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Fig. 6.49 A-D. Sporotrichosis can be localized or show lynphocutaneous spread. A A verrucous infection on the thumb, resembling chromoblastomycosis. B A more characteristic pattern of lymphocutaneous spread in the skin and subcutaneous tissues of the leg. C A verrucos lesion on the face, with small satellite nodules. D A large ulcerative mucocutaneous lesion in a 6-month-old child: this was misdiagnosed as leishmaniasis. (A, C, D from Bittencourt and Londero 1995; B courtesy of Dr. D. H. Connor)

Fig. 6.50 A, B. Disseminated sporotrichosis. A A destructive lesion starting in the ulna and spreading to affect the upper end of the radius and the elbow joint. There is marked tissue swelling. B A more localized, spiculated lesion at the proximal end of the fifth metatarsal. A and B courtesy of Professor Harold Jacobson)

Fig. 6.51. Cutaneous blastomycosis with a spreading verrucous, ulcerative lesion which had progressed slowly over a number of years. An African man from Zimbabwe

 

 

 

 

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Clinical Characteristics

The patient usually presents with cough, fever, night sweats, and general weakness and may be thought to have tuberculosis. The sputum may be blood stained and purulent, again suggesting tuberculosis. The cutaneous form of infection presents as papules which progress to crusty ulceration, with raised edges: they may assume a warty verrucous appearance and steadily enlarge (Fig. 6.51). Skin lesions are often multiple and most commonly appear on the face and limbs. They are usually painless and may be mistaken for squamous cell carcinoma. Sometimes they have a serpiginous advancing border which causes a mutilating deformity. Atrophic scars develop where there have been old lesions. The underlying bones are affected and sinuses form: there is regional lymphadenopathy. Other lesions can occur in the mucous membranes of the nose, mouth, larynx, and vagina.

Skeletal lesions can occur in up to 25% of all infected patients. The infection can involve any organ, but usually this happens in patients who already have skin or pulmonary blastomycosis.

Systemic infection begins in the lungs and may remain pulmonary or disseminate to cause meningitis, spinal abscess, epididymo-orchitis, prostatitis, osteomyelitis, or arthritis, or to infect any other organ system. Apart from the prostate, B. dermatitidis does not often affect the urinary tract and, even more rarely, the gastrointestinal tract. Dissemination may not develop for years after the initial inoculation. Because there are no reliable laboratory or skin tests, it is difficult to know how many asymptomatic cases there are, or whether reactivation occurs. Overwhelming primary blastomycosis may occur, even in immunocompetent individuals. Diffuse lung infection can lead to adult respiratory distress syndrome (ARDS). If untreated, over 90% of patients will die of the infection.

Imaging Diagnosis

The changes on imaging are very nonspecific and extremely variable.

In pulmonary blastomycosis, the chest images strongly resemble tuberculosis: there may be a primary complex with a small focus of infection in the lung and hilar lymphadenopathy. This may heal. In some. patients there is nonsegmental pneumonia, most frequently in the upper lobes. The air space disease is patchy and confluent, with indistinct outlines: lobar pneumonia is less common. A distinguishing feature from pyogenic pneumonia is the very slow rate of change.

Solitary focal masses are quite common; such masses are usually well defined and distinct and may be up to 10 cm in diameter (Fig. 6.52 A-C). Unlike in some of the other fungal infections, these large solitary nodules are often found around the hila or close to the mediastinum, and may mimic bronchogenic carcinoma.
In other patients there is bilateral and diffuse interstitial thickening, which usually indicates further progression of the infection. Cavitation is perhaps a little less common than in tuberculosis, but may occur in almost any part of the lung (Fig. 6.52 D): there may be single or multiple cavities with thick or thin walls. In the disseminated pattern of the infection there may be miliary pulmonary nodules.

The pleura can be infected, resulting in either thickening or effusion, or both. All patterns of the infection can result in fibrosis.

Lymphangitis and lymphadenopathy (Fig. 6.52 D) are unusual in blastomycosis, occurring in less than 10% in most series. Even less common is spread of the pleural infection into the chest wall.

Musculoskeletal imaging shows that many patients with cutaneous pseudoepithelioma have underlying skeletal involvement. In disseminated infections, multiple bones and joints are affected and scintigraphy is a useful preliminary imaging procedure. There may be skin sinuses, but these are uncommon. The flat and short bones and the ends of the long bones show irregular bone destruction and some have reactive new bone formation.

Soft tissue abscesses may occur and can be accurately delineated by ultrasonography. They are subcutaneous, and occur anywhere throughout the body, not only in the limbs and trunk but also internally. Abscesses have been recorded in the liver, adrenals, pericardium, and myocardium, and within the orbit.

Joints are usually affected by direct spread from a nearby focus because the foci of osteomyelitis are often juxta-articular (as with other fungus infections): cartilage is destroyed. Joint effusions increase the joint space at the start of the infection, but later there is loss of articular and periarticular tissues and subluxation may result. In the end there may be bony fusion.

Spinal involvement resembles tuberculosis, with infection of the vertebral bodies and quite early of the intervertebral disc space. Paravertebral abscesses can develop.

Computed tomography and MR scanning clearly demonstrate the spectrum of blastomycosis. Ulcerating masses within the larynx have been demonstrated, and simulate malignancy. Miliary pulmonary nodules, small granulomas, and patches of pneumonia may be demonstrated a little more clearly by CT than with routine chest radiography. Previously unsuspected calcification in pulmonary foci or in lymph nodes may be seen by CT scanning. MRI is useful in vertebral infections to show the extent of any abscess and to exclude cord involvement.

Unfortunately, all imaging changes are very nonspecific and seldom strengthen a suspected diagnosis of blastomycosis. A history of visiting or living in the endemic regions is a reason to include blastomycosis in the differential diagnosis.

 

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