Mycetoma

Considering the many people who walk barefoot, it is surpising that the saprophytes of the soil so seldom infect the feet. But this does happen occasionally, notably in the Sahel area of Africa, and in parts of South India, Mexico, Brazil, and the Middle East, each area having its own particular species. If a peasant in one of these areas treads on an acacia thorn, or some other sharp object, it may may infect him with filamentous fungus-like bacteria (Streptomyces, Actinomyces,or Nocardia), or the true fungi (the eumycetes, particularly Madurella). These cause a chronic granulomatous swelling, with multiple sinuses that discharge characteristic granules, each of which has arisen in a micro-abscess. The lesion is usually in a patient's foot, but his leg, finger, hand, thigh, trunk, jaw, or head may also be affected, and may be difficult to diagnose.

He is usually a farmer who has a painless swelling on his foot at the site of a thorn prick some months earlier. This grows slowly to form a circumscribed, rubbery or cystic, lobulated mass. If it is on his sole, pressure flattens it into a disc. Sinuses appear, and occasionally discharge granules. As one sinus heals more appear, and become secondarily infected, but this secondary infection does not extend deeply. By the time that five years have elapsed, his whole foot is swollen, and covered with open sinuses and the scars of healed ones. It is still painless, and as he has no systemic symptoms he continues to work. As his foot disintegrates, he takes to a crutch. Spread to his lymph nodes is late and uncommon, and only after about ten years do sinuses start to form in the nodes of his groin.

The primary site of infection is usually in his subcutaneous fat, but it may be in fat which is deep to fascial planes. These form a natural barrier to the spread of infection, so that if it gets under his plantar, or palmar fascia, it may spread between his tendons, along his lumbrical canals, and even through his carpal tunnel, up into his forearm. His bone may be invaded relatively early, still without causing him pain.

Mycetomas never regress spontaneously. Chemotherapy has no effect on the true fungus Madurella, but it is worth trying a long period of dapsone, trimethoprim, and streptomycin on Streptomyces and Nocardia, and trying penicillin on Actinomyces, as described below. Ketoconazole 200 mg once or twice daily with meals (expensive) has also been used. The ultimate treatment is amputation, but perhaps only after 20 years, if necessary accompanied by clearance of the regional nodes. The vascularity of a limb is not impaired, so that you can amputate at a site of election, provided it is through healthy tissue (56.1).

Fig. 31-2 MYCETOMA. A, mycetoma of the hand, spreading through the carpal tunnel into the forearm (unusual). B, an advanced mycetoma of the thigh 20 years after infection had begun in the foot. C, the endemic and the sporadic mycetoma zones in Africa. D, early black grain mycetomas of the soles of both feet, showing flattened disc-shaped swellings. This is the typical early lesion, but the simultaneous involvement of both feet is unusual. E, a more advanced lesion. F, a mycetoma of the dorsum of the foot. This may be part of a dumb-bell lesion extending from the sole between the metatarsals. G, a diffuse mycetoma of 10 years' duration; it is still painless and its owner is still working. After Crockett DJ, ''Mycetoma', Figs. 1 to 8. ''Tropical Doctor' Vol.3:No. 1, with kind permission. Crockett, DJ. ''Mycetoma' Tropical Doctor 1973;3:28[nd]33.

MYCETOMA DIAGNOSIS. Try to find the granules, because without them all a pathologist can say is that there is a granulomatous infection with multiple micro-abscesses.

In the endemic zone in Fig. 31-2.

Streptomyces somaliensis forms yellowish-white medium sized, 0.5 to 1 mm, soft, round, smooth granules.

Madurella mycetomi and [f36]Leptosphaeria senegalensis, form brown or black, large, 1 to 3 mm, irregular, fissured, aggregated, hard, brittle granules.

Streptomyces pelletieri forms red, minute, 0.3 mm, faceted, aggregated, very hard granules.

[+5]In the sporadic zone.

Nocardia brasiliensis forms yellowish, minute 0.3 mm, irregular, lobulated, soft granules.

Streptomyces madurae forms white, yellow or pink tinged, large, 1 to 3 mm, soft, lobulated granules.

X-RAYS. Once a patient's periosteum is breached, his tarsal and metatarsal bones are rapidly destroyed. New bone in the walls of abscesses forms buttresses projecting outwards at angles to the shaft of a long bone. The centre of an infected bone has a honeycomb appearance, and a good film shows tiny cystic areas of bone destruction, each the site of a micro- abscess.

CHEMOTHERAPY [s7]FOR MYCETOMA If you find the granules of Nocardia brasiliensis, try prolonged continuous treatment with dapsone 100 mg twice daily for 2 years or more. Streptomycin 1 g daily by intramuscular injection is also effective. Treatment is so protracted, and the disease so painless, that he is unlikely to co-operate for long. You may be wise to reserve dapsone for lesions of the posterior part of his foot, or in his hand, for which the only alternative is a high amputation.

If you find the granules of Streptomyces somaliensis, try trimethoprim 100 mg, twice a day for many months, or even a year or more.

If you diagnose actinomycosis, caused by such organisms as Actinomyces israeli, try penicillin for 2 or 3 months.

CAUTION ! With long-continued treatment, watch carefully for side-effects. Dapsone: neuropathy, allergic dermatitis, anorexia, nausea and vomiting, headache, insomnia, hepatitis, agranulocytosis (all rare). Trimethoprim: vomiting, rashes, erythema multiforme, epidermal necrolysis, eosinophilia, agranulocytosis, granulopenia, purpura, leucopenia; megaloblastic anaemia. Streptomycin: tinnitus, vertigo and deafness, a widespread fine rash, drug fever, nephrotoxicity (rare), and paraesthesiae of the mouth (very rare).

With all other mycetomas, the only treatment is symptomatic. Short courses of tetracyclines will control secondary infection in the sinuses, and encourage them to heal, but will not eradicate the disease. Curette and drain any low-grade abscesses that form.

SURGERY [s7]FOR MYCETOMA If a lesion is localized, and is confined to a patient's soft tissues, excise it and repair the defect with a split skin graft.

If he has a lesion of his forefoot which involves bone, or which will expose bone on a weight-bearing surface if you remove it, Syme's amputation may be appropriate (56.9).

If he has a lesion of his hindfoot with minor bone involvement, and without severe disorganization of its joints, treatment depends on the organism: (1) If it is Nocardia, as determined by the district he comes from and Fig. 31-2, give him dapsone, and drain the lesions if necessary, but don't amputate. (2) If any other organism is responsible, you will probably have to amputate, but wait until his foot becomes a real nuisance.

If he has a lesion of his hind foot with severe bone and joint destruction, do a below-knee amputation (56.8).

CAUTION ! (1) Mycetoma is painless, so don't amputate a limb until he is quite sure that his limb is of no use. (2) Observe him carefully, and make sure he reports any involvement of his inguinal nodes. If he does, amputate immediately, and clear them by block dissection (32.34).

Mr Printer. Please take in the ''not in series' figure ''The patient exhibited marked oedema' somewhere where there is a gap in Sections 31.4 to 31.7, probably here.