Autoimmunity Mimics: Infection and Malignancy

Key points

Bacterial infections of the bone, joint, and soft tissue

Bacterial infections of the bone and joint are true emergencies. Permanent disability and death may result if prompt effective treatments are not instituted.¹

Viral arthritis

Viral infections are ubiquitous worldwide, and many have been associated with articular and extraarticular rheumatic manifestations. With globalization, novel virus-associated arthritides are becoming apparent in the United States, including Chikungunya and Zika virus. See Table 3 for rheumatic manifestations of clinically important viral infections.26, 27, 28, 29, 30, 31, 32

Mycobacterial disease

Infection with mycobacterial organisms may result in musculoskeletal disorders. These infections are most commonly seen in immunocompromised patients.

Fungal disease

A number of potentially pathogenic fungi are endemic to the United States, and may have musculoskeletal manifestations. These infections typically occur in immunocompromised persons, and manifestations such as pulmonary or cutaneous involvement are important clues to the diagnosis. Histoplasmosis, coccidioidomycosis, blastomycosis, and cryptococcosis are the most likely to be seen in clinical practice in the United States; however, infections are relatively uncommon.³⁸

Parasitic disease

In certain geographic areas of the world, parasitic infections are an important cause of arthritis, sacroiliitis, myositis, and vasculitis. Parasitic rheumatism should be suspected in patients with rheumatic manifestations with poor response to antirheumatic drugs, prior residence or travel in an area of endemic parasitosis, and peripheral blood eosinophilia. The diagnosis is based on clinical history as well as specialized testing and histopathology in consultation with infectious disease

Malignancy-associated rheumatic disorders

Musculoskeletal manifestations are common in patients with malignancy. The mechanisms underlying these musculoskeletal symptoms include (1) direct tumor invasion of bones and joints, (2) paraneoplastic effects, and (3) chemotherapeutic adverse effects.

Summary

Many factors contribute to the development of musculoskeletal rheumatic syndromes. A plethora of different infectious agents may produce osteoarticular and soft tissue manifestations; likewise, malignancies may manifest rheumatic symptoms via direct invasion or paraneoplastic effects. Awareness of these diseases and their clinical risk factors should result in earlier recognition and intervention, which may improve long-term outcomes and overall patient care.