感染源が不明であった深在性真菌症による頭蓋底骨髄炎例

抄録

Skull base osteomyelitis is an extremely rare disease that usually occurs by direct spread of bacterial or fungal infection from adjacent organ, such as the paranasal sinus or external ear canal. However, some cases without a clear primary focus of infection, such as paranasal sinusitis or malignant otitis externa, have also been reported. In such cases, definitive diagnosis is difficult. We encountered a case of skull base osteomyelitis caused by fungal invasion that spread from the nasopharynx to the skull base, in which the original focus of infection remained unclear.

A 76-year-old man with a history of diabetes mellitus was referred to our hospital with left otalgia and headache. CT examination showed bone erosion of the skull base and slight swelling of the nasopharynx. A biopsy specimen obtained from the nasopharynx revealed inflammation, but no evidence of malignancy. PCR for tuberculosis and bacterial or fungal culture of the collected tissues were negative. Serum β-D glucan was negative. Amoxycillin hydrate was prescribed as empiric therapy. While the headache and left otalgia improved transiently, the patient complained of severe headache again while the antibiotic therapy was still ongoing. In addition, he developed hoarseness caused by left vocal cord paralysis. A repeat serum test at this time revealed a positive result for β-D glucan. We prescribed liposomal amphotericin B, an antifungal agent, and the headache resolved. We made the clinical diagnosis of skull base osteomyelitis caused by invasive fungal infection.

When bone erosion of the skull base with swelling around it is observed, it is important to rule out skull base osteomyelitis caused by fungal infection, besides malignant tumor. Moreover, in some cases, empiric therapy with an antifungal agent(s) is needed despite the absence of pathological or microbiological evidence of fungal infection.