Similar to PD, AD comes in two forms: familial and sporadic, with approximately 1% of cases associated with familial autosomal dominant mutations in the genes encoding for amyloid beta protein precursor (AβPP) or presenilin 1 or 2 (PS1 or PS2), which are directly involved in AβPP processing [184]. The gene discussed is PSEN1; the disease is Alzheimer disease.