Clinical Presentation of a Family Diagnosed With Marie Unna Hereditary Hypotrichosis 1 Caused by a Novel Variant in <scp> <i>HRURF</i> </scp>

Marie Unna hereditary hypotrichosis 1 (MUHH1) is a rare autosomal dominant condition characterized by the absence or scarcity of hair at birth with the growth of coarse, wiry, and unruly hair during childhood and progressive hair loss after puberty. This case report describes the clinical presentation of three Danish family members with congenital hypotrichosis with a new phenotypic variation marked by progressive scalp hair growth during adulthood in one of the members. A novel likely pathogenic variant c.105G>T (p.(*35Tyrext*?)) in HRURF, formerly known as U2HR, causing MUHH1 was identified. The findings contribute to the knowledge on pathogenic and phenotypic variation in MUHH1.