Last Updated: 2019-08-27

Author(s): Anzengruber F., Navarini A.

ICD11: -

Smith 1879

Aplasia pilorum moniliformis, Aplasia pilorum intermittens, Aplasia moniliformis, spindle hairs, pearled hairs

Hereditary hair growth disorder with increased fragility.

  • Point mutations, mostly with autosomal dominant inheritance, in a few cases also AR described.
  • High penetrance.
  • Variable expressivity.
  • Probably caused by alternations of hair cortex keratins 1 and 6.


Usually inconspicuous hair at birth. In the first months of life, fragile, brittle hair with regular tufts (knots) occurs. In some cases, the hair can break off very close to the hair root, leading to "pseudoalopecia".

Possible associations:

  • Keratosis pilaris 
  • koilonychia

Trichogram (regular distensions (nodi) are pathognomic).

In a few cases, hair grows again in the course of life.

  1. Nedoszytko B, Lewicka-Potocka Z, Szczerkowska-Dobosz A, Gleń J, Bykowska B, Świątecka-Czaj J, Nowicki R. Monilethrix in monozygotic twins with very rare mutation in KRT 86 gene. J Eur Acad Dermatol Venereol. 2017 Mar 16. 
  2. Shah K, Ansar M, Mughal ZU, Khan FS, Ahmad W, Ferrara TM, Spritz RA. Recessive progressive symmetric erythrokeratoderma results from a homozygous loss-of-function mutation of <i>KRT83</i> and is allelic with dominant monilethrix. J Med Genet. 2017 Mar;54(3):186-189. doi: 10.1136/jmedgenet-2016-104107 .