Monilethrix is a rare genetic disorder of the hair; it is one of the keratin disorders. Hair keratins have two forms, one acidic and one basic; in monilethrix, one or both of the keratin genes have mutated. The effect of the disorder on the individual’s hair is variable. In most cases the hair is thin and brittle. The hair shaft is sufficiently fragile that the hair breaks before it is able to get very long. The affected hair may be confined to one region of the head, or it may not be localized. Even within a localized, affected section of the head, not all hairs may be affected. The area around the hair follicles may be enlarged or covered with scales. Because keratin is also involved with fingernails and toenails, these may be affected as well. Finally, monilethrix may combine with other ectodermal disorders.
A genetic defect of the hair shaft in which the hair becomes beaded and brittle. The defect usually appears by the second month of life. There is no effective treatment.