Can median nail dystrophy be an adverse effect of alitretinoin treatment?

Median canaliform nail dystrophy is an unusual condition of the nail, most often affecting the thumb (1). It is characterized by a longitudinal split or canal in the nail with small transversal fissures, in a fir-tree configuration. The condition is diagnosed based on its clinical features (2, 3). While the underlying mechanism is unknown, it has been suggested that median canaliform nail dystrophy is the result of a temporary defect in the nail matrix, following dyskeratinization or focal infection, or alternatively is due to self-inflicted trauma to the nail or nail bed. Familial cases have been reported (2, 3). Spontaneous remission is often seen, but the condition can be recurrent (1). Three case reports of median canaliform nail dys-trophy as an adverse effect of acne treatment with isotretinoin (13-cis-retinoic acid) have been published (3–5). Alitretinoin (9-cis-retinoic acid), on the other hand, is used in the treatment of severe chronic hand eczema (6–8). We report here a case of median canali-form nail dystrophy that developed in a patient treated with alitretinoin for severe hand eczema. A 53-year-old man, with a history of chronic dyshidrotic and keratotic hand and foot eczema, developed nail changes after receiving alitretinoin treatment for 16 months. The changes were most prominent on the thumbnails, where he presented median longitudinal ridging and splitting with transversal fissures. There were both horizontal and fir-tree shaped fissures among the transversal changes. Minor nail plate dystrophy was seen on the other nails, and all nails on both hands had ragged cuticles and enlarged lunulae. The patient's eczema was diagnosed in 1998 and initial treatment with topical and systemic steroids, azathioprine, metho-trexate, acitretin, cyclosporine or mycophenolate mofetil had either adverse effects or worked insufficiently. In 2008, alitreti-noin became available on the Danish market and it was prescribed to the patient in 2009. He initially received 30 mg daily, but developed adverse effects, such as headache, vertigo and universal dry skin with pruritus, after less than 1 month's treatment. A reduction in the dose was tried, first to 30 mg every third day, and later to 10 mg daily, but the adverse effects remained and the treatment was discontinued after 6 months. In 2012, the patient's eczema worsened and alitretinoin was reintroduced at a daily dose of 10 mg. After being treated with alitretinoin for 16 months, the patient developed the characteristic nail findings, which were diagnosed as median canaliform nail dystrophy (Fig. 1A). …