A 5-year-old girl with progressive pallor and recurrent infections has pancytopenia on CBC. Examination reveals bilateral thumb hypoplasia, short stature, café au lait spots, and microcephaly. Bone marrow is hypocellular. What is the definitive diagnostic test?

• A Detection of parvovirus B19 DNA by PCR
• B Elevated fetal hemoglobin on electrophoresis
• C Increased chromosomal breakage of lymphocytes on exposure to diepoxybutane ✓
• D Absence of radii on skeletal survey

Explanation

Fanconi anemia is the commonest inherited bone marrow failure syndrome, caused by defective DNA repair, and classically combines pancytopenia with radial ray anomalies, short stature, and skin pigmentation changes. Diagnosis is confirmed by demonstrating increased chromosomal breakage after exposure to diepoxybutane or mitomycin A. Elevated HbF occurs but is nonspecific, parvovirus causes transient pure red cell aplasia, and absent radii alone does not establish marrow failure.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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