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Paracoccidioidomycosis

With LUIZ FELLIPE DEQUEIROS MATTOSO

Formerly known as South American blastomycosis and still most frequently found in Latin America, the generally accepted terminology is now paracoccidioidomycosis.

Synonyms

South American blastomycosis. Brazilian blastomycosis. Lutz-Splendore-Almeida's disease. Paracoccidioidal granuloma. Para. Ger: Parakokzidioidomykose. Fr: Paracoccidioidomycose. Sp. Paracoccidioidmicosis. Blastomicosis Sudamericana.

Definition

Paracoccidioidomycosis is infection with the thermal dimorphic fungus Paracoccidioides brasiliensis (formerly Blastomyces brasiliensis).

Geographic Distribution

Paracoccidioidomycosis occurs in Brazil and other countries of South and Central America and is the most common systemic mycosis in that region. Where it is endemic, perhaps over 10% of the population has been infected. Only three cases have been reported from the Caribbean, and the infection is rare or nonexistent in French Guiana, Guyana, Belize, Nicaragua, and Surinam. Isolated cases have been reported from the United States, Japan, Europe, and Africa, but each of these patients has lived previously where the infection is endemic.

Epidemiology and Pathology

The ecology and natural habitat of P. brasiliensis are unknown: it is probably a saprophyte in rural surroundings, particularly wet tropical and subtropical regions, and those with dryer, temperate winters. It is difficult to prove this, because the fungus has seldom been isolated from the soil, although the mycelial phase has been grown in the laboratory on various vegetation, dust, and even coffee leaves. The fungus has been found in the testes of a guinea pig following soil inoculation and also from soil with an acid pH in coffee plantations. It has been identified in dog food, but this was probably contaminated. It has been isolated from the gastrointestinal tract of bats and armadillos, but the significance of this is unknown. It may be unique compared with other mycoses in that natural infections occur only in mankind.

Human to human transmission is unknown. Indeed, it is not agreed amongst experts exactly how the infection does occur. A high incidence of lesions in the mouth suggests mucosal infection as the source, but it seems more likely that it is inhaled, because lesions are limited to the lungs in about one-third of patients with the progressive form of the infection. To add further confusion, chest radiographs may be normal even though P. brasiliensis has been isolated from the sputum or bronchial washings of the same patient. It is established that a patient's immunity is to some extent genetic and that the male predominance may be related to an inhibitory effect of estrogen on the in-vivo yeast phase, but whatever the mechanism, the majority of patients with a positive skin reaction have not developed clinical infection.

Paracoccidioidomycosis is common in children of both sexes but the asymptomatic form shows up more frequently over the age of 30 years. In older patients, it is more common in men.

The histopathology (Fig. 6.53) explains the pattern of the infection. When localized, the reaction is mainly granulomatous and the yeasts are inside giant cells. When disseminated, the granulomatous reaction is much less significant, and there is more edema and suppuration, with some localized areas of necrosis and occasional microabscesses. It is unusual to find hyphae. There are more yeast phase cells including extracellular organisms.

In acute paracoccidioidomycosis there are widespread necrotic foci, mainly in lymph nodes, spleen, intestines, bones, and paranasal sinuses. The fungus seems to have a predilection for the lymphoid tissue of the mucosa and the regional lymph nodes. In the small intestine the lesions begin in Peyer's patches, but eventually involve the full thickness of the bowel wall. Lymphadenopathy can be marked and enlarged lymph nodes may coalesce.

When the disease is disseminated, it is the cervical mucosal granulomas on the soft palate have a and mediastinal lymph nodes which are most frequently involved, often becoming caseous. Nodules and there may be painful ulcers in the mouth, makin any organ can also become necrotic. In patients ing eating difficult. Pharyngeal infection may cause with disseminated infections, the adrenals are infected in about half those who come to autopsy, but overt adrenal insufficiency is uncommon.

In the more chronic infections, the skin, lungs, lymph nodes, stomach, small intestine, adrenals, CNS, spleen, and liver are common sites.

In the lungs there may be various tissue reactions, including acute alveolitis, early granulomas, mature granulomas and pulmonary fibrosis. This fibrosis involves also the lymph nodes and bronchi, as well as the major branches of the pulmonary vessels.

In the chronic form of paracoccidioidomycosis, cerebral (CNS) infection may be asymptomatic or, alternatively, the only site with clinical significance. The meninges are involved at the base of the brain and if there is a granulomatous cerebral lesion, it is usually well circumscribed. In the chronic pattern of infection, the thickening of the instestinal mucosa may be such that obstruction may occur in the jejunum, ileum, or colon. Wherever chronic foci occur, as healing progresses they go on to extensive fibrosis.

The diagnosis is made by identifying the fungus in sputum, pus, or other fluids, or in tissue sections. Immunodiffusion tests are useful for diagnosis and screening; immunoelectrophoresis is more sensitive but less practical. Skin tests are unreliable.


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Copyright: Palmer and Reeder