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Fig. 6.55 A-F Pulmonary paracoccidioidomycosis. A Bilateral hilar and mediastinal lymphadenopathy in a young boy. This is a primary infection, which is unlikely to be seen in adults. B Hematogenous "miliary" nodules throughout both lungs. C Multiple small nodules with hilar and mediastinal lymphadenopathy, with some linear streaking due to peribronchial and septal thickening. There is some patchy consolidation in the right lower lobe. D Interstitial thickening particularly in the perihilar regions: there is bilateral lymphadenopathy. E Diffuse interstitial and alveolar consolidation, with fibrosis and some peripheral large nodules. These are mainly in the mid lung field, the lower zones being spared: this is very characteristic of the chronic form of the infection. F Bilateral interstitial fibrosis, with multiple dense nodules and some upper lobe contraction. The lower lobes, particularly the left, have become emphysematous. All these chest radiographs could be misdiagnosed as tuberculosis. (Courtesy of Drs. A. C. Francesconi do Valle and R. R. Guimaras, Rio de Janeiro)

 

 

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Lobomycosis

Lobomycosis is discussed because it is a variety of paracoccidioidomycosis. It was first discovered in 1931 by Jorge Lobo in the Amazon region.

Synonyms

Keloid blastomycosis (queloidiform blastomycosis). Cheloidal (keloidal) blastomycosis. Jorge Lobo's disease. Amazonian blastomycosis. Blastomycoid granuloma. Pseudo leprosy. Fr: Lobomycose. Ger: Lobo Krankheit. Sp: Lobomicosis.

Definition

Lobomycosis is an infection with the fungus Loboa loboi (Paracoccidioides loboi, probably a variation of Paracoccidioides brasiliensis).

Geographic Distribution

Lobomycosis is found in the Amazon valley (with an very high prevalence in Ciaibi Indians), Surinam, and other parts of South and Central America. It has been recognized in France.

Epidemiology and Pathology

Lobomycosis is most common in thickly vegetated tropical climates. More than 300 cases have been confirmed in humans. There is no racial preference, but depending on the pattern of work, men in some areas and women in other areas are more affected. The infection occurs in humans and dolphins, but the fungus has not yet been cultured. The mode of entry is presumed to be through skin abrasions, particularly in agriculture workers. Most patients are therefore rural inhabitants or living in jungles. The clinical course is so slowly progressive that patients seldom remember when or how it started. Transmission from human to human has not occurred, though transmission from human to dolphin has been observed (the incubation period was 3 months).

The infection causes subepidermal nodules which histopathologically are granulomas with multiple hyaline fibers, histiocytes, and giant cells (Fig. 6.60). There is very little inflammatory reaction or suppuration.

The diagnosis is made by clinical observation of the characteristic skin lesions, or by finding the fungus on tissue sections (Fig. 6.60 G). So far, skins tests and serology are not available. This is important, because as there is no specific treatment, the best hope of cure is early excision.

Clinical Characteristics

There are no systemic symptoms. Patients present with freely mobile subepidermal nodules which may coalesce to form large masses, covered by thinly stretched overlying epidermis. They closely resemble hard shiny keloids and cause little discomfort (see Fig.6.1 A, Fig.6.60 A). They can be hyperesthetic or anesthetic. Mucosa and internal organs are not involved. Eventually, some of the nodules may fungate or ulcerate and sometimes spread to lymphatics. They seldom heal spontaneously: squamous cell carcinoma has developed in chronic lesions. Remote elevated crusted plaques are probably caused by auto-inoculation.

Imaging Diagnosis

There are no imaging findings of significance. Lobomycosis is included because it is often discussed in reference to blastomycosis and radiologists must be aware that there is such an infection and, if asked, that there is no reason for imaging because spread beyond the obvious lesion is not known to occur.

 

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