SNP Shot: Genomic Insights

D-bifunctional protein deficiency is a condition characterized by neurodegeneration that begins in infancy. Infants born with this deficiency typically exhibit hypotonia and seizures. The majority of affected infants fail to achieve typical developmental milestones. While some may initially demonstrate limited progress, such as tracking movement or head control, they soon experience developmental regression, losing these skills within a few months. As the condition progresses, individuals develop hyperreflexia, hypertonia, more frequent and severe seizures (epilepsy), and vision and hearing loss. Sadly, most children with D-bifunctional protein deficiency do not live beyond the age of two. A minority of individuals experience a milder form of the disorder. These individuals may acquire more advanced skills, like voluntary hand movements or unsupported sitting, before experiencing regression and may live longer than those with more severe symptoms.

Individuals with D-bifunctional protein deficiency can present with distinctive facial features, including a high forehead, hypertelorism, a long philtrum, and a high-arched palate. Affected infants might also have an unusually large fontanelle. Hepatomegaly is observed in approximately half of those affected. Due to overlapping features with Zellweger syndrome (a Zellweger spectrum disorder), D-bifunctional protein deficiency is sometimes referred to as pseudo-Zellweger syndrome.

Inheritance:

D-bifunctional protein deficiency follows an autosomal recessive inheritance pattern. This means that an individual must inherit a variant in both copies of the responsible gene to develop the condition. The parents of an affected individual each carry one copy of the altered gene but typically do not exhibit any symptoms themselves.