Monilethrix: beaded, fragile hair explained

The name comes from the Latin word for necklace (monile) and the Greek word for hair (thrix). MedlinePlus Genetics explains that under a microscope the hair shaft shows regular narrowings, so that each strand looks like a string of beads. People with monilethrix have sparse hair growth (hypotrichosis) and short, brittle hair that breaks easily.

The beading itself is not visible to the naked eye. What people notice is that the hair is short, thin, fragile or patchy, and that it breaks readily at the points where the shaft narrows. A 2021 case report describes the wide, nodular parts of the shaft as having normal thickness and containing the medulla, with the narrow internodal parts being the abnormal segments, where fractures occur.

No UK patient leaflet on monilethrix was available when this page was prepared. The information here draws on MedlinePlus Genetics and published case reports, and a dermatologist is the right source for personal advice.

MedlinePlus says affected individuals usually have normal hair at birth, but abnormalities develop within the first few months. In mild cases only the hair on the back of the head (occiput) or nape of the neck is affected. In more severe cases the whole scalp can be affected, together with pubic hair, underarm hair, eyebrows, eyelashes or hair on the arms and legs.

A published report of two brothers describes alopecia that is more severe in areas prone to friction, with the temporal and occipital regions most affected, together with small bumps called follicular keratosis over the nape of the neck and forearms. MedlinePlus similarly notes that some people have keratosis pilaris, and that some have abnormal fingernails or toenails.

A 2021 report of a family of six affected members across two generations emphasises how variable the condition is: the range runs from an almost normal scalp with few changes to total alopecia, and milder forms can go unnoticed. It also notes that there was no clear correlation between the specific genetic change and severity, suggesting that other factors may influence expression.

MedlinePlus says monilethrix is caused by mutations in one of several genes. Mutations in KRT81, KRT83, KRT86 or DSG4 account for most cases. The first three provide instructions for hair keratins, tough fibrous proteins that give hair its strength and elasticity, while DSG4 makes a protein found in desmosomes, structures that help attach cells to one another. Some people with monilethrix do not have a mutation in any of these genes, and in some the cause is unknown.

Inheritance can follow several patterns. When a keratin gene is involved the condition is inherited in an autosomal dominant pattern, meaning one altered copy of the gene is enough. In rare cases it results from a new mutation. When DSG4 is involved it is autosomal recessive. A clinical genetics service can explain which pattern applies to a family.

Case reports describe hair shaft microscopy as the basis of diagnosis. Trichoscopy, which is dermoscopy of the scalp, can show uniform elliptical nodes separated by intermittent constrictions, with hair shafts that bend regularly and often appear broken. In the report of the two brothers, the diagnosis was confirmed with light microscopy of clipped hair.

Because monilethrix can mimic ordinary hair loss, it may be mistaken for other conditions. The same report describes a patient in whom early male-pattern hair loss coexisted with monilethrix. A dermatologist will take a history, ask about family members, examine the scalp and hair, and may take a few hairs for microscopy.

A 2021 case report states that there is no definitive treatment for monilethrix, and notes that case reports have shown improvement with topical use of 2 per cent minoxidil and with systemic agents such as biotin, N-acetyl cysteine, corticosteroids, acitretin, oral contraceptives and griseofulvin. These are individual reports rather than trials, so they should be discussed with a dermatologist and not treated as proven.

Because the hair breaks at points of friction, gentle handling is the general principle: avoiding tight styling, traction and heat, and protecting areas that rub, such as the back of the head against pillows or collars. These are general measures that follow from the fragility of the shaft rather than recommendations drawn from the sources.

Many people also find the emotional impact of hair loss significant, particularly in childhood and adolescence. A GP can refer to dermatology and, where appropriate, to psychological support.

MedlinePlus describes monilethrix as a condition that affects hair growth, with only occasional skin and nail involvement. Severity differs from person to person, even within one family, and some people have only minor patches. Genetic counselling is available for families who want to understand recurrence risk.