Monilethrix: a clinicopathological illustration of a cortical defect

Abstract

We describe two sisters aged 2 and 7 years, with monilethrix. The older sister was clinically less severely affected but, microscopically, the features of weathering and alternating nodes and internodes were more obvious. The younger girl had more severe alopecia, with shorter hair, but the microscopic features were less marked. Scanning-electron microscopy demonstrated only slight cuticular weathering in both cases, and evidence of breakage in the cuticle at points of no obvious cuticular pathology. Transmission-electron microscopy showed normal cuticle cells in cross-section, but an abnormal cortex. The abnormalities included areas of homogeneous non-fibrillar material, and a deviated axis of some microfibrils. We consider that these findings support the possibility that a cortical defect contributes significantly to the fragility of hair in monilethrix. This might explain why hair with marked beading can be stronger than hair from an affected sibling with less apparent abnormality.

Concomitant Manifestation of Pili Annulati and Alopecia Areata: Coincidental Rather than True Association

“…An additional difficulty in making the diagnosis of PA is that there are few if any complications (2,5). PA has to be differentiated from monilethrix (20,21) and pseudopili annulati. The latter shows similar banding ofthe hair shaft due to periodic twisting and an elliptic shape in cross-section of the hair shaft, but can be excluded by light microscopy (22).…”

Monilethrix

“…Histologically, the follicle shows wide and narrow zones corresponding to the nodes and internodes. [9] Attempts have been made to investigate the mechanism of node formation and to relate it to the diurnal rate of hair growth, but with no overall conclusion. [7,10,11] Intermittent administration of an antimitotic agent can give rise to zones of constriction alternating with zones of normal diameter.…”

Hair Loss in a 6-Month-Old Child

“…1 Associated abnormalities such as juvenile cata¬ racts, syndactyly, nail and teeth abnormalities, and trichorrhexis nodosa have been reported with monilethrix.…”