SC5D (sterol-C5-desaturase) catalyzes the penultimate step of cholesterol biosynthesis, converting lathosterol to 7-dehydrocholesterol (7-DHC) 1. This enzyme is an integral membrane protein located on chromosome 11.2-24.3 2 and is expressed across multiple tissues, with hepatic expression regulated by cholesterol levels through suppression of promoter activity 2. Beyond cholesterol synthesis, SC5D plays a critical role in ferroptosis regulation. 7-DHC, the product of SC5D, functions as a natural anti-ferroptotic metabolite by using its conjugated diene structure to prevent phospholipid autoxidation and shield plasma and mitochondrial membranes from lipid peroxidation 3. SC5D acts as a ferroptosis suppressor, opposing DHCR7 which promotes ferroptosis sensitivity 3. SC5D mutations cause lathosterolosis, an autosomal recessive malformation syndrome characterized by lathosterol accumulation and cholesterol deficiency 4. In lathosterolosis, impaired SC5D activity disrupts multiple pathways including isoprenoid metabolism, apoptosis, and protein biosynthesis in developing neural tissue, leading to cognitive deficits and developmental abnormalities 4. SC5D expression is also subject to post-transcriptional regulation by miR-7, which modulates cholesterol homeostasis 5.