Abstract

Cutaneous nocardiosis is a rare opportunistic infection of the skin and subcutaneous tissues which may occur as a primary infection or secondarily following dissemination from another site.  Here we report a rare case of cutaneous nocardiosis caused by a potentially novel Nocardia species in a patient who also had nocardia pneumonia. We present the case of a 75-year-old female with a history of left lung transplant due to interstitial lung disease recently treated with anti-thymocyte globulin (ATG) therapy. She presented with weakness and pancytopenia, initially presumed from ATG serum sickness and subsequently treated as sepsis. Imaging showed nodules in the right lower lung, and further workup revealed pneumonia with aspergillus and nocardia species. A detailed physical exam revealed an erythematous, pruritic, non-tender lesion on the right thigh. A punch biopsy of the lesion showed a deep dermal to subcutaneous abscess containing numerous filamentous bacteria morphologically consistent with Nocardia, which stained positive with FITE stain. A culture grew bacteria which were found to most closely resemble the closely related Nocardia species Nocardia coubleae and Nocardia ignorata, but which was only a 98.2% (951/968 bp) match by partial 16S rRNA gene sequencing. For reference, N. coubleae and N. ignorata show 99.4% similarity by this methodology. This case is significant because these findings suggest the possibility of infection with a previously unknown Nocardia species. Furthermore, a search of PubMed returned no case reports of cutaneous nocardiosis caused by either N. ignorata or N. coubleae.