We present 3 patients with Pterygium unguium, a not so common dystrophy of the nail. Their diagnoses are: Epidermolysis bullosa aquisita, junctional Epidermolysis bullosa, benign form and Nail-Patella Syndrome, the last one being associated with multiple osteo-arthro dysplasies and glomerulonephritis with membranar deposits. We discuss about the pathogenesis of the diseases mentioned above and its implication in the development of pterygium unguium as well as the importance of onychodystrophies for the physician.