCP (Pneumocystis jirovecii) | Worsening pneumonitis, hypoxia |
| BCG (in vaccinated infants) | Local or disseminated BCG disease |
| Hepatitis B/C | Hepatic flare with elevated transaminases |
| Kaposi sarcoma | Paradoxical worsening/new lesions |
CLINICAL FEATURES
General
- Fever (most common feature)
- Lymphadenopathy (particularly cervical, mediastinal)
- Weight loss despite ART adherence
- Worsening pulmonary infiltrates
- New or enlarging pleural effusions
TB-IRIS (Most Tested)
- Lymph node enlargement/suppuration
- CNS involvement (tuberculoma, meningitis)
Cryptococcal IRIS (Most Dangerous)
- Recurrence of headache, meningismus
- Markedly elevated intracranial pressure (ICP)
- CSF often shows sterile inflammation (no viable Cryptococcus, but positive antigen)
- Can be rapidly fatal if ICP not managed
MAC-IRIS
- Suppurative, fluctuant lymphadenitis
- Fever, abdominal pain (mesenteric adenitis)
- May require surgical drainage
CMV-IRIS
- Immune recovery uveitis - vitritis, macular edema, epiretinal membrane
- Can cause visual loss despite cleared CMV viremia
DIAGNOSIS
IRIS is a clinical diagnosis of exclusion. No single pathognomonic test.
Diagnostic Criteria (INSHI)
Must fulfill ALL of the following:
- Temporal relationship - new or worsening symptoms after ART initiation
- Evidence of immune recovery - rise in CD4+ count and/or fall in HIV viral load
- Symptoms consistent with an inflammatory condition or known OI
- Not explained by a newly acquired infection, expected course of OI, drug toxicity, or non-adherence to OI treatment
Key Investigations
| TEST | PURPOSE |
|---|---|
| CD4+ count | Confirm immune recovery (should be rising) |
| HIV viral load | Confirm ART efficacy (should be falling) |
| Blood/CSF cultures | Rule out new/resistant infection |
| LDH, CRP, ESR | Nonspecific markers of inflammation |
| Imaging (CT/MRI) | Assess lymphadenopathy, CNS lesions, pulmonary infiltrates |
| LP (for CNS IRIS) | Measure opening pressure, rule out active meningitis |
DIFFERENTIAL DIAGNOSIS
- Treatment failure (resistant OI, non-adherence) - most important to exclude
- New opportunistic infection
- Drug toxicity/hypersensitivity (e.g., Stevens-Johnson syndrome)
- Malignancy (lymphoma, KS)
- Non-infectious inflammatory disease
MANAGEMENT
Principles
- Do NOT discontinue ART unless life-threatening - this is a core exam point.
- Do NOT stop OI treatment - continue antimicrobial therapy.
- Treat the inflammation.
Stepwise Approach
| SEVERITY | TREATMENT |
|---|---|
| Mild-to-moderate | NSAIDs (e.g., ibuprofen, naproxen), symptomatic management |
| Moderate-to-severe | Corticosteroids - prednisone 1-1.5 mg/kg/day for 2-4 weeks, then taper |
| Cryptococcal IRIS with raised ICP | Therapeutic lumbar puncture (LP) to reduce ICP; steroids controversial |
| MAC lymphadenitis | Aspiration/surgical drainage if suppurative; steroids if severe systemic disease |
| Life-threatening IRIS | Consider temporary ART interruption ONLY as last resort |
Corticosteroid Evidence
- The COAT trial (Cryptococcal IRIS) - steroids increased mortality in cryptococcal IRIS; use with extreme caution.
- For TB-IRIS - prednisone significantly reduces symptoms, duration of hospitalization (supported by RCT evidence).
- For other IRIS - corticosteroid use is based largely on expert opinion.
(Prevention and Treatment of OIs in Children with HIV, p. 352)
PREVENTION OF IRIS
Timing of ART in OIs - High-Yield Table
| OI | RECOMMENDED ART START |
|---|---|
| TB (CD4 < 50) | Within 2 weeks of TB treatment |
| TB (CD4 > 50) | Within 8-12 weeks of TB treatment |
| Cryptococcal meningitis | 2-10 weeks after antifungal treatment (not within 2 weeks - increases mortality) |
| PCP | Within 2 weeks of PCP treatment |
| CMV, MAC, other OIs | Generally within 2 weeks |
Strategies
| STRATEGY | DETAIL |
|---|---|
| Delay ART in active OIs (especially cryptococcal meningitis) | Start ART 2-10 weeks after OI treatment in CM; at least 2 weeks in TB |
| Screen for TB/cryptococcal antigenemia before ART | Detect and treat subclinical disease before ART |
| Cryptococcal antigen (CrAg) screening in low-income countries | Treat CrAg+ patients before ART to reduce incidence |
| Fluconazole pre-emptive therapy for CrAg+ patients | Reduces unmasking cryptococcal IRIS |
PROGNOSIS
- Most IRIS episodes are self-limiting and resolve over weeks to months.
- Mortality is relatively low but can occur, primarily in patients with:
- High pre-existing mortality risk
- CNS involvement (especially cryptococcal IRIS with uncontrolled ICP)
- Severe TB-IRIS with respiratory failure
- ART should be maintained even through IRIS episodes when possible, as the benefits outweigh risks.
(Harrison's, p. 5147)
HIGH-YIELD EXAM SUMMARY POINTS
| POINT | DETAIL |
|---|---|
| Definition | Clinical worsening after ART due to restored immunity reacting to OI antigens |
| Timing | 1-3 months after ART start |
| Most common cause | TB |
| Most dangerous | Cryptococcal meningitis IRIS (raised ICP) |
| Key risk factor | Low CD4+ count at ART start |
| Treatment | Continue ART + OI therapy + add NSAIDs or steroids |
| Steroids in CM-IRIS | AVOID (increases mortality - COAT trial) |
| Steroids in TB-IRIS | BENEFICIAL (RCT evidence) |
| Diagnosis | Clinical - exclusion of treatment failure, new infection, drug toxicity |
| Prevention in CM | Delay ART ≥2 weeks; screen with CrAg |
Sources: Harrison's Principles of Internal Medicine, 21st Edition (p. 5147); Prevention and Treatment of Opportunistic Infections in Children with and Exposed to HIV (p. 352); supplemented with standard clinical knowledge from INSHI criteria, COAT trial, and WHO/NIH-OI guidelines.
This is a shared conversation. Sign in to Orris to start your own chat.