Alopecia areata in a spayed pug: Clinical and immunohistochemical findings

A two-year-old spayed female pug presented with symmetrical hyperpigmented alopecic lesions on her axillary and inguinal regions. There were no remarkable findings in dermatologic examinations and hormonal assays. Histological examination of biopsied tissues revealed prominent lymphocytic perifolliculitis along with shrunk hair follicles. Immunohistochemistry for CD3, CD79a, CD4, and CD8 showed a positive stain for CD4 antigen around hair bulbs, suggesting CD4 positive T lymphocyte infiltration. This case suggests the possibility that CD4 T lymphocytemediated inflammatory reaction could be a main mechanism in canine alopecia areata. Additional studies are warranted to investigate the immunological mechanism in canine species.