Coccidioidomycosis

A 58-year-old female with no past medical history presented with a 1-month history of a productive cough, breathlessness, lethargy, arthralgia and a rash on both of her legs. On examination, there were right basal crackles and erythema nodosum on both legs. Routine blood tests were normal. Blood and Tuberculosis cultures were negative.

A chest radiograph was performed which showed a small cavitating lesion in the left upper lobe (Fig.1). Consequently, a CT thorax was performed with contrast which showed a 1.3 cm cavitating nodule in the left upper lobe suspicious for malignancy although, infective/inflammatory aetiology remained a possibility at this stage (Fig.2). As a result, a fluorodeoxyglucose PET CT scan was executed which depicted the cavitating lesion with low-grade up-take and no further pathological uptake throughout the body (Fig.3). It was therefore concluded that the lesion was more likely to be infective rather than a malignancy.  The patient was a frequent traveller and often visited Arizona for camping trips. A sample was sent for culture and serology for a possible fungal infection however these came back negative. It was decided that we would watch, wait and treat with antibiotics. Two months later, another CT thorax was performed which showed no improvement of the lesion (Fig.4).

Coccidioides is a dimorphic fungus which denotes that it can exist in two morphologies depending on its environment. In the external environment, it exists as mycelia and in vivo, it converts to spherules. There are two species C.immitis and C.posadasii. The former is found predominantly within California and Arizona. The latter is more widespread around the world. [1,7,8] 

Once inhaled in sufficient amounts, it can lead to an infection known as Coccidioidomycosis. Anthroconidia are the infectious spores that congregate in the alveoli before they metamorphose into spherules. Spherules subsequently rupture to enhance the infection. Pulmonary Coccidioidomycosis constitutes 95% of cases. It is mostly self-limiting and resolves in 6 weeks. A minority suffer with a disseminated or chronic form of the disease.  [2,3,7,8]

Incubation period is 7-21 days and can clinically present with a cough (possible haemoptysis), fever, malaise, chest pain, night sweats and fatigue. A disseminated infection may present with cutaneous lesions such as erythema nodosum, miliary pulmonary nodules, extra-thoracic lymphadenopathy and involve the bones, joints and central nervous system.  This is as a result of haematogenous spread. [3,7] 

High-risk individuals are those who are immunocompromised or exposed to aerosolization of soil. These include military personnel, archaeologists, solar-farm workers, construction workers and populations who inhabit areas susceptible to natural disasters such as earthquakes. [3] Most commonly encountered by adults over 40 years. [4]

The most frequent radiological finding is consolidation which can be solitary, multifocal, lobar or segmental. Coccidioides distribution is commonly unilateral with perihilar dominance. Parenchymal changes can range from a ground glass opacification to a dense homogenous consolidation which can mimic a bacterial pneumonia. Other findings include nodules, interlobular-septal thickening, granulomatous lesions, lymphadenopathy and pleural effusions. CT imaging is preferable due to its higher sensitivity and specificity [3,7] 

Coccidioidomycosis can be diagnosed in a multitude of techniques:

• Special stains - methenamine silver
• Serology - Enzyme immunoassay and complement fixation to detect IgM and IgG. The former being highly sensitive and the latter highly specific.
• Bronchoscopy
• CT-guided biopsy
• Surgical biopsy [3,7]

As malignancy remained a possibility, the patient opted to have surgery. She underwent a video-assisted thoracoscopic surgery (VATS). Biopsies retrieved confirmed lung tissue with florid necrotising inflammation, peripheral palisading of histiocytes and well-formed granulomas. No evidence of malignancy. Samples sent for staining and serology were positive for C.immitis. 

Treatment:                                                                                              

• Asymptomatic/mild – no medication, close monitoring.
• Moderate to severe symptoms – Fluconazole or Itraconazole

If symptoms and lesions are persistent despite medication, surgical intervention is advised. [8]