: Neuronal intranuclear inclusion disease is a rare hereditary neurodegenerative disease characterized by localized eosinophilic intracytoplasmic inclusion bodies in cells of the nervous system and internal organs. This disorder is frequently missed or misdiagnosed, as there is significant heterogeneity of its clinical presentation. Recently, genetic sequencing has revealed complex links between neuronal intranuclear inclusion disease and other neurodegenerative diseases, potentially explaining the diversity of clinical manifestations. Herein, we describe the case of a 68-year-old male Chinese patient who was initially diagnosed with Parkinson's disease based on classic symptomatology and ¹²³I-metaiodobenzylguanidine scintigraphy results and was subsequently treated with oral methyldopa for 3 years. He developed a paroxysmal tic before he presented to our hospital for treatment after a convulsive seizure. Brain magnetic resonance imaging identified signal hyperintensity at the corticomedullary junction on diffusion-weighted imaging. Skin biopsy results and genetic testing confirmed a revised diagnosis of neuronal intranuclear inclusion disease. This report highlights that patients clinically diagnosed with Parkinson's disease may actually be in the early stages of neuronal intranuclear inclusion disease, suggesting that patients with suspected Parkinson's disease should also be screened for this disease.