Keratoacanthoma seen with hidradenitis suppurativa: A case report

Hidradenitis suppurativa (HS) is considered a primary disease of the hair follicle. The chronic occlusion of the follicular pilosebaceous unit and an associated immune response appears to be the main causes. The chronic, active, and poorly controlled disease may lead to several complications such as scars, contractures, lymphedema, osteomyelitis, and squamous cell carcinoma (SCC). We report here a 33-year-old male with HS who developed keratoacanthoma while on secukinumab treatment. The tumor representing 2 weeks of evolution in an area affected by HS (lower abdomen) was followed up after histopathological confirmation. Almost complete spontaneous regression was observed at the subsequent visits. As far as we are aware, solitary keratoacanthoma associated with HS has not been previously described. Our case shows that squamous differentiation is not limited to SCC and can develop from any scar tissue outside the anogenital region in patients with HS. Thus, the case presented here emphasizes the necessity of careful examination in scar areas as well as inflammatory lesions in HS.