Marie Unna Hereditary Hypotrichosis
Marie Unna hereditary hypotrichosis (MUHH) is a very rare autosomal dominant form of inherited hair loss, first described by the dermatologist Marie Unna in 1925.
It is marked by a distinctive three-stage change in the hair:
- At birth: The baby is born completely bald (atrichia) or with only a little fine, thin hair.
- Childhood: Hair starts to grow back, but it is abnormal: rough, stiff and irregularly wavy, like wire (coarse, wiry hair).
- Puberty and adulthood: Widespread, irreversible hair loss sets in and progresses to balding at the crown and temples.
At the molecular level, MUHH stems from loss of translational control over the hairless (HR) gene:
- U2HR (upstream open reading frame) mutations: The disease is caused by point mutations in U2HR, a short upstream open reading frame in exon 2 of the HR gene.
- Overproduction of hairless protein (HR overexpression): Normally, the short peptide encoded by U2HR acts as a brake (translational repressor) that stops the HR gene from being over-translated. When U2HR is mutated, the brake fails and hair follicle progenitor cells make far too much hairless (HR) protein.
- Disrupted Wnt/beta-catenin signaling: Excess HR protein is a strong transcriptional repressor that shuts down the Wnt signaling needed to sustain anagen. As a result, follicles are pushed early into the regression phase (catagen), gradually shrink (miniaturization) and lose the ability to produce new hair.
In adults, MUHH is easily mistaken for androgenetic alopecia (AGA) or alopecia areata. At Haute-Derma, a dominant family history (several generations affected) together with a history of "wiry hair in childhood" are the two most important clinical clues that point us to MUHH.
Clinical Features and Trichoscopy Findings
MUHH follows a clear course that tracks the body's developmental milestones:
- Clinical Features at Each Stage:
- Newborn: The baby has no hair at all or only a few fine wisps. Eyebrows and eyelashes are often sparse or absent.
- Childhood (from age 2–3 until puberty): Hair grows in abnormally. It is coarse, stiff and rough, lacks natural shine and feels prickly, like wire, to the touch.
- After puberty: Hair begins to thin from the crown (vertex) and temples, progressing to extensive balding similar to male-pattern hair loss.
- Trichoscopy and Microscopy:
- Wiry hair: The shaft varies in diameter and shows slight twists around its axis, but without the regular 180-degree twisting seen in pili torti.
- Markedly reduced follicle density: The number of active follicular openings falls over time.
- Follicular miniaturization: Miniaturized, vellus-like hairs are seen interspersed with yellow dots, which represent empty follicular openings filled with sebum.
Clinical Management and Care at Haute-Derma
Because MUHH is caused by a mutation in a regulatory element (U2HR), there is currently no treatment that can correct the underlying genetic defect. Care focuses on slowing hair loss and providing psychological support:
Slowing Follicle Shrinkage and Preserving Density
- Topical minoxidil solution: Minoxidil prolongs anagen in follicles that have not yet fully miniaturized, helping maintain hair density for as long as possible before balding sets in.
- Nutritional supplements: Biotin, zinc and sulfur-containing amino acids (L-cystine) are prescribed to improve the resilience of the hair shaft during the coarse-hair stage.
Protecting Hair From External Damage
- Gentle care: Avoid rough brushing or pulling hard on stiff, wiry hair.
- Limit chemical and heat treatments: Avoid perming, dyeing, bleaching and flat irons, because the keratin cortex of MUHH hair is very vulnerable to heat and chemical damage.
Genetic and Cosmetic Counseling
- Genetic counseling: Because MUHH is autosomal dominant, an affected person has a 50% chance of passing it on with each pregnancy. Sequencing the U2HR region clarifies the inherited risk for the next generation.
- Cosmetic options: Once balding progresses after puberty, high-quality medical hair systems or hair weaving are the best options to help patients feel confident in daily life.
