Marie Unna hereditary hypotrichosis

ARTICLE

Hypotrichosis of the Marie Unna variety is a distinctive disorder named after a publication in 1925 describing a German family in which 27 individuals over seven generations were affected by a previously unreported type of congenital hypotrichosis [1]. Its inheritance is determined by an autosomal dominant gene and usually occurs as an isolated defect.

We have recently had the opportunity to study a member of an Italian family in which 20 kindred over six generations were affected by Marie Unna hereditary congenital hypotrichosis, and we describe here the clinical, ultrastructural, and histopathologic findings of this case, as well as a new family pedigree.

Case report

The proband patient was a 32-year-old man who had widespread scalp alopecia with short and sparse hair and low traction resistance (Fig. 1). The hair itself was very coarse to the touch, similar to a horse's tail, and was deeply pigmented. Eyebrows and lashes had been absent from birth, whereas progressive alopecia affected all body hair with increasing age. Particularly during adolescence, the hair became more sparse on the scalp and formed a peculiar pattern resembling that of male-pattern alopecia on the vertex and frontal areas, but the perimeter of the scalp was also bald. Subsequently, the hair density decreased throughout the entire scalp producing the clinical appearance of a cicatricial alopecia (pseudopelade of Brocq). General body hair was absent (trunk and limbs) and only sparse axillary, pubic, and beard hair was observed.

Ligh microscopy of the abnormal hair revealed characteristic torsions of the hair shaft, which were more clearly detectable with scanning electron microscopy. Ultrastructurally, the hair shafts appeared flattened, with longitudinal grooving, and were twisted 360 degrees along their main axis (Fig. 2).

The histopatologic examination of a 4 mm punch biopsy taken from the scalp showed a marked reduction of the hair follicles. Focal inflammatory infiltrate and an increased number of fibroblasts were seen adjacent to the remaining follicles.

Teeth, mucous membrane and nails, as well as the general physical and mental development were normal, excluding the possibility of an ectodermal syndrome.

Careful evaluation of the family history (pedigree, Fig. 3) revealed 20 kindred over six generations to various degrees affected by the same hair abnormalities, suggesting an autosomal dominant mode of inheritance of this disorder. All the affected relatives had coarse hair and no eyebrows and lashes. The majority of them had scalp alopecia and little body hair.

Discussion

Hair abnormalities are commonly observed in a variety of hereditary syndromes which include associated defects of ectodermal or mesodermal origin [2]. Diffuse hereditary hair defects as isolated phenomena are rare, but hereditary hypotrichosis is in example of such a disorder. This was first extensively described by Marie Unna in a large German kindred whose descendants were later studied by other authors [3-5]. Other affected families were reported in Germany [6,7], Hungary [8], Yugoslavia [9, 10], France [11], UK [12, 13], United States [14] and Italy [15, 16]. Our patient (a southern Italian) showed the typical features of this disorder, namely, a distinctive structural defect of the hair shaft, generalized hair loss, and an autosomal dominant pattern of inheritance.

The ultrastructural hair findings consist of both torsion and longitudinal grooving of the hair shaft [17]. This pilar dysplasia seems to be a characteristic finding of a "community" of ectodermal dysplasias in which there are other features such as variable midfacial malformations and limb defects [18]. In Marie Unna hereditary congenital hypotrichosis this hair shaft abnormality is observed as an isolated defect. Some recent reports signaled the association of Marie Unna hypotrichosis with other diseases such as Ehlers-Danlos syndrome [19] and juvenile macular degeneration [11, 13] which could be considered as incidental findings.

Several mechanisms can be involved in the genesis of the typical hypotrichosis affecting patients with Marie Unna's syndrome: firstly, due to the abnormal hair shafts, the hair becomes fragile and is easily broken at the twisted points [18]; secondly, this coarse hair is gradually lost as follicles are progressively destroyed by a scarring process [20] or become gradually smaller and involute with no evident inflammatory changes [16]; thirdly, because lashes and eyebrows can be absent from birth, a primary loss of hair follicles can also be speculated.

Due to the heterogenity of the "uncombable" hair symptom, it is important to look for associated abnormalities, carry out pedigree analyses, and perform scanning electron microscopic studies of the hair in order to make an exact diagnosis.

REFERENCES

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