First identification of a single amino acid change in the spike protein region of feline coronavirus detected from a coronavirus-associated cutaneous nodule in a cat

Osumi, Takafumi; Mitsui, Ikki; Leutenegger, Christian M; Okabe, Ryo; Ide, Kaori; Nishifuji, Koji

Here, we successfully obtained genetic evidence of a FCoV genotype that is commonly associated with FIP development in a cutaneous nodule. The histopathological and immunohistochemical findings also suggest coronavirus infection. 11, 12 These findings support a diagnosis of FIP, despite the absence of uveitis or ascites, which are commonly seen in cats with effusive or non-effusive FIP. Fever and hyperglobulinaemia with polyclonal gammopathy are suggestive of FIP. Hepatic nodules and anaemia are occasionally recognised in cats with noneffusive FIP, but FCoV was not identified in the hepatic nodules of the present case. Based on our collective histopathological and immunohistochemical findings, along with molecular diagnostics and high titre of serum anti-FCoV antibodies, we suspected that the present case had a predominantly cutaneous type of non-effusive FIP that has not previously been described in the literature. As the present case had upper respiratory signs and stomatitis, concurrent FHV or FCV infections were also considered; however, we did not investigate those viruses because the nodular dermatitis with histopathology of pyogranulomatous inflammation did not strongly support the diagnoses.