Desmosterolosis (OMIM #602398) is a ultra-rare autosomal recessive disorder characterized by multiple congenital anomalies and elevated levels of the cholesterol precursor desmosterol. It results from a defect in the enzyme 3-beta-hydroxysterol delta-24-reductase (DHCR24), which plays a key role in the cholesterol biosynthesis pathway. A deficiency in this enzyme leads to increased levels of desmosterol. Cholesterol homeostasis is critical for normal growth and development. In addition to being an essential membrane lipid, cholesterol is also a precursor for numerous biological molecules, including steroid hormones, neuroactive steroids, oxysterols, and bile acids (1). In general, inborn errors in cholesterol synthesis lead to both a deficiency of cholesterol and a potential accumulation of bioactive or toxic sterol precursors. Desmosterolosis, one of these disorders, was first described by FitzPatrick et al. in 1997 (2). To date, only a limited number of cases have been reported in the literature (2, 3, 4, 5, 6, 7, 8, 9).

Here, we present a three-year-old female patient who was diagnosed with desmosterolosis and had compound heterozygous variants in the DHCR24 gene and clinical features, including agenesis of the corpus callosum, hypotonia, and developmental delay. To our knowledge, this is the first reported case of desmosterolosis in a Turkish patient.