(Due to the ringworm fungus: Tinea trichophytina unguium; Onychomycosis trichophytina. Due to the favus fungus: Tinea favosa unguium; Onychomycosis favosa).
Definition. A condition of one or more nails, due to invasion by the favus or ringworm fungus.
Symptoms. The finger-nails are those usually involved and the invasion is extremely slow, rarely more than one or two being affected. The entire nail is usually invaded although for a long time only a third or a quarter of its surface may appear to be involved. The clinical pictures presented by these two fungi are so similar that the microscope is often necessary to differentiate. The affected nail appears brittle. frayed out, with furrowed surface, opaque, yellowish or grayish-white in color and is lifted up by an accumulation of epidermis underneath it. Other evidences of hypertrophy may appear; the nail becomes thickened, distorted, gryphotic, its surface exfoliated and of a pale dirty color. In these cases due to favus, pin-point- to pin-head-sized sulphur- yellow granulations, peculiar to that disease, are sometimes noted.
Etiology and Pathology. As stated in the definition, the ringworm or favus fungi are the causal factors, contracted as a rule from the eruption of these diseases on the scalp. However, it may develop by auto-infection from any surface of the body. Occasionally, the nails are the principal or sole part involved and, hence, may be the source of contagion to other part or other people. Ordinarily, either fungus can be readily demonstrated by subjecting the scrapings from the affected nail substance to liquor potassae. After softening for several minutes to an hour, the parasite can be seen by a microscopic power of from 400 to 500 diameters.
Diagnosis. The discovery of the fungus microscopically is the only certain test but failure to find it does not exclude its existence. The presence of ringworm or favus elsewhere would indicate the nature of the nail disease. The importance of this may be emphasized when it is remembered that the clinical symptoms of these parasitic affections closely resemble those of psoriasis, eczema and other chronic dermatoses when they affect the nails. Rarely, more than one or several nails are affected by the parasitic diseases, while in the other disease just mentioned, all of the finger, and even the toe-nails, may be involved.
Prognosis and Treatment. Though persistent and stubborn, if the proper treatment is thoroughly carried out, these cases eventually respond. The nails involved must be repeatedly pared, scraped and pumiced. Soaking in an alkaline solution will soften hard and brittle nails or it may be necessary to paint the affected nails with liquor potassae or a stronger potash solution. After the removal of the diseased nail substance, such antiparasiticides as mercuric chlorid, 1 to 3 grains to the ounce, may be applied by dipping the finger ends in the solution for five minutes three times daily, or they may be soaked for the same length of time in a 25 per cent. solution of sodium hyposulphite, after which an ointment of either precipitated sulphur, ammoniated mercury of calomel, 1 dram to the ounce, may be applied continuously until the next soaking. I have used the X-rays successfully in four cases of ringworm and one case of favus of the nails. The treatment is necessarily long continued, with brief exposures and a careful avoidance of pronounced dermatitis. Complete evulsion may be demanded in obstinate cases if the X-rays are not available.