Blastomycosis is an uncommon mycotic infection, endemic in North America, but substantially unknown in Europe. This mycotic disease is rare among children and adolescents, representing only 3-10% of the cases
. In children, the lungs are most frequently involved. Extrapulmonary or disseminated blastomycosis occurs in approximately 10% of children and is usually heralded by prior pulmonary symptoms
. A review of known cases diagnosed in Africa between 1951 and 1987 revealed that, among the 81 African patients, bone involvement, with or without extension to the overlying subcutaneous tissues and skin, was the most common presentation of disease
Bone is the third most common site of blastomycotic lesions, after lung and skin. Bones may be involved in 14-60% of cases of blastomycosis, and any bone can be implicated
[5, 6]. Synovial joint involvement has also been reported. Patients with blastomycotic osteomyelitis have pain and swelling at the site, often associated with overlying skin abscess or ulcer. Areas of bone involvement usually appear as lucent (X-ray) or low-attenuation (CT) lesions with indistinct margins but have no radiologic specific features to help distinguish them from other forms of osteomyelitis or neoplasm. Specifically, the lack of periosteal reaction radiographically diverts the differential diagnosis away from osteomyelitis
. Most bone lesions will resolve with antifungal treatment, but in many instances surgical treatment may be necessary, including debridement and curettage
[6, 8, 9]. Children are allegedly unusual host for blastomycosis. As it can mimic other diseases, such as bacterial infection or malignancy, diagnosis can be mistaken or delayed even in endemic Countries. A case occurring in a non-endemic area can represent a Bd transferred from an endemic area, or a reactivation after the patient has moved from an endemic area, as it probably was in our case. Bd grows in a mycelia form at room temperature and it converts to a yeast form within tissues and in culture at 37°C. The rarity of this infection at our latitude justifies the unavailability of specific tests. Culturing the fungus in specific Sabouraud dextrose agar is highly reliable but it requires 2–6 weeks.
Antibodies to Bd detection tests are considered inadequate for diagnosis.
Antigen detection in urine, cerebrospinal fluid (CSF), bronchoalveolar lavage (BAL) fluid, serum and other sterile body fluids has low specificity, being also positive in patients with histoplasmosis and paracoccidoidiomycosis. Methods based on PCR have shown promise but they are not widely available yet
[1, 10]. Direct visualization of single broad-based budding yeast, stained with haematoxylin-eosin, PAS and Gomori methenamine silver (GMS) stain in sputum or tissue samples at microscopy is the primary method with which a diagnosis is made. Bd is not colored by mucicarmine stain, unlike Cryptococcus. As serologic search for antibodies is inadequate for diagnosis and a negative culture does not exclude the possibility of infection, the role of cytology and histopathology was determinant in our case, as already elsewhere described
[9, 10]. Obviously in the absence of PCR and/or DNA-RNA sequences the diagnosis of blastomycosis is only presumptive. A retrospective study of 2007
, reviewing 45 cases of skeletal blastomycosis, reported a median delay in diagnosis of more than 2 months. The delay in diagnosis of the present case was 30 days. In a country “destination of immigration”, Blastomycosis represents a challenge for European paediatricians, and it should be included in the differential diagnosis of unexplained infections in patients coming from endemic areas.
Written informed consent was obtained from the patient’s parents for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Series Editor of this journal.