Primary infection, although poorly understood due to lack of data, is thought to occur through inhalation of the conidia through the respiratory tract, after inhaling fungal conidia produced by the mycelial form of P. brasiliensis. This occurs predominantly in childhood and young adulthood, after exposure to agricultural activity. Infection may occur through direct skin inoculation, although this is rare. After inhalation into the alveoli, there is rapid multiplication of the organism in the lung tissue, sometimes spreading via the venous and lymphatic systems. Approximately 2% of people develop clinical features after the initial asymptomatic infection. The type of immune response determines the clinical manifestation of the infection, with children and HIV co-infected individuals most commonly developing the acute/subacute disseminated disease. Most of those infected develop a Type 1 T-cell (Th1) mediated immune response, resulting in alveolitis and compact granuloma formation that control fungal replication, and latent or asymptomatic infection. It then is thought to remain dormant in residual lung lesions and mediastinal lymph nodes. A deficient Th1 cell response results in the severe forms of the disease. In these individuals, granulomas do not form, and the affected person develops Th2 and Th9 responses, resulting in activation of B lymphocytes, high levels of circulating antibodies, eosinophilia, and hypergammaglobulinemia. Lung involvement subsequently occurs after a dormant phase, manifesting in upper respiratory tract symptoms, and lung infiltrates on imaging. The commonest, chronic form, is almost certainly a reactivation of the disease, and may develop into progressive scarring of the lungs (pulmonary fibrosis). It can cause disease in those with normal immune function, although immunosuppression increases the aggressiveness of the fungus. It rarely causes disease in fertile-age women, probably due to a protective effect of estradiol.
Paracoccidioidomycosis
Leukemia
Chromoblastomycosis
Lymphoma
Coccidioidomycosis
Tuberculosis
Conidiobolomycosis
Phaeohyphomycosis