Introduction
The most common clinical signs of paraneoplastic syndromes in horses
include hypercalcemia, hypoglycemia, cachexia, intermittent fever,
anemia, thrombocytopenia, neutrophilia, protein losing enteropathy,
vasculitis and pruritus (Axiak and Johnson 2011, Knottenbelt et al.
2015). Long before the tumour is clearly identified, paraneoplastic
pruritus is often the main or only clinical sign observed, which can
make early and accurate disgnosis of such pathologies very difficult.
(Knottenbelt et al. 2015). Such pruritus can be accompanied by alopecia,
which can be as a consequence of paraneoplastic changes or by
self-mutilation (Knottenbelt et al. 2015). Skin biopsies and scrapings
are often inconclusive or nonspecific and can be confused with the
consequences of self-trauma (Knottenbelt et al. 2015). There is some
evidence that pruritus as a consequence of neoplasia is caused by the
destruction of T-cells arising from pathological cytokines produced by
the tumour itself or the tumour’s growth, nerve compression, bile duct
compression with cholestasis or necrotic tumourous cells (Knottenbelt et
al. 2015). Paraneoplastic pruritus has been described in horses with
lymphoma (Finley et al. 1998), mast cell tumours (Combarros et al. 2020)
and renal carcinomas (Curnow 2020).
Despite the fact that pruritus is reported as one of the relatively more
common equine paraneoplastic clinical signs, there is a little clinical
evidence to support it.
In this article, we would like to document a case whereby persistent
pruritus was the only clinical sign in a horse suffering from
paraneoplastic pruritus caused by malignant round cell tumours.
Publications in equine oncology are few, and documentation of such cases
such are necessary to aid and assist practitioners in achieving more
expediated and correct diagnosis of such conditions