Desmosterolosis

Desmosterolosis is a very rare sterol biosynthesis disorder characterized by multiple congenital anomalies, failure to thrive, and intellectual disability, with elevated levels of desmosterol.

Epidemiology

Only 9 cases have been reported in the literature to date.

Clinical description

Desmosterolosis presents at birth with growth restriction, spasticity with variable degrees of hand contractures, either microcephaly or relative macrocephaly, and microretrognathia. Transient neonatal seizures, nystagmus, strabismus and failure to thrive are also seen in most cases. Intellectual disability occurs in all patients and is first noted by delayed milestones for speech and adaptive, fine and gross motor development. Less common manifestations reported include hirsutism, facial dysmorphism (downslanting palpebral fissures, bilateral epicanthal folds, submucous cleft palate, and thick alveolar ridges), sensorineural hearing loss, patent arterial duct, ambiguous genitalia, bilateral clubfeet, muscle wasting, and cutis aplasia. Optic atrophy, corpus callosum agenesis and loss of white matter are also noted.

Etiology

Desmosterolosis is due to mutations in the DHCR24 gene (1p32.3) encoding 3-beta-hydroxysterol delta-24-reductase. This enzyme catalyzes the conversion of desmosterol (the cholesterol precursor) to cholesterol, which is highly involved in embryonic development and morphogenesis. Reduced enzyme activity leads to the accumulation of desmosterol and a lack of cholesterol, disrupting antenatal and postnatal development.

Genetic counseling

Desmosterolosis is inherited in an autosomal recessive manner and genetic counseling is possible.