Fig. 6.43. Coccidioidomycosis mimics tuberculosis in the variety and multiplicity of images which may be seen, a few of which are illustrated in this and the next four figures. A The pulmonary lesions in 54 patients. B Miliary spread throughout both lungs with marked hilar and mediastinal lymphadenopathy. C Lymphadenopathy without obvious pulmonary foci. D The ring, "grape skin" cavity which is so typical of this infection. E A large fluid-containing cavity in an upper lobe, seen in a lateral projection (arrows show fluid-level). F A peripheral coccidiodaoma with a small pleural effusion. (A courtesy of Dr. J. P. McGahan; Sacramento; D courtesy of Dr. J. P McGahan et al and A]R, 1981)

Imaging Diagnosis

The small calcified granulomas or scars seen in the lung in asymptomatic coccidioidomycosis have already been noted: another finding on a plain chest radiographs is localized pleural thickening.

When the patients has symptoms, the chest radiograph often shows consolidation, commonly in the upper lobes, or fleeting nodular or bronchopneumonic densities in the middle and lower lobes: these may coalesce to lobar consolidation or break down into small but multiple cavities (Fig. 6.43). Pneumonia may persist, or become fibrotic and, with healing, can develop calcification. If the disease is progressive, the small cavities are joined by tissue breakdown into one large cavity: this may persist or heal with fibrosis. However, some of the linear densities, particularly in basal regions, may be peribronchial or lymphatic thickening and not fibrosis.
At all stages, hilar lymphadenopathy is common (Fig. 6.43 A); the mediastinal nodes are enlarged less frequently. There can be lymphadenopathy even when there is no visible parenchymal lesion (Fig. 6.43 C) and this may persist for months: the etiology of such lymphadenopathy cannot be recognized by imaging alone.

Pleural involvement, with pleural effusion and thickening, is quite common and a pneumothorax and empyema can also occur.

A solitary nodule, a coccidioidoma (Fig. 6.43 F), is often clear in outline and very similar to a tuberculoma. Such nodules can be 0.5-2 inches (1-5 cm) in diameter, and are usually single but occasionally multiple. CT or standard tomography sometimes shows central calcification. Aspiration biopsy is necessary to establish the diagnosis. It has been suggested that the location of these nodules in different parts of the lung is a way to distinguish them from tuberculomas. Unfortunately, both coccidioidomas and tuberculomas may occur in any part of the lung, and both may remain unchanged for months and may either grow slowly or cavitate. Calcification can occur in both infections. In tuberculosis, changes in the patient's immunity can result in breakdown of the nodules with local or distant spread: this is rare in coccidioidomycosis. A coccidioidoma does not represent the threat of bronchogenic spread which occurs with a tuberculoma.

All patterns of the disease can be unilateral or bilateral. As already noted, there may be linear densities, particularly in basal regions, which may be peribronchial or lymphatic thickening. Miliary lesions in the
lung (Fig. 6.43 B) usually denote hematogenous spread and are usually accompanied by extrapulmonary dissemination. A reticulonodular pattern, resembling but larger than that in miliary tuberculosis, can be seen in AIDS patients with coccidioidomycosis: if there is cavitation, the prognosis is poor.

In the chronic, benign pattern of pulmonary infection, the most characteristic finding is a thin-walled cyst, with or without bronchial communication. These "grape skin" cavities (Fig. 6.43 D) have no apparent surrounding parenchymal reaction, but the wall of the cavity is often several millimeters thick. Serial films may show progression, from thick-walled to thin-walled cysts, and rapid inflation and deflation. These cysts may be secondarily infected, contain a fungus ball, heal with fibrosis, be filled with blood by internal hemorrhage, or rupture and produce a pneumothorax. Although strongly suggestive of coccidioidomycosis, similar thin-walled cavities occur in tuberculosis, melioidosis, and dirofilariasis. In some patients, the cavities are thick walled and even less specific, but a very thick-walled cavity F with a central lucency (a "doughnut cavity") may favor the diagnosis of coccidioidomycosis.