Rubromycosis, or Rubrophytia

Etiology. Epidemiology. The anthropophilic fungus T. purpureum is highly contagious. Rubromycosis accounts for 60-70 to 90 per cent of all cases with mycosis of the feet, while the incidence of its generalized forms is 15 to 20 per cent and more that of rubromycosis of the feet and hands. It is believed that the routes of infection and spread are the same as those in epidermophytosis. The high epidemiological significance of rubromycosis is associated with the infection being probably transmitted through towels, gloves, mittens, and through hand shaking. The disease prevails in adults, though reports of rubromycosis among children have been growing lately.

Pathogenesis. A considerable role in the development of the disease is attached to increased dryness of the skin, hyperkeratosis, and diminished resistance of the horny layer keratin and downy hair. Abnormalities in the function of the endocrine glands and various neurovegetative dysfunctions are often encountered in patients with rubromycosis. There are indications that antibiotics, cytostatic agents, and corticosteroids used in the treatment of other diseases play a definite role in the pathogenesis of rubromycosis.

Clinical picture and course. There are several clinical varieties of the disease: rubromycosis of the feet, rubromycosis of the feet and hands, generalized rubromycosis, and rubromycosis of the nail plates.

Rubromycosis of the Feet

The foot is the most common localization of the disease. The lesions appear first in the interdigital folds all of which, or almost all, are involved (as distinct from epidermophytosis). The process then extends to the skin on the soles which becomes infiltrated, dry, and diffusely hyperemic, the skin furrows are clearly seen and are marked by furfuraceous scaling. The process also spreads to the sides and dorsal surfaces of the feet and toes. Affection of the skin on the feet leads sooner or later to involvement of the nail plates in the process as a rule. In other cases, the process begins with affection of the nail plates and then spreads to the skin on the feet.

Rubromycosis of the Feet and Hands

The disease first appears on the skin of the feet and only later the hands and the finger nails become involved. Initial penetration of the skin on the hands by the fungus is less frequent. The clinical picture of the disease is almost similar to that in affection of the skin on the feet, but is less in intensity (because the hands are washed repeatedly). There is an interrupted swelling on the periphery of the foci, which is often found also on the back of the hands.

Rubromycosis of the Nail Plates

The disease is often encountered. In some cases it is an isolated affection of the nails, in others it is combined with affection of the skin on the feet and hands or with generalized rubromycosis. Involvement of many nail plates in the process is a characteristic feature, quite often all the finger and toe nails are affected. In the normotrophic type of rubromycotic onychia, the thickness of the nail plate remains normal; the lesion occurs on the free edge or the sides of the nail as white or yellowish bands; similar bands may show through the thickness of the nail plate. The hypertrophic type of the disease is marked by thickening of the nail plate, which crumbles and breaks easily, and by subunguinal hyperkeratosis; the above-mentioned bands may also be encountered. In the atrophic type of onychia, the nail plate is thinned out, its greater part is destroyed and only the part next to the nail wall remains. Sometimes the nail plate is separated from the nail bed as in onycholysis.

The diagnosis in typical affection of the feet, hands, and nail plates is not difficult, the more so since it is easily verified by microscopy of the pathological material.

Rubromycosis of the skin on the feet and interdigital folds without involvement of the skin on the hands and the nail plates has to be differentiated with intertriginous and squamous forms of tinea pedis the clinical picture of which may be similar in essence. The diseases of the nail plates listed above are, naturally, attended with the corresponding changes on other skin areas and the mucous membranes, which makes the diagnosis of onychia much easier.

The final decision concerning the disease may be made on the basis of cultural diagnosis, i.e. growth of the culture of the fungus, the causative agent of the disease, on nutrient media (usually Sabouraud's medium).