This is a peculiar disease in which nodes appear along the hair shaft, a sort of green stick fracture taking place through these nodes. The latter are black, gray or white transparent swellings, appearing somewhat like the nits of pediculi, causing the hair to feel knotty to the touch, and are usually more pronounced near the distal end. The fracture, when it occurs, may be transverse or longitudinal but always through the nodes. The appearance of the longitudinal incomplete fracture is somewhat like that presented by two brushes being pushed together end to end, while the transverse or complete varieties are brush-like with a frayed appearance, often throughout the length of the hair. The hair itself is usually firmly fixed in the follicle. While the disease usually affects the beard and mustache of men, it can also occur in the axillary and pubic regions of either sex.
Etiology and Pathology. Microorganisms have been found in connection with this disease by Raymond, Hodara and others but the cases presenting a history of direct contagion are very rare. It may be said that, although the real causes are unknown, they are supposedly parasitic while some few are probably trophoneurotic. There is a marked hereditary tendency in some cases. Pathologically, a swelling of the hair shaft which later involves the medulla or body of the hair, leaving the surface skin unaffected, is usually noted. After the fracture occurs, the inner part of the hair degenerates and the medulla is absorbed, while the hair roots may be slightly shrunken or unchanged.
Prognosis and Treatment. Though persistent and rebellious to treatment, efforts to improve the general and local nutrition are usually successful. Shaving or extraction is necessary, followed by antiparasitic lotions or ointments, of which weak mercuric chlorid is the most popular. A case of my own was cured in three months by fractional dose X-raying, applied twice weekly, and the local application of cantharides tincture.