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Fig. 6.53 A, B. The histopathology of paracoccidiodiomycosis. A Rounded fungi with peripheral budding, giving a "ship's wheel" appearance which is typical of P brasiliensis with a surrounding inflammatory infiltrate. H & E, x100. B Binary and peripheral budding, again with the "ship's wheel" outline. The multiple buds which give the nodular "ship's wheel" appearance are very characteristic. Grocott-Gomori methenamine-silver stain, x400. (Courtesy of Dr. I. L. Aymor, CLAP, Rio de Janeiro)


Fig. 6.54 A-F. The clinical appearance of paracoccidioidomycosis. A Subacute disseminated infection with multiple small ulcerating nodules on the face and neck, and associated cervical lymphadenopathy. B Multiple small ulcerating lesions around the face and a mucocutaneous, more extensive lesion on the upper lip. C An ulcerating granulomatous lesion near the elbow with multiple small nodules around it. D A mucocutaneous lesion across the upper lip. E A large solitary ulcerating lesion on the side of the tongue. F Multiple small ulcerating lesions under the tongue. (Courtesy of Drs. A. C. Francesconi do Valle and R. R. Guimaras, Rio de Janeiro)

 

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Imaging Diagnosis

When the lungs are involved, there can be two patterns: a benign self limiting form and another in which there is slow progression (Fig. 6.55).

"Benign" Pulmonary Form. In many patients the chest radiograph is normal. In others there may be bilateral air space consolidation, often more than is expected clinically, but with no specific distribution. Thin-walled cavities may develop. There is often quite marked hilar adenopathy. As healing takes place there is local fibrosis and an increased interstitial pattern. Calcification either in the lungs or lymph nodes is unusual.

High-resolution CT is the most accurate way to image early paracoccidioidomycosis: scans show peribronchial and septal thickening and later will confirm the cavitation, alveolar consolidation, scarring, and associated emphysema (Fig. 6.56). Micronodules may be seen and hilar adenopathy is clearly demonstrated.

Progressive Pulmonary Form. Chest imaging shows slowly progressive, bilateral patchy alveolar consolidation, with nodulation in some patients. Solitary pulmonary nodules are uncommon. The lower lobes may be slightly more affected than other parts of the lungs, but there is no characteristic distribution. In some patients the lung lesions are the result of aspiration pneumonia from the buccal ulceration. It has been suggested, but not proven, that this is one of the reasons for the slightly predominant basal location. There is lymphadenopathy, but it is not so marked as in the benign form. Pulmonary fibrosis may progress significantly to cause cor pulmonale. Pleural effusions are uncommon.

In general, the radiographic appearance of the chest resembles tuberculosis or other fungal infections (Fig. 6.55).

Gastrointestinal Form. In some patients there is a palpable abdominal mass, but plain radiographs of the abdomen are normal: ultrasonography shows lymphadenopathy. In other patients, abdominal radiographs show distended loops of bowel with fluid levels, suggesting partial obstruction. In disseminated infections, ultrasonography shows ascites and marked mesenteric lymphadenopathy. Lymph node calcification has been noted, but the pattern is nonspecific.

Contrast studies of the small intestine in the early stages of infection show mucosal nodulation, sometimes with central ulceration. There may be segmental small bowel spasm and there is often hypersecretion. As the infection progresses, lengths of bowel become thickened and rigid, with irregular spiky and edematous mucosa. Several centimeters of bowel may show distorted mucosa, eventually becoming narrow and rigid, with decreased peristalsis, but with almost normal intervening segments of bowel (Fig. 6.57 A-D). Later in the infection, strictures develop and are usually localized, the result of scarring. Ileocolic and ileocecocolic intussusceptions may occur. An inflammatory mass may develop in the ileocecal region, causing the cecum to contract or, in some cases, distend. The cecal outline may become conical. In the colon there is a similar pattern, with localized or diffuse narrowing, particularly in the ascending colon (Fig. 6.57E). Any part of the colon may be involved; in some patients almost the whole large bowel is affected, but in others there are intervening normal segments. Stenosed areas can be single or multiple, and may be found at any level, including the rectum (Fig. 6.57 F). There may be pseudodiverticuli and fistulae.

Regardless of the extent of the abdominal infection, standard chest radiographs may initially be normal, but high-resolution CT may show changes previously unsuspected on routine chest radiographs.

Loops of jejunum and upper ileum in which the normal pattern has disappeared: some segments are dilated and others narrowed. The lower ileum is still normal. E Diffuse narrowing of the entire cecum and the ascending colon, as far as the hepatic flexure. The mucosal pattern has been replaced with nodulation. The terminal ileum and transverse colon appear normal. F Severe localized stenosis of the upper rectum, with nodular mucosa above and below it. All these patients are adult males.

Involvement of Other Sites. Paracoccidioidomycosis does not usually infect the urinary tract primarily, but distortion or displacement of the ureters and occasionally the kidneys can be caused by retroperitoneal infection. Ultrasonography is the most useful survey examination, but excretory urography will show the ureteric status more accurately and is another way to exclude hydronephrosis. Bladder infection is only likely to occur after contamination, e. g., following catheterization.

Hepatic, splenic, and adrenal granulomas may be recognized by MRI, CT, or ultrasonography. Similarly, cerebral granulomas or meningeal infection are well shown on MRI or CT scanning (Fig. 6.58).

Skeletal involvement by paracoccidioidomycosis is rare, even in the widely disseminated systemic infections. Lytic lesions may develop in the most vascular part of any bone (Fig. 6.59).

In the mandible and maxilla there may be rarefaction and loss of clarity of the alveolar margin: if the infection is extensive, teeth may be lost. There are no characteristic imaging findings, and it is very unlikely that bone infection will occur in the absence of systemic disease.

Differential Diagnosis

In an endemic area it is not difficult to establish the diagnosis; however, elsewhere it is not easy to distinguish paracoccidioidomycosis from other mycotic infections or from amebiasis, tuberculosis and, in the abdominal form, Crohn's disease (regional ileitis). The finding of disseminated skin lesions, including perianal or penile nodules, or involvement of bones or joints makes the diagnosis more likely.

Nevertheless, microscopy and identification of the fungus is essential.
The most important factors in making the diagnosis of paracoccidioidomycosis are epidemiology and a high index of suspicion.

 

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