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Department of Dermatology, KAPV Govt. Medical College, Trichy 620 001, Tamil Nadu
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Narmatha G R, Chithra S, Balasubramanian N. Monilethrix. Indian J Dermatol Venereol Leprol 2002;68:220-221
AbstractMonilethrix is rare hereditary disorder which is in herited as autosomal dominant trit. We report two siblings with a combination of monilethrix and leukonychia.
Monilethrix is characterised by dryness, fragility and sparseness of scalp hair with fusiform spindle shaped swellings of hair shaft separated by narrow atrophic segments and hair breaks at delicate internodes. It was first described by Smith in 1879 as a monosymptomatic disorder. Monilethrix may be associated with keratosis pilaris, leukonychia, koilonychia, dental and opthalmic anomalies, argininosuccinic aciduria. Usually Monilethrix improves by prepubertal age.
We report siblings - boy - 13 year and 10 years respectively born to a consanguineous married parents who came to our O.RD with history of sparse scalp hair and brownish discolouration of hair since birth. Detailed family history was obtained and the pedigree chart showed autosomal dominant type of genetic inheritance. The microscopic examination of hair showed characteristic beading and cracked areas on the thin parts of hair shaft. Additional finding was the presence of leukonychia. Dental defects, sweatgland disorders and mental retardation were excluded in both children. Laboratory examination showed normal blood counts, liver enzymes, serum iorn, copper and zinc in both the boys. [Figure - 1]
The family history revealed hair disorder in two of the counsins. All affected family members noted striking regression during puberty. [Figure - 2]
Monilethrix is generally considered to be an autosomal dominant disorder with variable penetrance. The characteristic beading of the hair is caused by nodes and internodal thinning of the hair shaft with node - internode distance of about 1 mm in a regular pattern. The nodes seemed to represent normal hair growth, with hair medulla & regular number and structure of cortical cells. [Figure - 3]
The internodes in contracts seemed to be more transparent and characterised by a lower number and wrinkling of cortical to be more transparent and characterised by a lower number and wrinkling of cortical cells leading to the fragility of the hair. Histologically there was no hair medulla within these segments. The thin internodes were thought to be the result of diminished anagen hair growth in a 2 day rhythm. In genetic studies, the monilethrix has been mapped to the keratin gene clusters on chromosome 12q 11 -q13 & 17q 12q21. Monilethrix may be defined either as a cortex disease or as a disease of dermal papilla cellcortical cells dysfunction. In some instances, organs of ectodermal origin may be affected by monilethrix.
In conclusion, monilethrix remains as a crucial problem for dermatologists in terms of treatment options. Although monilethrix has been shown to be a structural hair, keratin defect, much of it pathogenesis needs to be elucidated and the search for effective treatment remains.