First Reported Human Case of Primary Lymphocutaneous Nocardiosis Caused by Nocardia shinanonensis

Nocardia species are ubiquitous environmental microorganisms that can cause localized cutaneous, pulmonary or disseminated infections in humans. Primary cutaneous nocardiosis is uncommon and may present as cellulitis, abscesses, ulcers, granulomas or lymphocutaneous disease characterised by nodular lesions distributed along lymphatic pathways. The species most frequently associated with cutaneous nocardiosis is Nocardia brasiliensis; however, the number of newly recognised pathogenic species isolated from clinical samples has increased in recent years. This report describes the first reported case of primary lymphocutaneous nocardiosis caused by Nocardia shinanonensis in a 36-year-old immunocompetent woman with involvement of the left upper limb. The causative agent was identified by bacteriological culture, matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF), and 16S rRNA gene sequencing. The patient was successfully treated with oral trimethoprim–sulfamethoxazole for 12 weeks, with complete clinical resolution and residual hypertrophic scarring. This case expands the spectrum of human infections caused by N. shinanonensis and highlights the importance of molecular tools for accurate species-level identification of rare nocardial pathogens.