Marie Unna Hereditary Hypotrichosis

A rare autosomal dominant hair loss disorder characterized by the absence or scarcity of scalp hair, eyebrows, and eyelashes at birth; coarse and wiry hair during childhood; and progressive hair loss beginning around puberty.

Epidemiology

Prevalence and incidence are unknown.

Clinical description

Affected individuals of both sexes are typically born with an absence or scarcity of scalp hair, eyelashes, and eyebrows. During early childhood the scalp hair becomes coarse and wiry. Loss of scalp hair begins around puberty in a pattern resembling that of androgenetic alopecia and progresses to almost total alopecia. Body, axillary, and pubic hair is sparse or absent as is beard hair in men and adolescent boys. No other ectodermal abnormalities are observed.

Etiology

MUHH is due to mutations in U2HR, an inhibitory upstream open reading frame of the HR gene located to 8p21.2, causing a gain of function of HR. Worldwide, more than 15 different U2HR mutations have been identified in nearly 30 affected families and sporadic cases. Recently, a missense mutation in EPS8L3, located on chromosome 1p13.2, was identified in a Chinese family with MUHH.

Diagnostic methods

Diagnosis depends on clinical and microscopic examination and can be confirmed by mutational analysis of U2HR. Scanning electron microscopic study of the hair reveals irregular twisting, longitudinal ridging and cuticle peeling. Scalp biopsy shows a marked reduction in the number of follicles with follicular fibrosis. However, the small number of biopsies analyzed makes it difficult to obtain an objective impression.

Differential diagnosis

Differential diagnoses include hypotrichosis simplex, loose anagen syndrome, uncombable hair syndrome, ectodermal dysplasia syndromes (see these terms), congenital atrichia, androgenetic alopecia and alopecia areata.

Antenatal diagnosis

Antenatal diagnosis can be performed but is the exception, as MUHH is not a life-threatening disease. Therefore in practice, this is handled in quite a restrictive manner.

Genetic counseling

There is a 50% recurrence risk for offspring of affected individuals as transmission is autosomal dominant.

Management and treatment

No curative treatment exists for MUHH.

Prognosis

Life expectancy is normal but quality of life can be reduced due to the psychological impact related to the hair phenotype.