Monilethrix in Pattern Distribution in Siblings: Diagnosis by Trichoscopy

Monilethrix is a heritable hair shaft defect characterized by localized or diffuse alopecia resulting from hair fragility over friction areas, predominantly the temporal and occipital regions, and follicular keratosis over the occipital region. However, it lacks macroscopic features that enable easy and rapid diagnosis in medical practice. Hair shaft microscopy is the basis for diagnosing monilethrix. We present a report of two Indian male siblings aged 24 and 21, who presented with thinning and hair loss from the scalp in male pattern distribution and multiple skin-colored follicular papules over the nape of the neck and bilateral forearms since childhood. Trichoscopy of scalp hair revealed characteristic uniform elliptical nodes and intermittent constrictions along with variation in hair shaft diameter, presence of few vellus hair and yellow dots, suggesting a diagnosis of monilethrix with early-onset androgenetic alopecia. Dermoscopy of the papules revealed multiple stubs of broken hair arising from them with a similar beaded appearance, suggesting a diagnosis of monilethrix. The diagnosis of monilethrix was confirmed with light microscopy and hair clipping. This report highlights the patterned distribution of hair loss in monilethrix probably due to the early unmasking of androgenetic alopecia and the use of trichoscopy as the diagnostic modality.