Monilethrix (Latin – monile = necklace) (syn. beaded hair)
This autosomal dominant hair-shaft defect may be present at birth but un-noted, becoming progressively apparent later with folliculo-regenesis.
It may remain un-presented until beyond adolescence.
In children the hairshafts exhibit swellings or nodes with intervening constrictions. Some hair-shafts may not exhibit the characteristic beaded appearance but remain vulnerable to breakage in the same way.
Hairshafts are fragile and breakage is common at up to 2.5cm. Keratosis (horny follicular papules) may appear at the occiput. Histologically, follicles show zones of varying width corresponding with the nodes and internodes.
The condition frequently occurs in other family members.
X-ray diffraction studies suggest a lowered alpha-keratin concentration.
Electron microscopy has revealed inter-nodal reductions in the number of cortical fibres – thus inducing fragility with the characteristic severance capability.
The condition may disappear after puberty.