What Your Test Results Mean:

Carriers typically show no symptoms of D-bifunctional protein deficiency; however, carriers are at an increased risk of having a child with D-bifunctional protein deficiency. Risk for the current or future pregnancies is dependent on your partner’s carrier status. Carrier testing of your partner is recommended in addition to consultation with a genetic counselor.

Disease Explained:

D-bifunctional protein deficiency is an inherited condition that inhibits the cell’s ability to break down fatty acids. This leads to severe neurodegeneration beginning in early infancy. Newborns affected by D-bifunctional protein deficiency have poor muscle tone and seizures. These symptoms continue and these babies typically reach very few developmental milestones. They often have severe mental and physical retardation and develop visual and hearing impairment. Most affected individuals die before reaching age two. There is no cure for D-bifunctional protein deficiency but research is ongoing to determine whether stem cell transplant may be beneficial.

How the Genetics Works:

D-bifunctional protein deficiency is an autosomal recessive disorder caused by pathogenic variants in the HSD17B4 gene. In general, individuals have two copies of the HSD17B4 gene. Carriers of D-bifunctional protein deficiency have a single variant in one copy of the HSD17B4 gene while individuals with D-bifunctional protein deficiency have variants in both copies of their genes, one inherited from each parent. Risk for two carriers to have a child with the disorder is 25%.