GBA1 and Parkinson disease: In contrast to autosomal recessive forms of PD (caused by homozygous mutations in PARK2, PINK1, or DJ‐1) and autosomal dominant forms of PD (caused by heterozygous mutations in alpha‐synuclein (SNCA) or leucine‐rich repeat kinase 2), PD‐GBA1 supports both autosomal recessive and autosomal dominant modes of inheritance (Sidransky 2012).