H. capsulatum infection causes histoplasmosis, which usually occurs in the lungs. The environmental reservoir of H. capsulatum is soil . People acquire H. capsulatum infection usually through the inhalation of conidial forms of the organism present in the environment, such as in soils exposed to chickens. Our case had no obvious source of the infection. He denied a recent history of travel and was living in the countryside in Zhejiang Province, Southeast China, where there are many breeding chickens and ducks in the farmhouses. His father was a chicken farmer and chickens entered his home. He remembered that he used to clean the chicken coop to help his family’s poultry business before he became ill. It is possible that he acquired the H. capsulatum infection from the poultry. Indeed, the prevalence of potential H. capsulatum infection in Southeast China is higher than that in Northwest China .
Infection of immunocompetent subjects with H. capsulatum usually causes either asymptomatic or mild influenza-like illnesses with fever, headache, malaise, cough, and chest pain, which spontaneously disappear within a few days. Infected individuals can carry H. capsulatum for many years. When the patient becomes immunosuppressed he can develop disseminated histoplasmosis that can affect the lungs, central nervous system, liver, spleen, and rheumatologic, ocular, and hematologic systems . However, patients with histoplasmosis in the bone and muscle tissues are extremely rare . There are 25 reported cases of confirmed muscle-bone histoplasmosis. Among them, most patients had disseminated histoplasmosis and there were only six patients who suffered from simple bone histoplasmosis, with a lesion in the distal radius or carpal bones [13–17]. There was only one reported case with lower limb histoplasmosis. A patient with non-Hodgkin's lymphoma also had H. capsulatum infection in the tibia . Therefore, to the best of our knowledge, this is the first report of a localized histoplasmosis osteomyelitis in the fibula in an immunocompetent young boy.
Rather than filling the surgical lesion with bone cement or antibiotic beads as in adult patients, the surgical cavity of the patient was filled with homologous cancellous bone to reconstruct a stable distal tibiofibular syndesmosis and ankle joint. Indeed, radiological images and physical examination have demonstrated that the function and structure of the surgical muscles and bone tissues completely recovered. The patient was able to take part in normal and strenuous exercise, and even soccer. Itraconazole and amphotericin B were listed as the drugs for the treatment of histoplasmosis . Amphotericin B has been accepted as a standard drug for the treatment of patients with severe illness, but it occasionally has severe side-effects. Amphotericin B has been recommended for induction therapy for disseminated histoplasmosis in patients with acquired immunodeficiency syndrome, and either amphotericin B or an oral azole antifungal agent (itraconazole) for maintenance. Conazoles can be used as an alternative for the treatment of disseminated histoplasmosis, and itraconazole may be used for both induction and maintenance treatment . However, according to itraconazole labeling, there is not enough evidence for its use in children. Consequently, we treated the 11-year-old boy with voriconazole, a conazole with clear labeling and guidance for its use in teenagers. The prognosis was very satisfactory, as the follow-up results indicated.
In summary, we report a unique case of localized histoplasmosis osteomyelitis without evidence of immunocompromise. This disease was difficult to diagnose using common radiological examinations. We found that surgical removal of the lesion and local treatment with autologous bone transplantation, together with systemic treatment with antibiotics were effective for the control of infection and functional recovery.
Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent (in Chinese) is available for review upon requested.