Significance of mastocytemia in cats

New findings associated with presumptive systemic lupus erythematosus in a kitten

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.

Abnormal Sysmex XT-2000iV DIFF scattergram in a cat with a prominent mastocytemia

A 2-year-old neutered male domestic shorthair cat was presented to the emergency service of the National Veterinary School of Toulouse (France) for acute vomiting and diarrhea with lethargy, inappetence, and adypsia for the past 48 hours. Complete blood counts were performed with the ProCyte DX at the emergency department and with the Sysmex XT-2000iV at the laboratory 2 weeks later. The scattergrams from the two analyzers revealed similar unusual and abnormal dot plots. The Sysmex XT-2000iV DIFF scattergram also showed no clear separation between different leukocyte populations. The eosinophil cluster was in an abnormal location compared with that of the "typical" location in a normal cat. A blood smear evaluation revealed the presence of numerous mast cells. Thus, we hypothesized that the Sysmex XT-2000iV had detected the mast cell population, and this led to errors in the differential counts. To explore this hypothesis, we manually gated on the DIFF scattergram and performed a manual differential on the blood smear. With this new gating strategy, the Sysmex XT-2000iV and manual differentials were similar. Thus, in the case of systemic mastocytosis, mast cells can be located between the lymphocyte, monocyte, and eosinophil clusters on scattergrams.

Rapid preparation and single-cell analysis of concentrated blood smears using a high-throughput blood cell separator and a microfabricated grid film

Cytological examination of peripheral white blood cells inhomogeneously distributed on a blood smear is currently limited by the low abundance and random sampling of the target cells. To address the challenges, we present a new approach to prepare and analyze concentrated blood smears by rapidly enriching white blood cells up to 32-fold with 92% recovery on average at a high throughput (1mL/min) using a deterministic migration-based separator and by systematically analyzing a large number of the cells distributed over a blood slide using a microfabricated grid film. We anticipate that our approach will improve the clinical utility of blood smear tests, while offering the capability to detect rare cell populations.

Concurrent multiple myeloma and mast cell neoplasia in a 13-year-old castrated male Maine Coon cat

A 13-year-old, castrated male Maine Coon cat was presented to Oklahoma State University Boren Veterinary Medical Teaching Hospital for yearly echocardiographic examination monitoring hypertrophic cardiomyopathy (HCM) diagnosed in 2003. Physical examination revealed a heart murmur and premature beats, likely related to HCM, but was otherwise unremarkable. A biochemistry profile revealed a hyperglobulinemia (6.3 g/dL). Cytologic examination of fine-needle aspirates from liver and spleen revealed increased numbers of plasma cells and mast cells, confirmed with subsequent histologic examination. Immunohistochemistry (IHC) for c-kit in the spleen and liver showed mast cells predominantly exhibiting type I staining pattern, with moderate numbers exhibiting type II pattern in spleen, and scattered cells exhibiting type II and III patterns in liver. Bone marrow cytology and core biopsy documented approximately 22% plasma cells. Cutaneous masses on the cat's left shoulder and right carpus were cytologically confirmed mast cell tumors. Serum protein electrophoresis with immunofixation confirmed an IgG monoclonal gammopathy. This is an example of 2 hematologic neoplasms occurring simultaneously in a cat. Concurrent pathologies may be overlooked if a single disease is diagnosed and suspected of causing all clinical signs. Both neoplasms were well differentiated, and neoplastic cells could have easily been interpreted as a reactive population had a full workup not been performed. Missing either diagnosis could result in a potentially lethal outcome. Eleven months after diagnoses, the cat was clinically doing well following a splenectomy and oral prednisolone and chlorambucil chemotherapy. Globulins decreased to 4.9 g/dL.