Terra Firma-Forme Dermatosis Presenting With Unusual Features: A Case Report.

Terra firma-forme dermatosis (TFFD), also known as retention hyperkeratosis, is a benign cutaneous disorder characterized by dirt-like, brownish patches or plaques that are resistant to conventional hygiene practices, including washing with soap and water. It is due to delayed keratinocyte maturation and retention of melanin and sebum within a compact stratum corneum. Here we report a 25-year-old male who presented with a six-month history of a persistent, asymptomatic, gradually enlarging skin lesion over his chest. Skin examination revealed a large well-demarcated verrucous yellowish plaque on his chest. Clinical differential diagnoses included terra firma, dermatatitis neglecta, confluent and reticulated papillomatosis of Gaugorut and Cartuad (CARP), late onset epidermal nevus, verrucous xanthoma and acanthosis nigricans. A diagnostic wipe test using 70% isopropyl alcohol led to immediate and near-complete resolution of the plaques, supporting the diagnosis of terra firma-forme dermatosis. A punch biopsy was performed prior to doing the diagnostic wipe test with alcohol. It revealed lamellar hyperkeratosis, orthokeratotic, papillomatosis, acanthosis, with no significant dermal inflammation, findings consistent with TFFD.