Chronic fungal osteomyelitis of the tibia due to Acremonium curvulum: a rare case

Fungal osteomyelitis is a rare disease which usually presents in an indolent manner. Opportunistic infections due to other non-aspergillus moulds are an emerging entity. We report a case of fungal osteomyelitis due to Acremonium spp in an immunocompetent adult which showed a chronic, indolent course but responded well to treatment with voriconazole. This case highlights the importance of diagnosing the causative agent in fungal osteomyelitis as species specific susceptibility can aid in the treatment of fungal osteomyelitis.


Introduction
Fungal osteomyelitis is a rare disease which usually presents in an indolent manner. It affects both immunocompetent and immunocompromised individuals. The possible ways to acquire fungal osteomyelitis include direct inoculation post traumatic injuries contaminated with soil, open wounds or surgery, hematogenous spread or extension from a contiguous site of infection [1]. A majority of these infections are caused by Candida spp and Aspergillus.
Dimorphic fungi and Cryptococcus spp are also implicated as etiological agents of fungal osteomyelitis. Opportunistic infections due to other non-aspergillus moulds are an emerging entity [2,3]. As they are reported infrequently, their mechanism of infections and clinical outcomes remain poorly described. We report a case of fungal osteomyelitis due to Acremonium spp in an immunocompetent adult which showed a chronic, indolent course but responded well to treatment. Fungal osteomyelitis due to Acremonium spp are rarely reported with three cases previously reported in transplant recipients [4][5][6].

Patient and observation
A 59 year old male was admitted to the orthopaedic ward with complaints of multiple draining sinuses in the right calf since 3 weeks.
He gave history of 2 episodes of similar draining sinuses at a site above the current sinus which occurred 15 years back. At that time he had not sought any treatment and the sinus had healed by itself.
Currently, the patient complained of severe pain and bloody discharge from the sinuses. He gave history of taking antibiotics prescribed by local physicians. There was no history of trauma, fever, chronic cough or loss of weight and appetite. The patient was a diabetic since the past ten years and was on oral hypoglycaemic agents. On examination of the right leg, two sinuses were present on the anterior aspect of the tibia in the proximal 1/3 rd portion. Blood stained purulent discharge was observed in both these sinuses. Another sinus was observed in the posterior calf region, without any discharge.
Tenderness was elicited around the sinuses. No neurovascular deficits were observed and distal pulse and movements were preserved. Xray of the right lower limb showed cortical thickening of the right tibia

Discussion
Fungal osteomyelitis was considered a rare entity till recently [7]. The knee [11]. Secondly the organism is morphologically and clinically indistinguishable from Fusarium spp during its early phase of growth [12]. Invasive Acremonium infections are secondary to immunosuppression due to malignancy, medication and transplantation [13]. Since Acremonium spp are common environmental saprophytes, it is essential to confirm the infection by histopathology. As seen in our case, the histopathological picture was suggestive of chronic fungal osteomyelitis. Treatment of nonaspergillus osteoarticular infections usually involves combined surgical and medical approach [14] .Optimal antifungal therapy for Acremonium infections is still debatable due to the paucity of reported cases. Amphotericin B, ketoconazole, itraconazole, fluconazole, 5-fluorocytosine, voriconazole and combinations of these antifungal drugs have been tried with variable success [6].
Amphotericin B has been used to treat serious infections in most cases; patients with poor response to amphotericin B have shown resolution with voriconazole [15,16]. In the described case, voriconazole showed good response initially and was continued for 6 months. The patient remained asymptomatic during his last visit to the hospital, which was 24 months after his therapy was completed.

Conclusion
This case highlights the importance of diagnosing the causative agent in fungal osteomyelitis. Species specific susceptibility can further aid treatment in fungal osteomyelitis. Voriconazole treatment as seen in this case shows good response and is easier to administer during the prolonged course of treatment required for fungal osteomyelitis.