A 2-month-old infant is brought to your clinic with an extensive scaly rash on the scalp, which has been biopsied and shown to be Langerhans cell histiocytosis (LCH). You want to determine whether this patient has skin-only LCH or involvement of any of the 'high-risk' organs. The child has a normal CBC; normal liver enzymes and bilirubin; and a normal skeletal survey, skull films, and chest X ray. What other screening test will be important for finding involvement of a high-risk organ?
Correct Answer: D
Rationale: The correct answer is D: Serum albumin and total protein. In LCH, high-risk organ involvement includes the liver and spleen. Serum albumin and total protein levels can help assess liver function, as low levels may indicate liver involvement. A normal CBC, liver enzymes, and bilirubin do not rule out organ involvement, as LCH can affect organs without causing significant abnormalities in these tests. Reticulocyte count (A) is not relevant for assessing high-risk organ involvement in LCH. Erythrocyte sedimentation rate (B) is a nonspecific marker of inflammation and not specific for organ involvement. Alkaline phosphatase (C) is more indicative of bone or liver disease rather than specifically assessing high-risk organ involvement in LCH.