Co-occurrence of parkinson disease and multiple sclerosis - a critical note

Area of Science:

• Neurology
• Neuroimmunology
• Genetics

Background:

• Multiple sclerosis (MS) commonly presents with movement disorders like tremor and ataxia.
• The co-occurrence of MS with parkinsonism, and specifically Parkinson disease (PD), is exceptionally rare.
• Existing theories on MS and PD co-occurrence range from coincidence to causality, lacking systematic evaluation.

Purpose of the Study:

• To investigate the prevalence, characteristics, and causal relationships between MS and PD.
• To explore potential shared genetic and pathogenic mechanisms underlying the co-occurrence of MS and PD.
• To critically assess the evidence for a causal link between demyelinating lesions and parkinsonism.

Main Methods:

• Systematic review of reported cases of MS and PD co-occurrence.
• Analysis of genetic studies investigating shared genes (e.g., LRRK2, PINK1, BACE2, CD69) in MS and PD.
• Examination of pathological findings, including iron accumulation in the substantia nigra.

Main Results:

• While demyelinating lesions can cause parkinsonism in MS, some cases involve PD and MS as distinct coexisting diseases.
• The presence of MS in LRRK2-associated PD suggests a role for immune function in both conditions.
• Shared genetic factors and iron accumulation in the substantia nigra are potential common pathways.

Conclusions:

• The co-occurrence of MS and PD, though rare, warrants critical consideration due to potential shared etiological factors.
• Immune dysregulation and specific genetic predispositions may contribute to both MS and PD.
• Further research is essential to elucidate the complex interplay and causal relationships between these neurological diseases.