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Case Interpretation - 54y/M, Peripheral Blood + Bone Marrow

Transcription of Findings

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Interpretation

Key Observations Analyzed:

• Normal M:E = 2:1 to 4:1
• This extreme elevation (nearly 4x upper limit) reflects a massive myeloid expansion with relative erythroid suppression
• In CML, M:E is typically ≥10:1 with a classic "myelocyte bulge"
• In this case, myelocytes account for ~20% of BM cells with maturation proceeding to mature neutrophils - this is characteristic of reactive myeloid hyperplasia

• Toxic granulation = coarse dark azurophilic granules in neutrophils due to retained primary granules
• This is a REACTIVE feature - seen in severe infection, sepsis, burns, inflammatory states
• In true CML, toxic granulation is typically absent

• Nuclear budding and karyorrhexis in erythroid precursors
• The erythropoiesis is micronormoblastic, suggesting underlying iron deficiency or chronic disease limiting effective erythropoiesis
• Only 6% erythroid cells in BM (severely reduced)

• Presence of both forms indicates active but reactive megakaryopoiesis
• In CML, megakaryocytes are classically small and hypolobated ("dwarf" megakaryocytes)
• Normal/mixed morphology favors reactive etiology

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Differential Diagnosis

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The Critical Distinguishing Test: BCR-ABL1 (Philadelphia chromosome)

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Diagnostic Approach

• BCR-ABL1 FISH / RT-PCR on peripheral blood - the single most important test
  • Positive = CML (chronic phase)
  • Negative = reactive/leukemoid reaction - look for cause

• Leukemoid reaction: LAP score elevated (>120)
• CML: LAP score low (0-15)
• Quick, inexpensive, though less definitive than BCR-ABL

• Infection workup: Blood cultures, CXR/CT chest (TB, fungal), urine cultures, serology
• Inflammatory markers: CRP, ESR, procalcitonin
• Malignancy screen: CT chest/abdomen/pelvis, tumor markers (CEA, CA-125, PSA)
• Bone marrow biopsy (trephine): For reticulin fibrosis, infiltration

• Serum ferritin, iron, TIBC (micronormoblastic picture suggests iron deficiency or ACD)
• Serum B12, folate (for any macrocytic contribution)
• Peripheral film for specific RBC morphology

• Cytogenetics (karyotype), blast count
• Stage (chronic/accelerated/blast phase)
• Tyrosine kinase inhibitor (imatinib first-line, or nilotinib/dasatinib)

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Summary Statement

1. A leukemoid reaction secondary to severe infection/inflammation/malignancy (favored by toxic granulation, mature neutrophil dominance, mixed megakaryocyte morphology), or
2. CML chronic phase (cannot be excluded by morphology alone)

• Harrison's Principles of Internal Medicine 22E - "Persistent neutrophilia with cell counts ≥30,000-50,000/µL is called a leukemoid reaction... In a leukemoid reaction, the circulating neutrophils are usually mature and not clonally derived."
• Goldman-Cecil Medicine - "From this smear, it would be impossible to distinguish a leukemoid reaction from CML. Distinction would depend on determination of the presence or absence of BCR-ABL fusion."
• Quick Compendium of Clinical Pathology 5th ed. - "In CML, the LAP score is typically low, between 0 and 15... Leukemoid reaction (reactive neutrophilia) is associated with an elevated LAP score."

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Approach to Erythrocytosis on Peripheral Smear (PS)

Definition

• Hb >16.5 g/dL in men / >16.0 g/dL in women
• Hct >49% in men / >48% in women
• Or red cell mass >25% above mean normal predicted value

"Unless the hemoglobin level is ≥20 g/dL (Hct ≥60%), it is not possible to distinguish true erythrocytosis from disorders causing plasma volume contraction."

• Harrison's Principles of Internal Medicine 22E

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Step 1 - The Primary Classification: Relative vs. Absolute

ERYTHROCYTOSIS ON PS
        │
        ▼
Is the RBC mass truly elevated?
        │
   ┌────┴────┐
   ▼         ▼
RELATIVE   ABSOLUTE

Relative (Spurious/Apparent) Erythrocytosis

• RBC mass is NORMAL - only plasma volume is reduced
• Also called Gaisböck's syndrome / stress erythrocytosis / pseudopolycythemia
• Causes:
  • Acute: dehydration (vomiting, diarrhea, burns, diuretics)
  • Chronic: hypertension, tobacco, ethanol abuse, obesity, androgens

Henry's Clinical Diagnosis - "Relative polycythemia refers to an increase in Hct or red cell count as a result of decreased plasma volume; total red cell mass is not increased."

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Step 2 - If Absolute Erythrocytosis: Primary vs. Secondary

ABSOLUTE ERYTHROCYTOSIS
          │
    ┌─────┴──────┐
    ▼             ▼
PRIMARY        SECONDARY
(EPO-           (EPO-
independent)    driven)
    │             │
   PV +      ┌───┴────┐
  congenital  ▼        ▼
            APPRO-   INAPPROP-
            PRIATE   RIATE
            (hypoxia) (ectopic)

A. Primary Erythrocytosis (EPO-independent)

B. Secondary Erythrocytosis - Appropriate (Hypoxia-driven, EPO elevated)

C. Secondary Erythrocytosis - Inappropriate (EPO ectopic/non-hypoxic)

D. Congenital/Familial (EPO pathway mutations)

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Step 3 - The Diagnostic Algorithm

Initial Assessment

1. Repeat CBC - confirm persistent elevation (exclude lab error)
2. Clinical history - smoking, altitude, drugs (androgens, EPO, SGLT2i), renal disease, family history
3. Examination - splenomegaly? aquagenic pruritus? plethora? erythromelalgia? thrombosis history?

Step 4 - Two Pivotal Tests (run simultaneously)

         ┌─────────────────────┐
         │  Serum EPO + JAK2   │
         │  V617F mutation     │
         └──────────┬──────────┘
                    │
        ┌───────────┼───────────┐
        ▼           ▼           ▼
    EPO low      EPO normal   EPO high
    JAK2 +ve     JAK2 -ve     JAK2 -ve
        │           │           │
        ▼           ▼           ▼
       PV      Check O2      Secondary
    (see WHO   Sat + check    cause
    criteria)   congenital    (hypoxia
                mutations    or ectopic)

"A normal serum erythropoietin level does not exclude the presence of PV, but an elevated erythropoietin level is most consistent with a secondary cause."

"Not everyone expressing a low JAK2 V617F quantitative mutation allele burden (VAF ≤5%) actually has a blood disease."

Arterial Blood Gas / Pulse Oximetry

• SaO2 <92% → hypoxic secondary erythrocytosis
• If SaO2 normal but EPO elevated → check for high-affinity Hb variants (P50), ectopic EPO sources

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Step 4 - WHO 2016 Diagnostic Criteria for PV (if suspected)

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Step 5 - Peripheral Smear Specific Findings

Harrison's 22E - "Only three situations cause microcytic erythrocytosis: β-thalassemia trait, hypoxic erythrocytosis, and PV. With β-thalassemia trait, RDW is usually normal; with hypoxic erythrocytosis or PV, RDW may be elevated due to associated iron deficiency."

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Step 6 - Further Workup Based on Pathway

If PV confirmed:

• BM biopsy (panmyelosis + pleomorphic megakaryocytes)
• Risk stratification (age >60 or prior thrombosis = high risk)
• Treatment: phlebotomy (target Hct <45%), low-dose aspirin, hydroxyurea (high risk)
• JAK2 inhibitor (ruxolitinib) for refractory/symptomatic disease

If secondary (hypoxic):

• PFTs, overnight oximetry (sleep study), echo (R→L shunt)
• Treat underlying cause; phlebotomy only for symptomatic hyperviscosity

If secondary (ectopic EPO):

• CT chest/abdomen/pelvis
• Renal Doppler (renal artery stenosis)
• Liver function + AFP (HCC)
• MRI head (cerebellar hemangioblastoma)

If congenital suspected (young patient, family history, JAK2-negative):

• P50 determination (high-affinity Hb)
• VHL sequencing, PHD2, EPAS1 mutations
• Genetic counseling

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Summary Flowchart

Elevated Hb/Hct on PS
         ↓
Is Hb ≥20 g/dL?
  No → Measure red cell mass + plasma volume
        (or use clinical + lab clues)
         ↓
Relative? → Treat cause (dehydration/drugs)
         ↓
Absolute confirmed
         ↓
Serum EPO + JAK2 V617F
         ↓
┌─────────────────────────────────────────┐
│ EPO low + JAK2+  → PV (confirm with WHO │
│                    criteria, BM if needed│
│ EPO high + JAK2- → Secondary erythrocytosis
│    → SaO2 check:
│        Low SaO2 → Hypoxic (COPD, OSA, altitude, CHD)
│        Normal SaO2 → Ectopic EPO (renal/hepatic tumor,
│                       high-affinity Hb, renal disease)
│                       or congenital (VHL, PHD2, EPAS1)
│ EPO normal + JAK2-→ Borderline/congenital/relative
│    → JAK2 exon 12, LNK mutation
│    → P50, VHL sequence
└─────────────────────────────────────────┘

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Causes of Neutrophilic Leukocytosis

Definition

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Mechanisms (Pathophysiologic Basis)

Robbins & Kumar Pathologic Basis of Disease - "In acute infection there is a rapid increase in the egress of mature granulocytes from the bone marrow pool, mediated through effects of TNF and IL-1. If infection is prolonged, IL-1, TNF, and inflammatory mediators stimulate macrophages and marrow stromal cells to produce increased hematopoietic growth factors."

Henry's Clinical Diagnosis - "An increase in immature peripheral blood granulocytes is termed a 'shift to the left.' Increased WBCs with left shift and toxic features may resemble leukemia - termed a 'leukemoid reaction.'"

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Causes - Organized by Category

1. INFECTIONS (Most Common Cause)

"Pyogenic bacteria especially induce neutrophilia. More virulent agents result in higher neutrophil counts; when the infection is overwhelming, toxic neutropenia with a shift to the left can occur, more commonly in the elderly." - Henry's Clinical Diagnosis

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2. INFLAMMATION / TISSUE NECROSIS

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3. DRUGS

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4. PHYSIOLOGIC / TRANSIENT CAUSES

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5. METABOLIC DISORDERS

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6. HEMATOLOGIC / MARROW STIMULATION

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7. MALIGNANCIES

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8. PRIMARY HEMATOLOGIC (NEOPLASTIC / CONGENITAL)

Acquired (Clonal)

Congenital/Hereditary

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Peripheral Smear Clues with Neutrophilia

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Quick Memory Aid - "INDIA MEN"

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