Treatment of Fusarium Osteomyelitis in a Diabetic Foot Ulcer Complicated by Antineoplastic Chemotherapy

Tyson O. Strom, DPM; Rebecca A. Burmeister, DPM, MPH; Gary M. Rothenberg, DPM, CWS; Sari J. Priesand, DPM

Disclosures

Wounds. 2022;34(4):e37-e41. 

In This Article

Discussion

Treating DFO can be especially difficult when patients are severely immunocompromised. Patients with AML may present with leukocytosis, anemia, and thrombocytopenia.[8] Patients undergoing chemotherapy for AML will have further barriers in the diagnosis and treatment of DFO. On presentation, the current patient had a clinically suspected bone infection. The physical examination showed erythema, edema, drainage, and a positive probe-to-bone test. The ability to probe to bone is associated with high specificity for osteomyelitis, exceeding 90%.[3] The inflammatory biomarkers, ESR, and CRP, are routinely ordered for evaluating DFIs. An ESR of 60 mm per hour and a CRP level of 7.9 mg/dL are the evidence-based cutoff points for predicting osteomyelitis.[9] Although the patient had an elevated ESR, it was subthreshold for DFO. The CRP level was elevated above the cutoff point, and a diagnosis of osteomyelitis with an elevated CRP level has a sensitivity of 49% and specificity of 80%.[9]

Regarding imaging workup of suspected osteomyelitis, it is recommended to begin with plain film radiographs (anteroposterior, oblique, and lateral). The patient's radiograph displayed cortical irregularity and lucency of the distal phalanx. It typically takes 3 weeks for a cortical erosion to develop and it may not be evident until the late stages of the disease.[4] Due to the time it may take to see cortical erosions on radiographs, and for surgical planning, the decision was made to obtain an MRI to evaluate the extent of the infection. Magnetic resonance imaging is the most accurate imaging test for the assessment of suspected osteomyelitis, with a sensitivity of 90% and specificity of 79%.[4] Short T1 inversion recovery (STIR) images are the most sensitive sequence type to evaluate for osteomyelitis.[4] In the current case, MRI revealed positive changes consistent with osteomyelitis to the distal phalanx without signs of abscess.

The histopathology of the current case showed a bone culture growth of coagulase-negative staphylococci and Fusarium species. Coagulase-negative staphylococci are ubiquitous microbes that recently have become more commonly associated with nosocomial infections. The human integument is the natural reservoir for Staphylococcus epidermidis, the most common coagulase-negative staphylococci. It has the greatest pathogenic potential of all species of coagulase-negative staphylococci and can be challenging to manage.[10]Fusarium species are filamentous fungi present as saprophytes in soil and animals.[11] The widespread distribution of Fusarium species is attributed to their ability to grow on a wide range of substrates and their efficient mechanisms for dispersal.[12]Fusarium was first reported as a systemic pathogen in 1973 and subsequently has been noted to cause an increasing number of infections, particularly in patients who are severely immunocompromised.[13]Fusarium species have been reported to cause cutaneous infections in patients with diabetes. They can develop after skin breakdown at the infection site.[11] Invasive fusariosis has been shown to occur in patients receiving high doses of corticosteroids and those with prolonged and profound neutropenia.[12] It has been shown to respond poorly to medical management by antifungal medication, with only 43% of patients with fusariosis having a complete or partial response.[11] Therefore, the treatment of Fusarium osteomyelitis usually requires the use of both antifungal therapy and surgical debridement, which occurred in the current case.[13]

Case reports of Fusarium osteomyelitis in patients who are immunocompromised are extremely rare.[13] One case report noted that there were 10 cases of Fusarium osteomyelitis reported in the literature from 1972 to 2012.[14] Of the 10 case reports, 7 of these infections occurred in individuals who were immunosuppressed. Of the immunocompromised group, in each of the 4 treated with wide surgical debridement or amputation and antifungal therapy, the infection was successfully eradicated. Conversely, none of the 3 patients treated with simple debridement and antifungal therapy had eradication of infection. No case reports of Fusarium osteomyelitis in an immunocompromised individual have demonstrated definitive long-term treatment with simple debridement and antifungal therapy alone.[14]

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