Epidermal nevus syndrome associated with hypophosphatemic rickets.

Epidermal Nevus Syndrome (ENS) is characterized by epidermal nevi associated with abnormalities involving the nervous, skeletal, and other systems. Rarely, hypophosphatemic rickets has been observed in association with epidermal nevi. A patient with ENS with right-sided serpiginous skin lesions, generalized weakness, and diffuse osteopenia associated with hypophosphatemic rickets is described. Medical management was enough to correct the clinical picture. The pathogenic mechanism involved in the onset of hypophosphatemic rickets in ENS is not fully clarified. Different studies suggest that phosphaturia, caused by circulating factor(s), called "phosphatonin(s)," may be secreted by an epidermal nevus. The nature of the phosphaturic factor(s) is not well understood, but elevated levels of circulating FGF-23 were recently reported in one patient with hypophosphatemic rickets. The authors suggest that serum FGF-23 measurement be included in the workup of this kind of rickets because there is growing evidence that in these situations the epidermal nevi produce a phosphaturic factor.