- A rare infectious disease caused by Nocardia spp. which are primarily located in ground and water sources
- No pathognomonic presentation
- Nocardiosis can be acute, subacute, or chronic, and involves multiple systems:
- Pulmonary (>70% overall, 39% only lung)
- Disseminated: ≥2 sites (32% overall)
- Cutaneous (~8%)
- CNS (20% overall, 44% of disseminated, 9% brain only)
- Patients are typically immunocompromised or have chronic pulmonary or systemic disease.
- Less commonly, Nocardia can infect the eye, heart, bone, soft tissues, and any other organ system.
- Overall: 0.4/100,000 cases per person-years
- >60% are immunocompromised.
- All ages are susceptible; mean age at diagnosis is in 4th decade of life.
- Male > female (3:1)
- ~500 to 1,000 cases per year in United States; not reportable
- HIV/AIDS: 53/100,000 cases per person-years
- Bone marrow transplant recipients: 128/100,000 cases per person-years
- Solid-organ transplant recipients: 1,122/100,000 cases per person-years
Etiology and Pathophysiology
- Nocardia spp. are aerobic gram-positive branching rods found worldwide in soil, decaying plants, fresh and salt water.
- >80 species, >30 of which cause human disease.
- Nocardia asteroides complex causes the majority of symptomatic infections and includes Nocardia abscessus, Nocardia cyriacigeorgica, Nocardia farcinica, and Nocardia nova.
- Nocardia enters through inhalation (e.g., contaminated dust), traumatic skin inoculation, or ingestion.
- Nocardiosis of the skin has four patterns: primary cutaneous, lymphocutaneous, cutaneous secondary to disseminated spread, and mycetoma.
- Pulmonary, CNS, and other organ system infection with Nocardia is typically suppurative, often leading to abscess formation.
- Incubation period: days to weeks
- Pathologic Nocardia spp. have several intrinsic means of overcoming host immune responses.
- Most cases occur in immunocompromised hosts, particularly those with impaired cell-mediated immunity. Other chronic diseases (e.g., diabetes mellitus [DM], COPD) may predispose individuals to nocardiosis.
- Farm workers and other immunocompetent individuals may develop pulmonary, cutaneous, and disseminated disease if sufficiently exposed.
- Nocardiosis can be severe and fatal in immunocompromised patients; immunocompetent individuals rarely develop severe disease.
- Immunocompromised children are also at risk.
Commonly Associated Conditions
- Chronic pulmonary disease
- Hematologic and other malignancies
- Bone marrow and solid-organ transplantation
- Chronic corticosteroid therapy
- Autoimmune diseases
- Tumor necrosis factor therapy
- Kidney failure
- Cirrhosis and alcoholism
- TB and other granulomatous disease
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