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As an example, mutations in the LRRK2 gene can cause autosomal dominant Parkinson disease. However, the age of onset of Parkinson's in people with LRRK2 gene alterations is highly variable (from 35-years to 78-years). Symptom and symptom severity can also vary, even between family members. Also, some people with LRRK2 gene alterations never develop Parkinson disease at all.
Alterations in LRRK2 is only one example of a cause of familial Parkinson disease. In addition to LRRK2, SNCA gene alterations can cause autosomal dominant Parkinson disease. Alterations in the genes PARK7 or PINK1 can cause an