Phenotypic commonalities in familial and sporadic Parkinson disease.

BACKGROUND Parkinson disease (PD) is a clinically well-documented neurodegenerative disorder. However, the mechanism or mechanisms of its phenotypic expressions are still unknown. OBJECTIVE To compare phenotypes by examining demographic and clinical features of patients with familial PD and sporadic PD and with or without a family history of PD. DESIGN Historical review of patients with sporadic PD in clinic-based samples and individual patients diagnosed with PD from families whose linkage to mutations or loci has been identified. SETTING Movement disorder clinic in a referral center. PATIENTS A total of 1277 patients with sporadic PD and 40 patients with familial PD. MAIN OUTCOME MEASURES Clinical features, including distribution by sex, initial motor symptom, location of initial motor symptom, and frequency of asymmetric motor symptoms. RESULTS Despite different etiologic backgrounds, both familial and sporadic PD exhibited several interesting commonalities, including a higher incidence in men, tremor as the initial motor symptom (predominantly involving the upper extremities), and asymmetric parkinsonism during disease course. CONCLUSIONS The increased incidence of parkinsonism in men with familial PD suggests that the sex disparity is more likely the result of a protective effect against development of PD in women than of an increased risk in men that is associated with environmental factors. Phenotypic similarity among familial and sporadic PD indicates that a similar topographic distribution of the nigrostriatal lesion exists in patients with either form of PD regardless of apparent genetic influence.