An Atypical Pediatric Dermatologic Presentation Unmasking an Unexpected Systemic Diagnosis: A Diagnostic Challenge.

Dermatologic and musculoskeletal presentations in pediatric patients can pose significant diagnostic challenges, particularly when findings are atypical, persistent, and resistant to therapy. We present a diagnostically complex case of a 13-year-old male with a history of multiple psychiatric comorbidities who developed progressive bilateral pedal edema, bullous lower extremity lesions with excoriations, and severe pain, all symptoms seemingly refractory to antibiotics. Despite initial concern for skin and soft-tissue infection, symptoms persisted, prompting inpatient evaluation and an expanded serologic workup. Screening for immunologic and infectious causes, including human immunodeficiency virus (HIV) and sexually transmitted infections, revealed a new diagnosis of HIV-1 acquired through non-perinatal transmission. The patient was concurrently diagnosed with atypical IgA vasculitis, raising consideration of infectious versus drug-related triggers based on his medication regimen. Although vasculitis is uncommon in HIV-positive patients, and IgA vasculitis is even rarer, this case emphasizes the importance of a broad differential diagnosis in pediatric patients with multisystem involvement. Ultimately, close attention to atypical presentations can ensure timely diagnoses and better care for patients facing similarly complex conditions.