Fungal and Mycobacterial Septic Arthritis and Osteomyelitis of the Extremities

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Authors: Zalavras CG, Papasoulis E, Hindoyan K, Holtom PD, Patzakis MJ
University of Southern California, Los Angeles, CA

Title: Fungal and Mycobacterial Septic Arthritis and Osteomyelitis of the Extremities

Background: Fungal and mycobacterial bone and joint infections are rare and their diagnosis is often missed or delayed. The literature is inconclusive on parameters that could assist in diagnosis of these infections

Hypothesis/Purpose: The aim of our study is to identify the clinical, laboratory, and microbiological features of fungal and mycobacterial infections of the extremities

Methods: This is a retrospective study of adult patients diagnosed in our institution with osteomyelitis and/or septic arthritis of the extremities due to atypical organisms from 1993 to 2012. We identified 48 patients (mean age 46 years). Thirty-five infections (73%) were fungal, 12 (25%) were mycobacterial, while one (2%) was due to both types of organisms. Nineteen patients (40%) had osteomyelitis, 7 (15%) had septic arthritis, and 22 (46%) had septic arthritis with adjacent osteomyelitis

Results: Associated comorbidities were present in 65% of patients. Infection was hematogenous in 42% of cases, whereas it developed by local spread or direct inoculation in 58%. The clinical picture included pain in 68% and discharge in 50% of patients. Median delay from reported onset of symptoms to suspicion of an atypical microorganism and procurement of appropriate specimens/cultures was 41 days (7 days to 9 years).

White blood cell count was elevated in 36% of patients, erythrocyte sedimentation rate (ESR) in 94%, and C-reactive protein (CRP) in 90% of patients. Elevated ESR or CRP was present in all patients.

Candida albicans was the most common fungus isolated (36%, 13/35). Mycobacterium tuberculosis was the most common mycobacterium (77%, 10/13). A co-existing bacterial pathogen was isolated in 77% (37/48) of cases. Mycobacterial infections had a significantly higher rate of hematogenous spread (92% vs. 23%, p<0.001), involvement of joints (100% vs. 44%, p<0.001), and delayed diagnosis (214 vs. 35 days, p<0.001)

Discussion: Fungal and mycobacterial infections of the extremities occur in the absence of comorbidities in one third of cases and are diagnosed with a considerable delay. Elevated ESR and CRP have high sensitivity for these infections. Co-existing pathogens are isolated in the majority of cases and may be more common than previously reported

Conclusion: Fungal and mycobacterial osteoarticular extremity infections have similar clinical and laboratory characteristics. Diagnosis of these infections is delayed; therefore a high index of suspicion is needed