Slowly progressive d-bifunctional protein deficiency with survival to adulthood diagnosed by whole-exome sequencing.

d-Bifunctional protein (DBP) deficiency is an autosomal recessive disorder of peroxisomal fatty acid oxidation caused by mutations in HSD17B4. It is typically fatal by the age of two years with symptom onset during the neonatal period, and survival until late childhood is rare. We herein report the case of a patient with DBP deficiency surviving until adulthood, who showed severe sensorineural deafness, disturbances in language acquisition, slowly progressive cerebellar ataxia, and peripheral neuropathy.