Alopecia universalis congenita (ALUNC) is a rare disorder characterized by generalized absence of hair at or shortly after birth. There are various forms of this condition, with inheritance showing autosomal recessive, dominant or even X-linked forms. However, the autosomal recessive form of this condition is the most common, and also the most severe form of the disease. Patients with this recessive form exhibit a complete absence of hair development, affecting all scalp and body hair. Affected individuals may show a broad spectrum of follicle alterations, ranging from absence of hair in the follicles to complete absence of the hair follicles themselves. Not only are the scalp hairs affected, but so are the axillary and pubic regions, eyebrows, and eyelashes. Neonates may have a few sparse hairs at the crown of head, which fall off within a few weeks and never regrow. The skin is otherwise unaffected, as evidenced by the unremarkable dermis and epidermis seen upon biopsy of the skin.
Linkage analysis was used to map the gene responsible for the autosomal recessive alopecia universalis, which pointed towards the short arm of chromosome 8. The locus, initially designated as ALUNC, was later revealed to carry a gene coding for a nuclear receptor co-repressor called the hairless gene (HR), which in its mutated form has been found to be responsible for the pathogenesis of the disease condition.