Treatable fluctuating mental impairment in a patient with Bardet–Biedl syndrome

Abstract 

Bardet–Biedl syndrome (BBS) is an autosomal recessive disorder characterized by rod–cone dystrophy, polydactyly, central obesity, mental retardation, and hypogonadism. Although many organs are involved in BBS, hyperammonemia caused by portal hypertension has been reported previously in only a single patient. We describe the second such patient with BBS and hyperammonemia, associated with fluctuating mental impairment.

The patient was a 17-year-old boy with BBS. Esophageal, gastric, and rectal varices and mild hepatic dysfunction started to develop at 5 years of age. A liver biopsy showed dilated portal veins with mild fibrosis in portal tract. From the age of 17 years, he often had forced laughter with apparently normal consciousness. Laboratory examinations revealed hyperammonemia (112.2mg/ml). Oral medication lowered the blood ammonia level to 69.9mg/ml, reduced the frequency of forced laughter, and improved his IQ.

Patients with BBS may have additional diseases or conditions that affect mental status, such as hyperammonemia. Physicians should explore the underlying causes of these conditions and treat such patients, who already have a compromised quality of life.

Keywords: Bardet–Biedl syndrome, Hyperammonemia, Portal hypertension, Fluctuating mental impairment, Liver biopsy, MRI