Nocardia infection: a rare case report of a cerebellar mass

Central nervous system (CNS) nocardiosis is a rare but lethal opportunistic infection, presenting a formidable diagnostic and therapeutic challenge, especially in immunocompromised populations. The most common presentation is a cerebral abscess.

We report the case of a 53-year-old male with a history of relapsed and refractory multiple myeloma who presented with an acute change in mental status and ataxia. Initial clinical suspicion centered on a posterior circulation ischemic event. However, magnetic resonance imaging (MRI) revealed a large, rim-enhancing cerebellar mass with associated obstructive hydrocephalus. The patient underwent surgical excision of the lesion, and subsequent microbiological culture confirmed an abscess caused by a Nocardia species. He was treated with a prolonged course of targeted antimicrobial therapy, including intravenous imipenem, followed by oral linezolid and trimethoprim-sulfamethoxazole. At the 3-month outpatient follow-up after discharge, the patient was found to have thrombocytopenia, attributed to the side effects of oral trimethoprim-sulfamethoxazole. Treatment was subsequently maintained with oral linezolid 600 mg for 1 year. Despite improvement of the abscesses, the patient ultimately succumbed to the progression of his long-standing multiple myeloma.

This case underscores the importance of including uncommon opportunistic pathogens like Nocardia in the differential diagnosis of CNS lesions in immunocompromised patients. A definitive diagnosis via microbiological analysis of tissue specimens is imperative to guide appropriate antimicrobial therapy and achieve a favourable clinical outcome.