Progress of non-motor symptoms in early-onset Parkinson's disease

Parkinson's disease (PD) is a common degenerative disease of the central nervous system that is characterized by movement disorders and non-motor symptoms (NMSs). The associated NMSs primarily include neuropsychiatric symptoms, autonomic dysfunction, sleep-wake disorders, pain, fatigue, and hyposmia. These NMSs can occur at any stage of PD, especially before the onset of motor symptoms, and may affect a patient's quality of life more than motor symptoms. Although PD is most commonly diagnosed in people over 65 years, some patients exhibit symptom onset before the age of 50, which is clinically known as early-onset Parkinson's disease (EOPD). The high heterogeneity and incidence of EOPD-associated NMSs can lead to the misdiagnosis of EOPD as other neurodegenerative diseases. In this review, we discuss the research progress related to NMSs in patients with EOPD, focusing on neuropsychiatric disorders, autonomic dysfunction, sleep disorders, and sensory impairment, and outline the association of NMSs with different genotypic alterations, with the aim of providing assistance in the clinical management of patients.