Erythropoietic protoporphyria, heterozygous cystinuria, and reduced peptidase A activity in a patient with 46,XX/46,XX,18q--mosaicism.

An interesting patient with a deletion of the long arm of chromosome 18 is presented. Her symptoms are severe in comparison with some other 18q--patients, yet she was found to have a mosaicism with a normal 46,XX karyotype in about 20% of her cultured lymphocytes. In addition, she had erythropoietic protoporphyria, was heterozygous for type II or III cystinuria, and had reduced levels of peptidase A activity. Detailed studied on the patient, her family, and two additional 18q--patients suggest that the association with erythropoietic protoporphyria is coincidental and that the cystinuria gene was inherited from the patient's father. The reduced peptidase A activity, however, supports earlier observations that the peptidase A locus maps in the q22 to terminus region of chromosome 18.