SCA15 is a cerebellar ataxia characterized by postural tremor, hyperreflexia, dysarthria and scanning speech, as well as gait, limb and truncal ataxia. Ocular anomalies include dysmetric saccades, impaired smooth pursuits and horizontal, gaze-evoked nystagmus. Affected individuals exhibit cerebellar atrophy mainly affecting the vermis.  The disease has a wide range of onset, affecting people between the ages of 10 and 50 years. It has a very slow progression and most patients remain ambulatory.

The disorder follows an autosomal dominant pattern of inheritance and is caused by heterozygous mutations in the ITPR1 gene. The gene encodes an intracellular ion channel that mediates the release of calcium from the endoplasmic reticulum upon stimulation by its ligand, inositol 1,4,5-triphosphate. Mutations in the gene associated with SCA15 include missense variants and large deletions. Recent studies have also found homozygous ITPR1 mutations in SCA15 affected individuals.