Idiopathic multifocal calcinosis cutis presenting in a cat with vestibular syndrome: clinical, radiographic and histopathological findings

Case summary: A 2-year-old spayed female British Shorthair cat was presented with an acute onset of right-sided head tilt, circling and horizontal nystagmus. Neurological examination, CT and video-otoscopic evaluation confirmed a right-sided peripheral vestibular syndrome secondary to otitis media. The cat received cefixime (10 mg/kg PO q24h) and methylprednisolone (1 mg/kg PO q24h) for 2 weeks, resulting in marked improvement of vestibular signs by day 4. During the physical examination, multiple firm, non-painful subcutaneous nodules of varying sizes were palpated in different body regions, unrelated to the primary neurological complaint. Laboratory analysis revealed serum calcium, ionised calcium and phosphorus concentrations within reference intervals, with a calcium-phosphorus product below the threshold for metastatic calcification. Ultrasonographic and hormonal assessments excluded metabolic, iatrogenic and dystrophic causes. Histopathological examination of an excisional biopsy from the largest lesion revealed dermal collagen fibril calcification surrounded by a hypocellular fibrous capsule and mild lymphohistiocytic inflammation, consistent with calcinosis cutis. Relevance and novel information: The clinical, laboratory and histopathological findings supported a diagnosis of multifocal idiopathic calcinosis cutis. To the authors' knowledge, this is the first report from Türkiye describing multifocal subcutaneous idiopathic calcinosis cutis in a cat. This case emphasises the importance of thorough physical examinations to detect concurrent, clinically silent dermatological conditions during neurological evaluations.