CLASS VIII.—PARASITES.
Tinea Favosa.
Tinea Favosa, or favus, is a contagious, vegetable parasitic disease, due to the achorion Schönleinii, characterized by discrete or confluent pea-sized, circular, pale-yellow, friable, cup-shaped crusts, usually perforated by hairs. It is seen commonly upon the scalp, and at times on other hairy regions, involving the hairs and hair-follicles (tinea favosa pilaris), or the non-hairy portions of the integument may be attacked (tinea favosa epidermidis), and cases are occasionally met with in which the nails are the seat of the disease (tinea favosa unguium). The scalp is the usual seat. It begins as a more or less circumscribed, superficial inflammation, with slight scaling, followed by the appearance of one or more yellowish points underneath the superficial epidermis and surrounding hair-shafts. They increase in size, and reach the dimensions of small peas, constituting the so-called favus cups, favi, or favus scutula. They are sulphur-colored, friable, circumscribed, round or oval, with depressed centres, and each pierced with a hair. In their early stage they are bound down to the skin by a layer of epidermis, which surrounds and envelops their periphery. The crusts are elevated from a half to several lines above the surrounding skin, distinctly umbilicated, and if detached an excavated, reddened, atrophied or suppurating surface is disclosed.
The crusts are composed of closely-packed, concentrically-arranged layers, and although they are at first discrete, sooner or later, from increase in number and size, they coalesce, and then their peculiar features are scarcely, if at all, distinguishable, irregular masses of thick, yellowish-white, mortar-like crusts taking their place. If removed, the surface is usually found atrophied, dry or inflamed and moist, and hairless. The hair-shafts are soon involved, the nutrition of these structures impaired, and in consequence the hairs become dry, lustreless, brittle, break off or fall out, and eventually the papillæ are entirely destroyed. Pustules and suppuration are in some instances noted about the borders and beneath the crusts. The pressure of the growing fungus gives rise to atrophy of the skin, which may be seen as depressed, firm, shining, cicatricial-looking areas. The general surface may also be attacked, either together with the scalp or alone. On non-hairy regions, however, the disease is rarely persistent. If the nails are invaded, they become thickened, yellowish, opaque, and brittle. Favus is usually attended with itching, especially when occurring upon the scalp. The odor of the crusts is peculiar, and may be likened to that of mice or stale straw. Upon the scalp the disease is always chronic, if untreated lasting indefinitely.
It is more common in children than in adults, and is seen almost exclusively among the poor. It is comparatively rare in this country. It is contagious. The disease is also encountered in the lower animals, from which doubtless it is not infrequently contracted. The affection is due solely to the growth in the upper layers of the skin of the achorion Schönleinii. This vegetable parasite grows luxuriantly, and constitutes almost entirely the whole mass of the crusts. It can be readily seen by subjecting a small portion of the crust, moistened with diluted liquor potassæ, to microscopical examination, a power of three to five hundred diameters sufficing. It consists of both spores and mycelium. The mycelium is composed of pale-grayish or pale-greenish narrow, flat threads or tubes branching and anastomosing in all directions. The spores are small, variable as to size, round, oval, flask- or dumb-bell-shaped, and are to be seen in abundance in the meshes of the mycelium. Intermediate forms between the spores and mycelium are always present. The hair-follicles and hair-shafts are found to be more or less invaded. If the nails are attacked, the fungus can be easily detected in a section or in scrapings, the mycelium predominating.
As a rule, favus is easily recognized. The small, pale, yellow, friable cup- or saucer-shaped crusts and the peculiar odor are sufficiently characteristic. In some chronic cases, where the crusts are merged into a mass, perhaps mixed with dirt and pus, it resembles pustular eczema; but the condition of the hair, the atrophic patches, and the odor will serve as distinguishing points. Tinea tonsurans can scarcely be confounded with this disease, as it is wanting in the peculiar crust-formation and the tendency to scarring. In doubtful cases the microscope is to be employed.
Favus of the scalp is not only a chronic disease, but is also rebellious to treatment. In neglected cases permanent baldness, atrophy, and scarring sooner or later occur. On the non-hairy portions of the body it is rarely obstinate; involving the nails, it is slow to yield. The first step in the treatment of a case of favus of the scalp, the common seat of the disease, is a removal of the crusts. This is readily accomplished by saturating the parts with simple or carbolized oil, and subsequently washing with soap and hot water. The hair on and around the patches is to be clipped as a preliminary measure; keeping the hair of the entire scalp cut short facilitates treatment, but is not essential. The hairs in the diseased areas are then to be carefully extracted by means of the broad-bladed forceps. This part of the treatment, epilation or extraction of the hairs, is indispensable if the eventual result is to be successful and permanent. Before epilating, the surface to be operated upon is to be anointed with a simple oil. After the operation a parasiticide is to be thoroughly applied, so that it may penetrate the hair-follicles. The whole surface involved is thus treated. Another plan of epilation is that in which the hair is drawn with some force between the thumb and an ordinary tongue-spatula, those that are diseased and loose coming out, while those that are sound remain. In this method the hair is not clipped. The plan is more simple and less tedious than forceps epilation, but is not so satisfactory, as the hairs are more likely to break off, and, moreover, many that are diseased are left unextracted.
Whatever parasiticide is used should be well and thoroughly applied to the affected areas. Those that have the greatest penetrating power are to be selected. Corrosive sublimate, three or four grains to the ounce of alcohol or ether; a 25 per cent. oleate-of-mercury ointment; carbolic acid and glycerin, one part of the former to three or more of the latter,—may be mentioned as among the most useful. Tar, sulphur, and ammoniated mercury and citrine ointments, of officinal strength or weakened; sulphurous acid; a solution of hyposulphite of sodium, a drachm to the ounce,—are also efficient parasiticides. Chrysarobin, in ointment or in chloroform, a drachm to the ounce, has been well spoken of, but must be used cautiously. After several weeks' treatment applications may be suspended for a week or more, so that the condition may again be determined. In ordinary well-developed cases from three to six months' active treatment is required for a removal of the disease.
Favus of the non-hairy portions of the surface requires, after a removal of the crusts, the application of a mild parasiticide, the disease, as a rule, readily yielding. In favus of the nail as much as possible of the affected portion is to be pared or cut away, and a simple parasiticide applied once or twice daily. In those who are debilitated and ill-nourished favus may possibly be rendered less obstinate by suitable internal treatment, with proper nourishment and pure air.