Case Presentation: A 12-year-old male with a history of hyperhidrosis presented to the emergency department with bilateral foot swelling, pain and fevers. The pain began two days prior to admission after spending several hours in wet shoes. The following day he developed fevers and his swelling and pain worsened such that he was no longer able to walk, prompting evaluation. Additional history obtained in the emergency department revealed a history of COVID infection 1 year prior and vaccination 3 weeks ago. On presentation, he was febrile and tachycardic. Physical exam was notable for bilateral erythematous conjunctiva, mild tenderness to palpation of the abdomen and bilateral scattered erythematous patches of the plantar aspect of his feet with mild edema. Laboratory evaluation was significant for a leukocytosis with neutrophil predominance and an elevated CRP of 7.8. He was started on cephalexin for presumed cellulitis, which he vomited. Due to the progression of his symptoms and inability to tolerate oral intake he was started on ceftriaxone and vancomycin and admitted to the hospital. Differential diagnosis at the time of admission included MIS-C, Kawasaki Disease, or cellulitis of bilateral feet, which seemed unlikely. Labs for MIS-C and Kawasaki Disease were reassuring. The following day, his rash evolved to bilateral plantar blanching erythematous patches and macules (pictured). His new rash findings and history led to a diagnosis of plantar eccrine hidradenitis. His fevers resolved and he was discharged home on over-the-counter pain medications. His symptoms soon fully resolved aside from some post-inflammatory plantar nodules.

Discussion: Idiopathic plantar eccrine hidradenitis tends to occur in children and adolescents during the spring and summer. It has been associated with hyperhidrosis, and typically occurs after a period of excessive moisture or prolonged physical activity in patients with blocked eccrine sweat glands. Presentation typically includes a characteristic bilateral, blanching, erythematous nodules and plaques on the soles of the feet and hands with systemic symptoms including fevers. Plantar eccrine hidradenitis is normally a clinical diagnosis, however confirmatory diagnosis can be made by observing neutrophils on biopsy. It is a self-limited illness, with the mainstay of treatment being symptomatic care, though topical steroids can be added in severe cases.

Conclusions: Plantar eccrine hidradenitis is an uncommon rash with a very good prognosis that initially can mimic other more serious etiologies. Clinicians should consider this diagnosis in febrile patients with prolonged exposure to wet environments who present with characteristic extremity findings.