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 immunocompromised males. In patients with brain involvement, mortality exceeds 80%; in other forms, mortality is about 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.

Pulmonary infection

Neurological infection

Cardiac conditions

Lymphocutaneous disease

Ocular disease