Abstract:  Melanonychia is a black, tan, or brown streak within the nail plate subsequent to activation of melanocytes in the nail matrix. We present a case of a Haitian girl who presented with transverse melanonychia involving all 10 fingernails in the setting of hyperthyroidism and acute liver injury. Melanonychia has been described only one time in the literature in the setting of hyperthyroidism though this patient also underwent radium treatment which could have led to nail changes.