Ectopic Presentation of Hidradenitis Suppurativa on the Dorsal Foot with Secondary Bacterial Infection: A Case Report

Abstract

Background: Hidradenitis suppurativa (HS) is a chronic, relapsing inflammatory skin disorder most commonly affecting apocrine gland-rich regions such as the axillae, groin, and perianal areas. Ectopic HS, occurring outside these conventional sites, is exceptionally rare, particularly on the dorsal foot, with only two documented cases in the literature. Here, we present a third case of ectopic HS on the dorsal foot, complicated by secondary bacterial infection, and discuss its diagnostic and therapeutic implications.

Case Presentation: A 67-year-old male with a history of hypertension, hyperlipidemia, and a 57 pack-year smoking history presented with a five-day history of painful swelling on the left dorsal foot. Clinical examination revealed a violaceous, tender bi-nodular lesion without drainage. Notably, the patient reported a prior axillary lesion consistent with HS. Imaging revealed subcutaneous edema and a bilobed lesion; wound cultures isolated methicillin-sensitive Staphylococcus aureus (MSSA). Following surgical drainage and intravenous antibiotics, two deep tissue punch biopsies confirmed ulceration with suppurative inflammation. Clinical correlation supported a diagnosis of ectopic HS (Hurley stage I) with secondary infection. The lesion resolved fully by six-week follow-up.

Discussion: This case highlights the diagnostic challenges of ectopic HS, particularly in apocrine-deficient areas such as the dorsal foot. Prior axillary involvement, mechanical friction, and smoking likely contributed to pathogenesis. The presence of MSSA further complicated management, necessitating a multidisciplinary approach. Our findings reinforce a follicular occlusion-centered model of HS pathogenesis and highlight the need for clinician awareness of atypical presentations to facilitate early diagnosis and intervention.