(a) (i) Describe the approach to laboratory diagnosis of chronic myeloid leukemia – chronic phase. 10 marks (ii) Describe the…

Laboratory Diagnosis of Chronic Myeloid Leukemia (Chronic Phase)

Peripheral blood smear examination reveals marked leukocytosis (typically >100,000/μL) with a complete spectrum of myeloid precursors demonstrating a "left shift" (myelocytes, metamyelocytes, band forms), accompanied by prominent basophilia and eosinophilia. The Leukocyte Alkaline Phosphatase (LAP/NAP) score is characteristically low to absent, differentiating it from a leukemoid reaction. Bone marrow aspirate and biopsy show marked hypercellularity with granulocytic hyperplasia (elevated M:E ratio), dwarf megakaryocytes, and sea-blue histiocytes. Definitive cytogenetic and molecular confirmation relies on identifying the Philadelphia chromosome t(9;22)(q34;q11) via conventional karyotyping or Fluorescent In Situ Hybridization (FISH), and detecting the BCR-ABL1 fusion transcript using quantitative Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR).

Evolution of Myocardial Infarction and Cardiac Biomarkers

Gross and microscopic evolution over two weeks follows a defined timeline:

• 0 to 24 Hours: Grossly, dark mottling appears after 12 hours. Light microscopy demonstrates early coagulative necrosis, wavy myocardial fibers, hypereosinophilia, and marginal contraction band necrosis.
• 1 to 3 Days: Grossly exhibits a central yellow-tan softening with a hyperemic border. Microscopy shows total loss of nuclei and striations, with dense neutrophilic infiltration.
• 3 to 7 Days: Grossly, marked central softening with depressed hyperemic margins is visible. Microscopy demonstrates disintegration of dead myofibers and early phagocytosis by abundant macrophages.
• 7 to 14 Days: Grossly, the infarct border appears depressed and gelatinous red-purple. Microscopy reveals prominent vascularized granulation tissue with active fibroblastic proliferation and early collagen deposition.

Serum cardiac biomarkers confirm the diagnosis:

• Cardiac Troponins (cTnI and cTnT): Highly cardiospecific; levels rise within 2–4 hours, peak at 24–48 hours, and persist for 7–14 days.
• Creatine Kinase-MB (CK-MB): Rises within 4–6 hours, peaks at 18–24 hours, and normalizes within 48–72 hours, making it the diagnostic marker of choice for detecting early re-infarction.

Pharmacology Considerations

Beta-Blockers in Diabetics on OHAs: Non-selective beta-blockers impair counter-regulatory glycogenolysis and gluconeogenesis by blocking hepatic beta-2 receptors, thereby worsening hypoglycemia and delaying recovery. Concurrently, blockade of peripheral beta-1 receptors masks sympathoadrenal warning signs such as tachycardia, palpitations, and tremors, leaving diaphoresis (sympathetic cholinergic) as the sole, often overlooked indicator of life-threatening hypoglycemia.

Folic Acid with Methotrexate: Methotrexate competitively inhibits dihydrofolate reductase (DHFR), halting tetrahydrofolate generation. Supplementation with folic acid (or folinic acid/leucovorin rescue in high-dose chemotherapy) restores intracellular folate pools in normal tissues, preventing dose-limiting toxicities such as stomatitis, mucosal ulcerations, hepatotoxicity, and myelosuppression, while preserving the therapeutic response.

Varicella Infection and Post-Exposure Prophylaxis

The patient has Varicella (chickenpox). Transmission occurs via airborne respiratory droplets or direct contact with infectious vesicular fluid.

Pathogenesis and Course: Inhalation/Contact → Primary replication in upper respiratory tract mucosa and local lymphoid tissue → Primary viremia (days 4–6) with reticuloendothelial dissemination → Secondary viremia (days 10–14) → Fever and prodrome → Centripetal vesicular eruption in successive crops ("dewdrops on a rose petal") → Pustulation, umbilication, and crusting/scabbing.

Laboratory Diagnosis:

1. Tzanck smear demonstrating multinucleated giant cells and Cowdry A inclusion bodies.
2. Real-time PCR detecting Varicella Zoster Virus (VZV) DNA in vesicular scrapings.
3. Direct Fluorescent Antibody (DFA) staining of vesicular base exudates.

Post-Exposure Strategies:

1. Active Immunization: Live attenuated varicella vaccine administered within 3 to 5 days of exposure to susceptible, immunocompetent individuals.
2. Passive Immunization: Varicella-Zoster Immune Globulin (VZIG) administered intramuscularly within 96 hours (effective up to 10 days) for high-risk individuals, including immunocompromised patients, non-immune pregnant women, and neonates whose mothers contracted varicella peripartum.

Malarial Parasites in India and Smear Findings

The species prevalent in India are Plasmodium vivax (most common), Plasmodium falciparum, Plasmodium malariae, and the zoonotic Plasmodium knowlesi.

Plasmodium falciparum is notoriously responsible for life-threatening complications, including cerebral malaria, acute tubular necrosis ("blackwater fever"), non-cardiogenic pulmonary edema, severe lactic acidosis, and disseminated intravascular coagulation, mediated by cytoadherence and sequestration of parasitized RBCs via PfEMP-1.

Peripheral Blood Smear Characteristics:

• Plasmodium vivax: Parasitizes enlarged, pale reticulocytes containing fine, eosinophilic stippling (Schüffner's dots), highly amoeboid trophozoites, and compact, spherical gametocytes.
• Plasmodium falciparum: Parasitizes normal-sized red blood cells; shows high parasitemia, delicate multiple ring forms per RBC, appliqué/accole forms, double chromatin dots, and diagnostic crescent/banana-shaped gametocytes; late schizonts are rarely seen in peripheral blood due to deep vascular sequestration.
• Plasmodium malariae: Parasitizes mature, normal-to-small RBCs, featuring characteristic ribbon or rectangular "band-form" trophozoites, coarse Ziemann’s dots, and symmetrical "daisy-head" rosette schizonts containing 6 to 12 merozoites.

A systematic approach combining microscopic morphology, targeted molecular assays, and pathophysiology-driven therapeutics is vital for accurate differential diagnosis and effective clinical intervention across these conditions.