Soft Nails After Treatment With Aromatic Retinoids

A 62-year-old man with psoriasis treated with 25 mg of oral etretinate three times daily for two months developed soft, depressed proximal zones on his fingernails and toenails, indicating inadequate keratinization. This defect in the keratinization process, which is the primary target of aromatic retinoids, had not been previously reported. The rate of nail growth was unaffected, but the nail plate in the affected areas was not fully keratinized, as confirmed by a biopsy. This case highlighted a novel side effect of aromatic retinoid treatment.