Wooly hair Q84.2

Gossage, 1907

Hair shaft anomaly with diffuse, permanent curling of the hair shaft. It occurs in Caucasians and resembles the hair of African Americans. The diagnosis is made clinically.

In the clinical picture of frizzy hair or "woolly hair", 2 forms are distinguished depending on the occurrence of systemic involvement:

• syndromal frizzy hair (see below RASopathies)
• non-syndromal frizzy hairs.

Non-syndromal "woolly-hair hypotrichosis" is divided into a:

• autosomal recessive (OMIM: 278150/604379/611452)
• and an
• autosomal dominant genotype (OMIM: 194300)

In autosomal recessive curly hair (ARWH/H - OMIM 278150), mutations have been detected in the LIPH- /LPAR6 and KRT25- genes (Mizukami Y et al. 2018). LIPH encodes PA-PLA1alpha - lipase H- an enzyme of the phospholipase family. PA-PLA1alpha is expressed along with its ligand in the inner layer of the hair root sheath. Lipase H produces lysophatidic acid (LPA) an extrezallular mediator of many biological functions that appears to exert growth stimuli on the hair root cells.

The autosomal dominant inherited form (OMIM 194300) occurs at birth or within the first 3 years of life. Associations with trichorrhexis nodosa, pili torti, pili anulati , and trichonodosis have been described. The hair cannot be coiffed. Mutations in KRT71 but also in KRT74, genes coding for keratin 71 and 74, respectively, have been detected in association with woolly hair. Apparently, different genotypes cause a comparable or identical phenotype (Shimomura Y et al. 2010).

Acquired frizzy hair can occur in connection with the use of various medications. Medications. These include: alitretinoin, etretinate, isotretinoin, valproic acid, indinavir, EGFR tyrosinase inhibitors (gefitinib, erlotinib).

Idiopathic hair frizz in healthy adolescents has also been described. Hair frizz is furthermore a phenomenon observed in regrowing hair after cytostatic therapy.

In syndromal frizzy hair a first manifestation is observed in the 1st year of life. With the acquired forms in all stages of life.

Thin, light-colored, finely crimped, not combable hair. The hairs have axial twists of 180 degrees and structurally resemble sheep's wool. The hairs are elliptical or oval with reduced diameter.

An association is found with pili torti, pili anulati and trichonodosis.

Circumscribed crimping hairs are referred to as crimping hair nevus.

CHANDS is the acronym for "Curly Hair Ankyloblepharon Nail Dystrophia". The syndrome is associated with an autosomal recessive homozygous mutation in the RIPK4 gene (605706). RIPK4 is located on chromosome 21q22 (Busa T et al. 2017).

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