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Background Nocardia cyriacigeorgica , which mainly causes pleuropulmonary and disseminated nocardiosis, has been proved to be one of the most common opportunistic pathogens in patients with immunodeficiency, but the cases that cause subcutaneous abscesses in normal individuals are rare and should be paid attention to. Methods The clinical data of a patient with cutaneous nocardiosis caused by Nocardia cyriacigeorgica in Zhejiang Provincial People’s Hospital were retrospectively analyzed, including clinical manifestations, laboratory examinations, imaging examinations, medication and prognosis. Results Magnetic resonance imaging (MRI) showed that there was a 26 mm × 73 mm abscess under the skin. The pus in the abscess was green. Gram staining showed positive branched rod-shaped and undivided hyphae. After culture, small wrinkle dry white small colonies were observed, and it was identified as Nocardia cyriacigeorgica by MALDI-TOF MS. Conclusion We report the first case of a subcutaneous abscess caused by Nocardia cyriacigeorgica in an immunocompetent patient. Compared with cutaneous nocardiosis of which approximately 80% caused by Nocardia brasiliensis invasion, infection of Nocardia cyriacigeorgica is more insidious and latent, the features of the lesions are also unique. For this Nocardia cyriacigeorgica clinical isolate, the tested antibacterial drugs are generally sensitive and have an ideal prognosis after treatment with linezolid and timely debridement.

BACKGROUND Nocardia pneumonia shares similar imaging and clinical features with pulmonary tuberculosis and lung neoplasms, but the treatment and anti-infective medication are completely different. Here, we report a case of pulmonary nocardiosis caused by Nocardia cyriacigeorgica ( N. cyriacigeorgica ), which was misdiagnosed as community-acquired pneumonia (CAP) with repeated fever. CASE SUMMARY A 55-year-old female was diagnosed with community-acquired pneumonia in the local hospital because of repeated fever and chest pain for two months. After the anti-infection treatment failed in the local hospital, the patient came to our hospital for further treatment. Enhanced computed tomography showed multiple patchy, nodular and strip-shaped high-density shadows in both lungs. A routine haematological examination was performed and showed abnormalities in CD19 + B cells and CD4 + T cells. Positive acid-fast bifurcating filaments and branching gram-positive rods were observed in the bronchoalveolar lavage fluid of the patient under an oil microscope, which was identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry as N. cyriacigeorgica. The patient's condition quickly improved after taking 0.96 g compound sulfamethoxazole tablets three times a day. CONCLUSION The antibiotic treatment of Nocardia pneumonia is different from that of common CAP. Attention should be given to the pathogenic examination results of patients with recurrent fever. Nocardia pneumonia is an opportunistic infection. Patients with CD4 + T-cell deficiency should be aware of Nocardia infection.