Trichorrhexis nodosa secondary to argininosuccinicaciduria.

Argininosuccinicaciduria is a rare metabolic disorder of the urea cycle associated with the inability to excrete nitrogenous waste in the form of urea. Along with low serum arginine, hepatomegaly, and mental retardation, congenital trichorrhexis nodosa is a distinguishing feature of the disorder. We present a 3.5-year-old girl diagnosed with argininosuccinicaciduria who presented to the dermatology clinic with hair thinning and loss since birth. Microscopic evaluation revealed nodular swellings on the hair shafts and frayed cortical fibers consistent with the diagnosis of trichorrhexis nodosa occurring in the setting of argininosuccinicaciduria.