The correct answer is A. Genetic testing for STAT3 and DOCK8 mutations.

This presentation is most consistent with hyper-IgE syndrome (HIES), which is characterized by severe eczema, recurrent staphylococcal and viral skin infections, and the development of “cold” (non-tender) abscesses and subcutaneous nodules due to impaired inflammation. Facial eczema with crusted papulopustules in early childhood plus deep, painless thigh nodules strongly raises suspicion for HIES. Genetic testing for STAT3 and DOCK8 mutations would establish the diagnosis, as STAT3 deficiency (autosomal dominant) and DOCK8 deficiency (autosomal recessive) account for most cases. STAT3-HIES is more commonly associated with skeletal abnormalities and “cold abscesses,” while DOCK8-HIES more prominently features recurrent viral infections, food allergies, and higher malignancy risk.

SPINK5 mutation testing is used to diagnose Netherton syndrome, which presents with congenital ichthyosiform erythroderma, trichorrhexis invaginata, and atopy. Measuring immunoglobulin E levels may support the diagnosis of HIES, as these children often have very high IgE, but this is not diagnostic and is insufficient alone. Serum zinc levels would be appropriate when evaluating for acrodermatitis enteropathica, which presents with periorificial dermatitis, diarrhea, and alopecia. Flow cytometry for CD18 expression evaluates for leukocyte adhesion deficiency (LAD), which presents with delayed cord separation and recurrent infections without pus formation due to neutrophil trafficking defects.

References:Gracci S, Novelli T, D’Elios S, Bernardini R, Peroni D. Hyper IgE syndromes. Curr Pediatr Rev. 2024;20(3):253-264.

 

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