Pulmonary Nocardia concava infection in a patient with mantle cell lymphoma receiving bortezomib and rituximab

A 75-year-old man presented to our hospital with a high fever, 39·5°C. 8 months previously, he had visited the haematology clinic for generalised lymphadenopathy. Whole body CT showed enlarged axillary and abdominal lymph nodes and splenomegaly, and a bone marrow biopsy showed lymphoma cell infiltration. He was diagnosed with metastatic mantle cell lymphoma and treated with rituximab and bortezomib. Treatment regimen consisted of rituximab 375 mg/m2 intravenously on day 1 and bortezomib 1·3 mg/m2 intravenously on days 1, 4, 8, and 11 for the first course in month 1, followed by five more courses with the same schedule for the next 5 months. At the end of treatment, CT showed that the lymphadenopathy had disappeared, and the lymphoma was in remission. 3 days before this scan, the patient developed a high fever (39·5°C). Blood tests showed an elevated white blood cell count (19 400 per μL vs 3300–8600 per μL expected range), with neutrophil predominance (95% vs 38·3–71·1% expected range) and high concentration of C-reactive protein (19·2 mg/dL vs <0·15 mg/dL expected range). Chest CT showed multiple nodules with bilateral pulmonary infiltrates (figure). Gram staining and modified Ziehl-Neelsen staining of the sputum showed branching gram-positive filaments. 16S rRNA gene sequencing identified the presence of a microorganism. A Basic Local Alignment Search Tool (BLAST) search of the GenBank database showed that the sequence was most similar to that of Nocardia concava type strains IFM 0576 and IFM 0354 (99% identity). On the basis of these results, the patient was diagnosed with pulmonary nocardiosis. Antibiotic susceptibility testing showed that the isolate was sensitive to minocycline and co-trimoxazole. Because the patient had a history of co-trimoxazole-induced renal dysfunction, he was treated with minocycline (100 mg twice a day orally), and his symptoms improved. Chest CT 4 months after initial CT showed disappearance of the pulmonary nodules. Minocycline was discontinued 1 year later, and he has not relapsed for 5 years to date.