Carbamoyl phosphate synthetase 1 (CPS1) deficiency (OMIM#237300) is a rare inherited disorder due to complete or partial lack of the CPS1 enzyme. Polymyositis is a relatively rare systemic inflammator Show more
Carbamoyl phosphate synthetase 1 (CPS1) deficiency (OMIM#237300) is a rare inherited disorder due to complete or partial lack of the CPS1 enzyme. Polymyositis is a relatively rare systemic inflammatory autoimmune disease. Here, we report a 59-year-old Japanese woman diagnosed with late-onset CPS1 deficiency during polymyositis treatment. The polymyositis appeared two years before the diagnosis of CPS1 deficiency. Prednisolone (PSL) at 35 mg/day initial dosage, promptly alleviated the symptoms. However, the patient, without apparent cause, suddenly developed confusion progressing to unconsciousness and coma. Upon admission, the patient's plasma ammonia levels were 458 μg/dL (269 μM). Plasma amino acid analysis revealed decreased citrulline levels and elevated glutamine levels. Genetic analysis of Show less