In addition to providing a general overview of the clinical and paraclinical features and summarizing the current knowledge on the pathophysiology of this new disorder, we here specifically point to the association of serum ITPR1-IgG/anti-Sj with dementia and psychosis by reporting on a patient in whom these antibodies were associated with rapidly progressive, severe cognitive decline, mainly affecting memory, attention and executive functions, optic hallucinations and depression. The gene discussed is ITPR1; the disease is Mental deterioration.