Skeletal cryptococcosis mainly manifests as chronic osteomyelitis, with systemic and local symptoms such as fever, soft tissue swelling and tenderness, and joint dysfunction [4]. Our patient presented with pain and a limited range of motion in the left hip and reported fever during the disease,which was consistent with other cases of cryptococcal osteomyelitis in the literature. The white blood cell count is often normal and the erythrocyte sedimentation rate can be elevated in patients with cryptococcal osteomyelitis [5], and we also confirmed this in this report. However, neither of these results is specific for cryptococcal skeletal infections and could also be indicative of infections in other locations or due to other organisms.
Upon imaging, cryptococcal osteomyelitis generally appears as osteolytic bone destruction, usually without sclerosis or periosteal reaction, destruction of adjacent bone cortex and soft tissue abscesses are often seen [6, 7]. In some cases, the sclerotic margins are also imaged, as well as the sequestrum in the center of the lesion [8, 9]. Pathological fracture is sometimes visible [10, 11]. In our case, cortical bone destruction and soft tissue abscess were evident, but there were no sclerotic margins, sequestrum, and periosteal reaction. This appearance may be related to an early stage of inflammation and the duration of the disease is not long enough. Differential diagnoses that were excluded from our patient included various infectious diseases, such as other fungi, coccidiosis, blastomycosis, actinomyces and mycobacteria. When extensive periosteal reaction occurs, it needs to be differentiated from malignant tumors. There are reports of cryptococcal osteomyelitis cases that had been initially misdiagnosed as Ewing sarcoma or osteosarcoma [12, 13].
Our patient’s history included fever and self-administered cephalosporin antibiotics during her disease. Laboratory results showed elevated C-reactive protein and erythrocyte sedimentation rate, suggesting an inflammatory reaction, and the final pathology confirmed a cryptococcal infection. Hepatic failure is considered being one possible cause of immune insufficiency [14], and hepatitis B virus infection is the major cause of hepatic failure in China. Concomitant chronic hepatitis B with Cryptococcus osteomyelitis has also been reported [5]. The patient in this case had a history of chronic hepatitis B, possibly being associated with the patient's morbidity. The patient’s symptoms improved after a period of antifungal therapy and subsequent fungal culture of secretions tested negative. Follow-up imaging at 11 months showed a reduction in the lesion’s extent and there was no sign of recurrence.
Skeletal cryptococcosis is clinically rare, and its clinical symptoms and imaging findings lack specificity. We propose that cryptococcal osteomyelitis, along with other fungal infections, should be considered as a differential diagnosis in any patient with osteolytic lesions on imaging, Particularly, when patients with immune insufficiency present with infectious osteolytic bone lesions without periosteal reaction.The definitive diagnosis still depends on the histopathology and a fungal culture test. Through timely and accurate diagnosis and active treatment, most patients have a good prognosis.