Hairy cell leukemia is notable for staining tartrate-resistant acid phosphatase positive (TRAP positive) and for having hairy cytoplasmic projections [FA2020 p432].
If you did not know this, you could eliminate other answers based on the stem:
Lymphomas would have swollen lymph nodes
It mentions the lymphocytes as the issue and he has lymphocytosis, so you can eliminate the myelogenous leukemias and focus on the ones from the lymphocytic cell lines
Acute lymphoblastic leukemia most commonly occurs in children and is associated with immature B/T-cells that are TdT+, so you can eliminate this
Chronic myelogenous leukemia is slowly progressing and associated with smudge cells, so it also does not match the descriptors.
baja_blastFor the last bullet, I believe OP meant CLL instead of CML. +1
fatboyslimI initially chose hairy cell leukemia but then when I re-read the vignette I was thrown off by the LOW WBC count. I thought to myself leukemia definitely will have high WBCs, and switched it to mononucleosis lol.
TLDR: hairy cell leukemia can present with LOW WBC!+
submitted by โcassdawg(1780)
Hairy cell leukemia is notable for staining tartrate-resistant acid phosphatase positive (TRAP positive) and for having hairy cytoplasmic projections [FA2020 p432].
If you did not know this, you could eliminate other answers based on the stem: