Fungal arthritis is an infection of a joint by a fungus.
A normal person is quite resistant to fungal infection.
Fungal infection is known to be an opportunistic infection.
Alteration of human flora, disruption of mucocutaneous membranes and impairment of the immune system may predispose to the fungal infection.
Fungi may enter the joint by hematogenous spread or direct inoculation by means of trauma, injection in the joint or joint aspiration.
Hematogenous spread is the most common method of infecting a joint.
The infection of the joint may occur in the isolation or as a part of the multisystem infection.
Fungal arthritis is also called mycotic arthritis. It is quite rare.
Organisms and Risk of Infection
Conditions that may cause fungal arthritis include
- Blastomycosis
- Candidiasis
- Coccidioidomycosis
- Cryptococcosis
- Histoplasmosis
- Sporotrichosis
- Exserohilum rostratum
- Aspergillus
Fungal arthritis in people with normal immunity is rare.
The condition is known to occur with use of contaminated injections but otherwise, fungal infection is quite rare in healthy people.
However, people with abnormally suppressed immune systems are at risk for fungal infections, including fungal arthritis. This includes people with severely low white blood counts (neutropenia), HIV infection, injection drug abusers, and those taking chronic cortisone medication.
Candida infection involving a single joint, usually the knee, hip, or shoulder, results from surgical procedures, intraarticular injections, or among critically ill patients with debilitating illnesses such as diabetes mellitus or hepatic or renal insufficiency and patients receiving immunosuppressive therapy.
Candida infections in intravenous drug users typically involve the spine, sacroiliac joints, or other fibrocartilaginous joints. Unusual cases of arthritis due to Aspergillus species, Cryptococcus neoformans, Pseudallescheria boydii, and the dematiaceous fungi have also resulted from direct inoculation or disseminated hematogenous infection in immunocompromised persons.
Presentation
Fungal arthritis is considered when a patient whose immune system is compromised develops inflammation of a joint. Symptoms of fungal arthritis include pain, heat, swelling, warmth, redness, and loss of range of motion of the affected joint. The most common joint to develop fungal arthritis is the knee joint. Fever may or may not be present.
Symptoms of fungal arthritis typically become manifest weeks to months after the initial infection of the joint.
Lab Studies
Blood tests can include testing the blood for the white blood count, inflammation markers like ESR, and CRP, and cultures of the blood. Joint fluid is aspirated from the joint with a needle and syringe and this fluid is analyzed in the laboratory to culture the precise fungal organism and establish the diagnosis.
The synovial fluid in fungal arthritis usually contains 10,000 to 40,000 cells/µL, with about 70 percent neutrophils. [compare with bacterial arthritis where the count is >50000 and about 90% of the cells are neutrophils]
Stained specimens and cultures of synovial tissue often confirm the diagnosis of fungal arthritis when studies of synovial fluid give negative results.
Imaging
Routine xrays, CT scanning, and MRI can tell about character and extent of joint damage.
Plain radiography may reveal only a joint effusion in the early stages of infection.
Joint space narrowing is late finding and is often difficult to interpret because of preexisting joint disease.
CT is helpful in joints with small spaces like the sternoclavicular joint.
MRI is most useful in assessment and can delineate periarticular osteomyelitis as a causative mechanism as well.
Radionuclide studies have poor specificity.
Treatment of Fungal Arthritis
Treatment consists of drainage and lavage of the joint and systemic administrations of amphotericin B, fluconazole, or itraconazole (the exact drug depending on the species involved). The doses and duration of therapy are the same as for disseminated disease. Intraarticular instillation of amphotericin B has been used in addition to intravenous therapy.
The outlook for fungal arthritis is directly related to how much damage occurs to the cartilage and bone of the joint. Earlier treatment leads to optimal outcomes.
