LRRK1 and early-onset autosomal dominant Alzheimer disease: However, LRRK1 has rarely been reported to be associated with a human disease except that one family was found to carry LRRK1 mutations linked to the osteosclerotic metaphyseal dysplasia (OSMD) [22], while LRRK2 has been strongly associated with PD, Alzheimer’s disease (AD), and immune disorders [23,24].