Panniculitis, due to Mycobacterium smegmatis, in two Finnish cats

Pyogranulomatous panniculitis due to infection by Mycobacterium smegmatis was diagnosed in two cats in Finland, a country with a rather cold climate. The diagnosis was confirmed by sequencing of the 16S rRNA gene, which gave a perfect match with the M smegmatis strain ATCC 19420. Gene sequencing makes it possible to distinguish M smegmatis from closely related mycobacteria such as M goodii sp.nov. Diagnosing this entity seems to be a question of having a high index of suspicion. The appearance of the disease as well as sampling is described in detail. In our first case an initial erroneous diagnosis of Nocardia species considerably delayed our arriving at the right diagnosis. The first patient has now been followed for more than 7 years. Her disease is chronic, but she is not systemically affected. Several antimicrobials were tried. Probable side effects of enrofloxacin medication are described.