It may occur at any age, but is most common between thirty and thirty-five. It has been reported in utero by Guyot, and was seen to extend up to the thigh, a statement that is most likely fallacious. However, there are well- authenticated cases in infants, and again in persons over seventy years of age.
In some few cases the metatarso-phalangeal joint is affected; but no case has been seen at the base of the ungual phalanx. The duration of the disease is between two and four years, but Dr.
Evans's case had been in progress fifty years. It rarely runs its full course before a year.
Ainhum begins as a small furrow or crack, such as soldiers often experience, at the digito-plantar fold, seen first on the inner side. This process of furrowing never advances in soldiers, and has been given a name more expressive than elegant. In ainhum the toe will swell in a few days, and a pain, burning or shooting in nature, may be experienced in the foot and leg affected. Pain, however, is not constant. There may be an erythematous eruption accompanying the swelling. The furrow increases laterally and in depth, and meets on the dorsal aspect of the toe, giving the toe the appearance of being constricted by a piece of fine cord. As the furrow deepens the distal end of the toe becomes ovoid, and soon an appearance as of a marble attached to the toe by a fibrous pedicle presents itself. By this time the swelling, if any, has subsided. The distal end of the toe bends under the foot, and becomes twisted when walking, and causes inconvenience, and, unfortunately, says Eyles, it is in this last stage only that the Fanti presents himself. There is in the majority of cases a small ulcer in or near the digito-plantar fold, which causes most of the pain, particularly when pressed upon. This ulcer does not occur early, and is not constant. The case under Pyle's observation showed no ulceration, and was absolutely painless, the negress applying for diagnosis rather than treatment. The furrow deepens until spontaneous amputation takes place, which rarely occurs, the patient generally hastening the process by his own operation, or by seeking surgical treatment. Adry scab forms at the furrow, and when picked and repicked constantly re-forms, being composed of horny desquamation or necrosis.
The histology of ainhum shows it to be a direct ingrowth of epithelium, with a corresponding depression of surface due to a rapid hyperplasia that pushes down and strangles the papillae, thus cutting off the blood supply from the epithelial cells, causing them to undergo a horny change.
The disease is not usually symmetric, as formerly stated, nor is it simultaneous in different toes. There are no associated constitutional symptoms, no tendency to similar morbid changes in other parts, and no infiltration elsewhere. There is little or no edema with ainhum. In ainhum there is, first, simple hypertrophy, then active hyperplasia The papillae degenerate when deprived of blood supply, and become horny. Meanwhile the pressure thus exerted on the nervi vasorum sets up vascular changes which bring about epithelial changes in more distant areas, the process advancing anteriorly, that is, in the direction of the arteries.
This makes the cause, according to Eyles, an inflammatory and trophic phenomenon due mainly to changes following pressure on the vasomotor nerves.
Etiology.--The theories of the causation of ainhum are quite numerous. The first cause is the admirable location for a furrow in the digito-plantar fold, and the excellent situation of the furrow for the entrance of sand or other particles to make the irritation constant, thus causing chronic inflammatory changes, which are followed subsequently by the changes peculiar to ainhum. The cause has been ascribed to the practice of wearing rings on the toes; but von Winckler says that in his locality (British Guinea) this practice is confined to the coolie women, and in not one of his 20 cases had a ring been previously worn on the toe; in fact all of the patients were males. Digby says, however, that the Krumens, among whom the disease is common, have long worn brass or copper rings on the fifth toe. Again the natives of India, who are among those most frequently afflicted, have no such custom.
Injury, such as stone-bruise, has been attributed as the initial cause, and well-authenticated cases have been reported in which traumatism is distinctly remembered; but Smyth, Weber, and several other observers deny that habits, accidents, or work, are a feature in causation.
Von During reports a curious case which he calls sclerodactylia annularis ainhumoides. The patient was a boy about twelve years old, born in Erzeroum, brought for treatment for scabies, and not for the affection about to be described. A very defective history led to the belief that a similar affection had not been observed in the family. When he was six years old it began on the terminal phalanges of the middle fingers. A myxomatous swelling attacked the phalanges and effected a complete absorption of the terminal phalanx. It did not advance as far as gangrene or exfoliation of bone. At the time of report the whole ten fingers were involved;the bones seemed to be thickened, the soft parts being indurated or sclerosed. In the right index finger a completely sclerosed ring passed around the middle phalanx. The nails on the absorbed phalanges had become small and considerably thickened plates. No analogous changes were found elsewhere, and sensation was perfectly normal in the affected parts. There were no signs whatever of a multiple neuritis nor of a leprous condition.
