October 30, 2010

PLAB Question 24

A 38 year old male with Down's syndrome develops shortness of breath and diffuse epistaxis. On examination he is found to have generalised large lymph nodes and hepatosplenomegaly. There are diffuse petechiae and ecchymoses, on his skin.

A Romanovsky-stained smear of his bone marrow is most likely to demonstrate:

a) target cells
b) melanocytes
c) lymphoblasts with clumped chromatin
d) transitional epithelial cells
e) mast cell infiltration
f) neutropenia
g) Burr cells
h) squamous epithelial cells
i) anti-nuclear antibodies
j) clumps of neutrophils








ANSWER
The correct answer is C



Explanation
Acute leukemias are commoner in Down's syndrome. Experienced morphologists can reproducibly classify about 70% of acute leukemias as either ALL or AML by the blast appearance on Romanovsky-stained smears based on nuclear and cytoplasmic features.

The most important morphologic characteristic in identifying blasts is the nuclear chromatin pattern.

The chromatin in lymphoblasts is more clumped and irregularly distributed. The presence of nucleoli varies. Nucleoli may be indistinct or appear prominent because of chromatin condensation along the nucleolar and nuclear membranes.

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