Hypotrichosis simplex can affect all body hair or be limited to the scalp. Usually patients with the scalp-limited form of hypotrichosis present with normal hair at birth; they experience a progressive, gradual loss of scalp hair beginning at ... Hypotrichosis simplex can affect all body hair or be limited to the scalp. Usually patients with the scalp-limited form of hypotrichosis present with normal hair at birth; they experience a progressive, gradual loss of scalp hair beginning at the middle of the first decade and leading to almost complete loss of scalp hair by the third decade. A few sparse, fine, short hairs remain in some individuals. Body hair, beard, eyebrows, axillary hair, teeth, and nails develop normally. Light and electron microscopy of hairs from early hypotrichosis simplex revealed no structural changes, whereas hairs from patients with advanced hypotrichosis showed focal areas of defective cuticular structure. Men and women are equally affected (summary by Betz et al., 2000). - Genetic Heterogeneity of Hypotrichosis Simplex of the Scalp Hypotrichosis simplex of the scalp-2 (HTSS2; 613981) is caused by mutation in the KRT74 gene (608248) on chromosome 12q13.
Hypotrichosis simplex of the scalp was first described by Toribio and Quinones (1974). They observed a large Spanish kindred with affected members in 8 generations. Affected children were normal at birth and in the first years of life. ... Hypotrichosis simplex of the scalp was first described by Toribio and Quinones (1974). They observed a large Spanish kindred with affected members in 8 generations. Affected children were normal at birth and in the first years of life. Between ages 5 and 12 years, retardation of hair growth was observed. Between ages 20 and 25 years, all affected persons, male and female, reached a terminal stage in which only a few sparse, fine, short hairs persisted on the scalp. There were no associated abnormalities of beard, eyebrows, axillary hair, teeth, or nails. In all earlier reported families, the disorder does not seem to have been limited to the scalp or present at birth. Hess and Uno (1991) described affected cases in 6 generations of a Caucasian family with 1 instance of male-to-male transmission. Hairs of the scalp were generally sparse and short of vellus type from childhood and thinned progressively with age. The family resembled those of Toribio and Quinones (1974) and Kohn and Metzker (1987) except that the 2 latter families showed normal scalp hair growth until the middle of the first decade, with severe hair loss by adolescence and complete loss by the third decade. In the family reported by Hess and Uno (1991), scalp hypotrichosis was fully manifest at birth, although it progressed. The same disorder may have been present in the 4-generation family reported by Ibsen et al. (1991). Onset of hypotrichosis was at age 6 to 17 years with almost total scalp alopecia by age 14 to 21 years. No associated ectodermal defects were found.
The CDSN gene (602593), located in the linkage interval on 6p21.3, encodes a protein of 529 amino acids called corneodesmosin that is exclusively expressed in cornified squamous epithelia. Levy-Nissenbaum et al. (2003) found nonsense mutations in CDSN in ... The CDSN gene (602593), located in the linkage interval on 6p21.3, encodes a protein of 529 amino acids called corneodesmosin that is exclusively expressed in cornified squamous epithelia. Levy-Nissenbaum et al. (2003) found nonsense mutations in CDSN in 3 previously reported families: Q215X (602593.0001) in Israeli (Kohn and Metzker, 1987) and Spanish (Betz et al., 2000) families and Q200X (602593.0002) in a Danish family (Betz et al., 2000). Haplotype analysis in the Israeli and Spanish families showed that the mutation arose on a different genetic background in each.