Index of Suspicion

Case 1 Presentation

A 3½-year-old boy, who lives in the southeastern United States, is referred for evaluation of eosinophilia that was detected on laboratory tests performed during a routine health supervision visit. A few days ago, he had loose stools, without blood or mucus, associated with low-grade fever. He has no history of significant illness, allergies, respiratory symptoms, weight loss, sick contacts, or travel. He is not taking any medications. He lives with his mother, aunt, three siblings, four cousins, and two dogs in a rural area that has city water and sewage. He frequently plays outside the house.

Physical findings, including vital signs, are within normal limits except for some scratch marks on his trunk and extremities. His WBC count is 35×10³/mcL (35×10⁹/L) with 56% eosinophils (absolute eosinophil count [AEC] of 19.8×10³/mcL [19.8×10⁹/L]). The rest of the laboratory evaluation, including a metabolic panel and a C-reactive protein assessment, yields normal results. Stool examination for ova, cysts, and parasites shows negative results. Serum concentrations of immunoglobulin G (IgG), IgM, and IgA are normal, but the IgE value is elevated (1,358 international units/mL). Immunophenotyping for T and B lymphocytes and natural killer cells is within normal limits. Additional laboratory evaluation leads to the diagnosis.

Case 2 Presentation

A 17-year-old boy presents with a 1-day history of left arm swelling and pain from the mid-biceps to the forearm. He denies fever, trauma, or muscle strain, but does report having lifted weights last week. He has had a port wine stain since birth and underwent laser surgery at 3 months of age where it affected his face, but still has the stain on his left upper extremity. He drinks protein shakes but takes no medications, smokes one cigarette per week, and occasionally smokes marijuana, most recently 3 weeks ago. He has …