D-Bifunctional Protein Deficiency (HSD17B4)
D-Bifunctional protein deficiency is an autosomal recessive, pan-ethnic disorder resulting from pathogenic variants in the gene HSD17B4. Onset is at birth. Clinical features vary between patients, but the most frequently observed features include hypotonia, seizures, failure to thrive and lack of developmental progress. Other commonly seen features include a characteristic facial appearance, and severe brain, liver and kidney abnormalities. Most patients die in infancy. Rarely, a mild form of HSD17B4 deficiency has been reported in adults and has been characterized by neurodegeneration, hearing loss and infertility; these patients tend to have at least one mild missense variant. However, it is currently not possible to predict the severity of the phenotype based on genotype.
For information about carrier frequency and residual risk, please see the residual risk table.