More Than Just Mosquito Bites: A Travel-Associated Case of Cutaneous Small-Vessel Vasculitis

A 39-year-old man presented with a bilateral lower limb pruritic and purpuric rash following travel to Chongqing, China. He was initially treated for cellulitis abroad. On arrival, his rash was noted, and the initial workup revealed raised inflammatory markers with a CRP of 252 mg/L and an ESR of 80 mm/hr. Examination of the lower limb reveals symmetrical, non-blanchable purpuric plaques with post-inflammatory hyperpigmentation. He was admitted for further inpatient treatment. Serological workup for autoimmune vasculitis was negative. Urine phase contrast microscopy showed 12% dysmorphic red blood cells, below the threshold typically seen in glomerular bleeding. A punch biopsy revealed minimal, superficial perivascular lymphocytic infiltrate without classic vasculitic features, likely due to timing post-acute inflammation. The clinical workup and examination findings support a diagnosis of post-infectious cutaneous small-vessel vasculitis (CSVV). This case demonstrates the classic distribution and morphology of CSVV. Early recognition of CSVV facilitates prompt systemic evaluation and discontinuation of potential triggers and avoids unnecessary antibiotic use.