Concurrent infection with Cryptococcus neoformans/gattii species complex and Mycobacterium avium affecting the subcutis and bone of a pelvic limb in a cat

Abstract

This paper describes a cat with severe localised infections with Cryptococcus neoformans/gattii species complex and Mycobacterium avium affecting the subcutis and underlying fascia and bone of the right pelvic limb. The simultaneous isolation of both pathogens in this patient was unexpected and posed unique issues concerning both diagnosis and clinical management. The aetiopathogenesis of this infection is discussed in relation to aspects of diagnosis and therapy.

Fig 1.

‘Non-healing wound’ of the craniomedial aspect of the right pelvic limb. The appearance of the lesion is reminiscent of the ‘non-healing wounds' associated with rapidly growing mycobacteria such as M smegmatis.

Fig 2.

Note the generalised soft tissue swelling on both the lateral and medial aspects of the stifle and gas in the soft tissue planes. The medial third of the tibial condyle is no longer present. There is a ragged medial margin of bone adjacent to some more medially located opacities which may represent residual bone. Within the proximal tibia itself, there is a heterogenous mixture of increased and decreased bone opacity which has an unstructured appearance and it suggests a reactive bone change within the cancellous compartment of the proximal tibia (arrows). The periosteum appears normal.

Fig 3.

Cytology (Ziehl—Neelsen stain) of the lesion demonstrating acid-fast bacilli (small arrow) and capsulated cryptococcal blastoconidia (large arrow).