A 3-year-old boy presents with a scaly, seborrhea-like rash over the scalp and trunk that failed topical steroids, along with a tender swelling behind the right ear. Skull radiograph shows a well-defined lytic lesion with a beveled edge. Biopsy of the lesion shows cells positive for CD1a and S-100 with Birbeck granules on electron microscopy. Which additional finding should be specifically sought to assess prognosis?
- A Positive urine VMA
- B Presence of eosinophilia on peripheral smear
- C Elevated serum alkaline phosphatase
- D Hepatosplenomegaly indicating multisystem involvement ✓
Explanation
The triad of seborrheic dermatitis-like rash, lytic skull lesions, and CD1a-positive cells with Birbeck granules establishes Langerhans cell histiocytosis. Prognosis depends chiefly on whether disease is single-system or multisystem, so hepatosplenomegaly, marrow involvement, and lung lesions must be actively sought; age under 2 years with multisystem and risk-organ involvement carries worse outcomes. Eosinophilia is nonspecific, alkaline phosphatase points to bone remodeling rather than this lesion, and urinary VMA screens for neuroblastoma, a different tumor altogether.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.