Examkin

Question

Difficulty: MediumPediatric Hematology and Oncology

A 66-year-old boy is brought to the clinic by his parents due to fatigue and yellowish discoloration of his eyes for the past 33 days. He had a mild upper respiratory tract infection one week ago. His past medical history is unremarkable, and his immunizations are up to date. Family history is notable for a paternal aunt who underwent an unexplained splenectomy in her twenties. Vital signs are within normal limits. Physical examination reveals scleral icterus, pale conjunctivae, and a palpable spleen edge 4 cm4 \text{ cm} below the left costal margin. Laboratory studies show the following:

TestResult
Hemoglobin7.8 g/dL7.8 \text{ g/dL}
Mean corpuscular volume80 fL80 \text{ fL}
Mean corpuscular hemoglobin concentration37.5 g/dL37.5 \text{ g/dL}
Reticulocyte count9%9\%
Platelet count240,000/mm3240,000/\text{mm}^3
Leukocyte count8,500/mm38,500/\text{mm}^3
Total bilirubin4.2 mg/dL4.2 \text{ mg/dL}
Direct bilirubin0.4 mg/dL0.4 \text{ mg/dL}

Direct antiglobulin (Coombs) testing is negative.

Which of the following is the most appropriate next step in diagnostic evaluation?

  1. Eosin-5-maleimide binding testAnswer
  2. B
    High-performance liquid chromatography of hemoglobin
  3. C
    Bone marrow aspiration and biopsy
  4. D
    Glucose-6-phosphate dehydrogenase enzyme assay
  5. E
    Reassurance and repeat complete blood count in one month

Answer

Eosin-5-maleimide binding test
The correct answer identifies the eosin-5-maleimide binding test. The patient's presentation of normocytic anemia, elevated mean corpuscular hemoglobin concentration (MCHC), reticulocytosis, indirect hyperbilirubinemia, splenomegaly, and a family history of splenectomy strongly suggests hereditary spherocytosis (HS). The elevated MCHC (>36 g/dL>36 \text{ g/dL}) is particularly characteristic, resulting from cellular dehydration and membrane loss. Following a negative direct Coombs test (which rules out autoimmune hemolytic anemia), the diagnosis of HS is confirmed using the eosin-5-maleimide (EMA) binding test or an osmotic fragility test.

Step-by-Step Solution

1
Analyze the patient's clinical presentation and family history.
The patient has jaundice, symptomatic anemia, splenomegaly, and a family history of splenectomy following a viral infection, suggesting a hereditary hemolytic anemia.
Identifying the pattern of inheritance and physical findings narrows the differential diagnosis to congenital causes of hemolysis.
2
Evaluate the laboratory data.
Labs show a normocytic anemia, elevated MCHC (37.5 g/dL37.5 \text{ g/dL}), and an appropriate reticulocyte response (9%9\%) with a negative direct Coombs test.
The MCHC is classically elevated in hereditary spherocytosis due to cellular dehydration, while the negative Coombs test rules out an autoimmune etiology.
3
Determine the appropriate confirmatory test.
The eosin-5-maleimide (EMA) binding test is selected to confirm the diagnosis.
EMA binding testing is highly sensitive and specific for detecting the decreased membrane proteins characteristic of hereditary spherocytosis.

Key Concept

Hereditary spherocytosis typically presents with hemolytic anemia, jaundice, splenomegaly, and an elevated MCHC; diagnosis is confirmed with an eosin-5-maleimide binding test or osmotic fragility test.
Rate this question

Topics

Pediatric Hematology and Oncology

More questions from this topic