Last Updated: 2023-07-07

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

ICD11: EC21.0

Smith 1879

Aplasia pilorum moniliformis, Aplasia pilorum intermittens, Aplasia moniliformis, spindle hairs, beaded hairs

Hereditary hair growth disorder with increased fragility.

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


Mostly inconspicuous hair at birth. In the first months of life, fragile, brittle hairs with regular flare-ups (knots) appear. In some cases, the hair may break off very close to the hair root that a “pseudoalopecia” occurs.

Possible associations:

  • Keratosis pilaris
  • Coilonychia

Trichogram (regular distension (nodi) are pathognomic).

In a few cases, hair will grow 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 .