Monilethrix is a hair shaft disorder characterized by nodes along the hair shaft. The elliptical nodes occur at regular intervals and are connected by nonmedullated tapered constrictions (internodes). Internodal fragility leads to hair breakage and alopecia that can be dramatic. The extent of involvement can vary widely; monilethrix most commonly affects the nape of the neck and occiput but may involve the entire scalp as well as facial and body hair. Inheritance can be autosomal dominant (due to a keratin 81, 83, or 86 mutation) or autosomal recessive (due to a desmoglein 4 mutation). 

Monilethrix usually occurs in early childhood but can occur after puberty. Affected individuals are usually born with normal hair, which is replaced with short, fragile, brittle hair in the first months of life.