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

(a)(i) Laboratory diagnosis of chronic myeloid leukaemia (chronic phase)

A complete blood count typically shows anaemia, marked leukocytosis and often thrombocytosis. The 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, with a bimodal peak of myelocytes and segmented neutrophils and blasts under 10% (under 2% in most cases); chronic phase is defined by blasts below 10% in blood and marrow (the WHO 2022 classification has dropped accelerated phase in favour of risk features, with blast phase at ≥20% blasts or extramedullary blast proliferation). 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 (usually the p210 e13a2/e14a2 transcript) using quantitative Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR); demonstration of BCR::ABL1 is mandatory for diagnosis. Baseline quantitative PCR on the International Scale serves for monitoring response to tyrosine kinase inhibitors (major molecular response is BCR::ABL1 ≤0.1%), and risk scores (Sokal, ELTS) use spleen size, age, platelet count and blasts. Other supportive findings are raised serum uric acid, LDH and vitamin B12 (from increased transcobalamin).

(a)(ii) 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 and the preferred marker; levels rise within 2–4 hours (detectable within 1 hour with high-sensitivity assays), peak at 24–48 hours, and persist for 7–14 days. Under the Fourth Universal Definition of MI (2018), MI requires a rise and/or fall of troponin with at least one value above the 99th percentile upper reference limit plus clinical evidence of ischaemia (symptoms, new ECG changes, Q waves, imaging or angiographic thrombus). High-sensitivity troponin permits rapid 0/1-hour or 0/2-hour rule-in and rule-out algorithms (ESC).
• Creatine Kinase-MB (CK-MB): Rises within 4–6 hours, peaks at 18–24 hours, and normalizes within 48–72 hours, making it useful for detecting early re-infarction; myoglobin rises earliest but is non-specific and is now rarely used.

(b)(i) Beta-blockers in diabetics on oral hypoglycaemic agents

The caution applies mainly to non-selective beta-blockers (propranolol) in patients on insulin or insulin secretagogues (sulfonylureas, glinides) that can cause hypoglycaemia. 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 and beta-2 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 (hypoglycaemia unawareness). Unopposed α-adrenergic stimulation during hypoglycaemia can also cause a hypertensive surge with bradycardia. β-blockers may additionally worsen glycaemic control by reducing β2-mediated insulin release and increasing insulin resistance (older agents like atenolol and metoprolol more than carvedilol or nebivolol). Hence they are not absolutely contraindicated: cardioselective (β1) blockers or vasodilating β-blockers such as carvedilol and nebivolol can be used when clearly indicated (post-MI, heart failure), with patient education and glucose monitoring, while ACE inhibitors, ARBs or calcium-channel blockers are preferred for uncomplicated hypertension.

(b)(ii) 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. In low-dose weekly methotrexate for rheumatoid arthritis or psoriasis (7.5–25 mg once a week), folic acid 5 mg once weekly (on a different day) or 1 mg daily reduces gastrointestinal, hepatic and haematological toxicity and treatment discontinuation without reducing efficacy, because the anti-inflammatory effect relies mainly on adenosine release rather than folate depletion. In high-dose methotrexate for cancer, folic acid is ineffective because it must itself be reduced by the inhibited DHFR; instead folinic acid (leucovorin, already reduced) is given 24–36 hours later as rescue, bypassing the block in normal cells.

(c)(i)(I) Varicella: transmission, course and diagnosis

The probable agent is varicella-zoster virus (human herpesvirus 3), causing chickenpox. Transmission occurs via airborne aerosols and respiratory droplets or direct contact with infectious vesicular fluid; it is highly contagious (secondary attack rate about 90% in susceptible household contacts), and the patient is infectious from 1–2 days before the rash until all lesions have crusted. The incubation period is 10–21 days (usually 14–16). Lesions appear in successive crops, so macules, papules, vesicles and crusts coexist (pleomorphism); the typical centripetal distribution is densest on the trunk.

Pathogenesis and course (flowchart below):

Laboratory Diagnosis:

1. Tzanck smear of the vesicle base demonstrating multinucleated giant cells (Cowdry type A intranuclear inclusions are seen on histology); it does not distinguish VZV from herpes simplex.
2. Real-time PCR detecting Varicella Zoster Virus (VZV) DNA in vesicular scrapings.
3. Direct Fluorescent Antibody (DFA) staining of vesicular base exudates. Serology (VZV IgM for recent infection, IgG to establish immunity) and viral culture are other options.

(c)(i)(II) Post-exposure preventive 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 developed varicella from 5 days before to 2 days after delivery, and premature infants.
3. Chemoprophylaxis: oral acyclovir (or valacyclovir) given from day 7 to 10 after exposure for 7 days is an alternative when vaccine or VZIG is contraindicated or unavailable.
4. Infection control: isolation of the patient with airborne and contact precautions until all lesions crust; exclusion from school; identification of susceptible contacts; and routine two-dose varicella vaccination (not yet in India's UIP, but recommended by IAP).

(c)(ii) Malarial parasites in India and smear findings

The species found in India are Plasmodium vivax and Plasmodium falciparum, which together account for almost all cases (P. falciparum predominates in the forested tribal belts of Odisha, Chhattisgarh, Jharkhand and the North-East, and P. vivax in plains and urban areas), with Plasmodium malariae focally (Odisha), sporadic Plasmodium ovale, and the zoonotic Plasmodium knowlesi reported from the Andaman and Nicobar Islands.

Plasmodium falciparum is notoriously responsible for life-threatening complications, including cerebral malaria, acute kidney injury, blackwater fever (massive intravascular haemolysis with haemoglobinuria), 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.
• Plasmodium ovale: enlarged, oval RBCs with fimbriated edges and James's dots; schizonts with about 8 merozoites.
• Plasmodium knowlesi: rings resemble P. falciparum and later forms resemble P. malariae band forms, with a 24-hour cycle and high parasitaemia; PCR is needed for confirmation.

Thick smears are used to detect parasites and estimate density, and thin smears to identify the species; RDTs detecting HRP-2 (P. falciparum) and pLDH (pan-species) are used at the field level.