Ulcerated and nonulcerated nontuberculous cutaneous mycobacterial granulomas in cats and dogs

Background – Mycobacterial granulomas of the skin and subcutis can be caused by one of a number of pathogens. This review concentrates on noncultivable species that cause diseases characterized by focal granuloma(s), namely leproid granuloma (in dogs) and feline leprosy (in cats). Clinically indistinguishable lesions can be caused by tuberculous organisms (Mycobacterium bovis and Mycobacterium microti) and members of the Mycobacterium avium complex. Rapidly growing mycobacterial species that cause infection of the subcutaneous panniculus associated with draining tracts are not discussed. Disease caused by Mycobacterium ulcerans is an important emerging differential diagnosis for ulcerated cutaneous nodules in certain localized regions. Clinical lesions – Lesions comprise one or multiple nodules in the skin/subcutis. These are generally firm and well circumscribed, and typically become denuded of hair. They may or may not ulcerate, depending on the virulence of the causal organisms and the immune response of the host. Diagnosis – The most inexpensive, noninvasive means of diagnosis is by submission of methanol‐fixed, Romanowsky‐stained smears to a Mycobacterium Reference Laboratory after detecting negatively stained or acid‐fast bacilli on cytological smears. Scrapings of material from slides usually provide sufficient mycobacterial DNA to enable identification of the causal organism using sequence analysis of amplicons after PCR using specific mycobacterial primers. Therapy – Therapy relies upon a combination of marginal resection of easily accessible lesions and treatment using two or three drugs effective against slowly growing mycobacteria, choosing amongst rifampicin, clarithromycin, clofazimine and pradofloxacin/moxifloxacin. Résumé Contexte – Les granulomes mycobactériens cutanés et sous‐cutanés peuvent être causés par un certain nombre d’agents pathogènes. Cette revue se concentre sur les espèces non‐cultivable qui causent des maladies caractérisées par des granulomes focaux, appelés granulomes léproïdes (chez les chiens) et lèpre féline (chez les chats). Les lésions cliniquement indiscernables peuvent être causées par des organismes tuberculeux (Mycobacterium bovis et Mycobacterium microti) et les membres du complexe Mycobacterium avium. Les espèces de mycobactéries à croissance rapide qui causent l’infection du pannicule sous‐cutané associée à des fistules ne sont pas discutées. La maladie causée par Mycobacterium ulcerans est un diagnostic d