Patients with anorexia nervosa have an increased burden of rare, damaging mutations in the BBOX1 gene.

BACKGROUND

People with anorexia nervosa (AN) exhibit a strong aversion to eating calorically dense foods, especially those high in fat. It has previously been reported that these patients display altered metabolism of fatty acids, however it is unclear if these metabolic disturbances represent a primary biological substrate underlying predisposition to restrictive eating behaviors or occur secondarily to malnutrition.

METHODS

We report the frequency of rare (minor allele frequency < 1%), damaging (CADD > 15) mutations in the BBOX1 gene of 183 patients with anorexia nervosa who received whole exome sequencing (WES) as part of their psychiatric evaluation. The observed frequency from our cohort was then compared to the rate of rare, damaging mutations in BBOX1 reported in the gnomAD database to determine if there was an excessive burden of damaging mutations.

RESULTS

The 11-27127338-G-A single nucleotide polymorphism in BBOX1 was observed to be shared by four sisters with a history of AN. Subsequent analysis found that this variant was also present in five out of 182 patients who had WES results. Six more unrelated patients out of 182 were found to have one of five additional rare, damaging mutations in BBOX1. In total, 12 out of 183 patients (6.6%) with AN were found to have a rare, damaging mutation in BBOX1 compared to an expected count of 4.4 (2.4%) from the gnomAD database (odds ratio 2.86; p = 0.0117).

CONCLUSIONS

Patients with a history of AN have an increased burden of rare, damaging mutations in the BBOX1 gene. Because BBOX1 is required for synthesis of carnitine, a nutrient required for transport of long-chain fatty acids into the mitochondria for beta-oxidation, this finding suggests that impaired utilization of long-chain fatty acids may increase the risk of developing AN in a subset of patients. Identification of this group of patients by genetic or blood testing may lead to improved treatment outcomes and/or secondary prevention of relapse.