Covello et al. (1998) described 2 unrelated kindreds with the identical missense arg94-to-cys (R94C) mutation in the 1A domain of keratin-17. However, whereas affected members of 1 kindred had the classic features of Jackson-Lawler pachyonychia congenita (PC2; 167210), affected persons in the other family had the steatocystoma multiplex phenotype (184500). The PC2 family consisted of affected mother and son; the affected steatocystoma multiplex family had affected mother, son, and daughter. The proband in the first family had a history of subcutaneous yellow nodules on the flexor surfaces of the arms, abdomen, and legs since puberty. She also had thickened nails of the feet. In the steatocystoma multiplex family, the 41-year-old Dutch Caucasian mother presented at an outpatient clinic because of what she described as 'acne present from puberty.' The number of lesions had increased with age; in addition to the face, lesions were present on the abdomen, arms, and legs. Her 4-year-old daughter and 11-year-old son were developing similar skin problems. Multiple nodules with varying diameter were found in the areas mentioned. None of the affected persons showed any nail changes or any other skin, hair, or mucosal abnormalities.
