Case summary: An 8-month-old neutered male domestic shorthair kitten was examined for anorexia, lethargy and palatine ulcers. Systemic lupus erythematosus (SLE) was suspected based on a positive antinuclear antibody (ANA) titer and six manifestations of autoimmunity: fever, paronychia, oral ulcers, proteinuria, thrombocytopenia and leukopenia. Mastocytemia was observed on the blood smear. Although the clinical presentation of this case meets the classification criteria for SLE in humans, tick-borne disease and histopathology evaluation of the oral and cutaneous lesions would have been necessary to support a definite diagnosis of SLE. Baseline ANA titration was performed in two laboratories with conflicting results, which may reflect substrate differences used for the titration, but a false-positive result cannot be excluded. The cat received prednisolone and all clinical and laboratory abnormalities resolved after two months of treatment. Subsequent ANA titers remained positive and were not correlated to the patient's clinical progression.
Relevance and novel information: This report describes new findings associated with a presumptive diagnosis of SLE in a kitten, highlighting that SLE may not be ruled out even in young cats and may be associated with mastocytemia. ANA titration is part of the initial diagnostic work-up of SLE but is a non-specific test and discrepancies can be observed between laboratories. The titration of more specific antibodies such as those used in humans would be helpful to diagnose SLE. ANA titration may not correlate with clinical activity of SLE; hence, the interest of an ANA titer follow-up to establish disease control warrants further investigation.
Keywords: Systemic lupus erythematosus; antinuclear antibodies; mast cells; vasculitis.
© The Author(s) 2020.