Nocardiosis is an infectious disease affecting either the lungs (pulmonary nocardiosis) or the whole body (systemic nocardiosis). It is due to infection by a bacterium of the genus Nocardia, most commonly Nocardia asteroides or Nocardia brasiliensis. It is most common in adult males, especially those with a weakened immune system. In patients with brain nocardia infection, mortality exceeds 80%; in other forms, mortality is 50%, even with appropriate therapy. It is one of several conditions that have been called "the great imitator". Cutaneous nocardiosis commonly occurs in immunocompetent hosts and is caused in 80% of cases by Nocardia brasiliensis. Signs and symptoms Pulmonary infection Produces a virulent form of pneumonia (progressive) Night sweats, fever, cough, chest pain Pulmonary nocardiosis is subacute in onset and refractory to treatment with standard antibiotics Symptoms are more severe in immunocompromised individuals Radiologic studies show multiple pulmonary infiltrates, with a tendency to central necrosis Neurological infection Headache, lethargy, confusion, seizures, sudden onset of neurological deficit CT scan shows cerebral abscess Nocardial meningitis is difficult to diagnose Cardiac conditions Nocardia has been highly linked to endocarditis as a main manifestation In recorded cases, it has caused damage to heart valves whether natural or prosthetic Lymphocutaneous disease Nocardial cellulitis is akin to erysipelas but is less acute Nodular lymphangeitis mimics sporotrichosis with multiple nodules alongside a lymphatic pathway Chronic subcutaneous infection is a rare complication and osteitis may ensue May be misidentified and treated as a staph infection, specifically superficial skin infections Cultures must incubate more than 48 hours to guarantee an accurate test Ocular disease Very rarely, nocardiae cause keratitis Generally there is a history of ocular trauma Disseminated nocardiosis Dissemination occurs through the spreading enzymes possessed by the bacteria Disseminated infection can occur in very immunocompromised patients It generally involves both lungs and brain Fever, moderate or very high can be seen Multiple cavitating pulmonary infiltrates develop Cerebral abscesses arise later Cutaneous lesions are very rarely seen If untreated, the prognosis is poor for this form of disease Causes Normally found in soil, these organisms cause occasional sporadic disease in humans and animals throughout the world. Another well publicized find is that of Nocardia as part of the oral microflora. Nocardia spp. have been reported in the normal gingivae and periodontal pockets along with other species such as Actinomyces, Arthromyces and Streptomyces spp. The usual mode of transmission is inhalation of organisms suspended in dust.