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Fig. 6.27 A-D. The histopathology of zygomycosis. A The granuloma around a hyphae. There are many epithelioid and giant cells and there are usually plasma cells, macrophages, lymphocytes, and neutrophils. H & E, x400. B Three transverse sections of hyphae and heavy infiltration of eosinophils surrounded by the Splendore-Hoeppli phenomenon. PAS, x200. C Entomophthoromycosis caused by Basidiobolus haptosporus. There are many hyphae, and a few show septations. Gomori methenamine-silver, x450. D A myocardial vessel occluded by a septic thrombosis which contained "twisted ribbon" hyphae characteristic of a zygomycete. Septic thrombosis and septic infarction are common complications of disseminated zygomycosis, and are often fatal, as in the case. Gomori methenamine-silver, x400. (A-C courtesy of Bittencourt and Londero 1995; D courtesy of Dr. D. H. Connor)

 

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Clinical Characteristics

Both types of zygomycetes have similar clinical patterns. Both have a subcutaneous, a mucocutaneous, and a visceral form. Although it is important to differentiate the organisms to provide the correct treatment, it is not possible to do this clinically or by imaging.

The mucocutaneous or subcutaneous forms (Fig. 6.28) present as nodules, or an area of induration involving the limbs or buttocks, increasing steadily and spreading to cause gross disfiguration. The infection begins as a single area of erythematous, thickened and slightly painful cellulitis which quite rapidly develops a central area of black necrosis with a well-defined edge. The appearance may differ if the infection has arisen where there has been previous trauma. The nodules become confluent and in some patients there may be multiple lesions. As the disease advances, it may be mistaken clinically for a malignant tumor. It is usually the disfiguration (Fig. 6.29 A, B) which brings the patient to the clinic or hospital.

Both subcutaneous and mucocutaneous infections can spread to muscle and underlying bones (Fig. 6.28 D) or to lymph nodes and may even involve adjacent organs. The facial form is good example of this. It has been called rhinocerebral or craniofacial mucormycosis and may originate in the paranasal sinuses. From there it may spread to the orbit, palate, or brain. The initial clinical presentation is acute sinusitis, with fever and sinus headache. There is a purulent nasal discharge in most patients. Progress is rapid over a few days, with increasing edema and areas of black necrosis. The palate may be perforated. The patient may complain of double vision or there may be cranial nerve palsy. Blindness hs been one result: thrombosis of the cavernous sinus or carotid cavernous fistula may occur and the thrombosis may extend to the bifurcation of the carotid artery or cause cerebral embolization or infarction. This is a severe destructive and painful disease, progressing rapidly to death.

Pulmonary infection is usually associated with widespread disseminated disease; however, in some immunosuppressed patients there is direct lung, infection following the inhalation of spores (Fig. 6.29 C). The onset is acute and nonspecific, with cough, fever, shortness of breath, pleural pain, and sputum. The immediate clinical diagnosis will be pneumonia. The infection progresses rapidly, but sputum cultures reveal no bacteria. Fine-needle aspiration biopsy or open lung biopsy may be required to establish the diagnosis. Bronchoscopy may fail to find the organism, particularly when there has been lung infarction.

The visceral form of mucormycosis (Fig. 6.30) starts clinically with loss of weight, abdominal pain, enteritis, and, in some patients, dysuria. In children in particular, there may be an abdominal mass and the clinical diagnosis may be lymphoma, schistosomiasis, or tuberculosis. The fungal mass can cause intestinal obstruction or, when the kidneys are involved, hydronephrosis; there may be bladder infection.

In about half the patients with gastrointestinal mucormycosis, the stomach is involved; in about a third, the colon; and less frequently, the esophagus and small intestine. In the stomach there is usually a necrotic ulcer, which may be deeply penetrating. This is the form often seen in malnourished children or in diabetics. The gastric ulcers may perforate, causing pain, which may be the presenting symptom. Localized mucormycotic granulomas can occur anywhere within the bowel and be mistaken for tumors.

 

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