Examkin

Question

Difficulty: HardFormulating a Differential Diagnosis

A 52-year-old man presents to the clinic with a 2-month history of worsening fatigue, early satiety, and left upper quadrant abdominal discomfort. He has no other significant past medical history and takes no medications. Vital signs are within normal limits. Physical examination is notable for massive splenomegaly extending to the umbilicus. No hepatomegaly or peripheral lymphadenopathy is appreciated.

Laboratory studies show:
Leukocyte count: 85,000/mm³ (neutrophils 55%, bands 15%, metamyelocytes 10%, myelocytes 12%, promyelocytes 3%, blasts 2%, basophils 3%)
Hemoglobin: 10.5 g/dL
Platelets: 450,000/mm³

Based on the clinical presentation and laboratory findings, arrange the following diagnoses from highest to lowest pre-test probability.

  1. 1Chronic myeloid leukemia
  2. 2Primary myelofibrosis
  3. 3Leukemoid reaction
  4. 4Acute myeloid leukemia
  5. 5Chronic lymphocytic leukemia

Answer

The correct order from most to least likely is: Chronic myeloid leukemia, Primary myelofibrosis, Leukemoid reaction, Acute myeloid leukemia, and Chronic lymphocytic leukemia.
The patient's presentation of massive splenomegaly, massive leukocytosis with a full spectrum of granulocytic precursors, and absolute basophilia is the classic presentation of Chronic myeloid leukemia. The other options either lack the exact combination of these findings, present acutely, or involve different cell lineages.

Step-by-Step Solution

1
Analyze the physical examination findings.
The patient has massive splenomegaly, which narrows the differential diagnosis significantly toward myeloproliferative neoplasms, particularly chronic myeloid leukemia and primary myelofibrosis, while making reactive causes less likely.
Massive splenomegaly (extending to the umbilicus) is a key diagnostic anchor that rules out many causes of mild to moderate splenomegaly.
2
Evaluate the complete blood count and differential.
There is profound leukocytosis (85,000/mm³) with a full spectrum of myeloid maturation, absolute basophilia, mild anemia, and high-normal to elevated platelets.
This specific peripheral blood profile distinguishes a primary myeloproliferative process from reactive states (which lack basophilia) or acute leukemias (which feature a leukemic hiatus).
3
Synthesize findings to rank the differentials.
Chronic myeloid leukemia is the primary consideration. Primary myelofibrosis is a strong second due to the massive spleen. Leukemoid reaction is ranked lower due to the lack of an inciting event and absence of basophilia. Acute leukemias and lymphoid disorders are the least likely due to incompatible lab profiles.
Systematic ranking based on epidemiological likelihood and exact matching of objective data prevents premature diagnostic closure.

Key Concept

The differential diagnosis of massive splenomegaly with marked leukocytosis depends heavily on the leukocyte differential; a full spectrum of granulocytic precursors with absolute basophilia strongly indicates Chronic Myeloid Leukemia (CML), distinguishing it from leukemoid reactions and other myeloproliferative neoplasms.
Estimated Time:1m 30s
Rate this question

Topics

Formulating a Differential Diagnosis

More questions from this topic