Background <p>Chronic manganese (Mn) exposure, particularly in occupational settings such as welding, can lead to Mn-induced parkinsonism, a condition typically considered reversible and distinct from idiopathic Parkinson’s disease (PD). However, the neurotoxic effects of Mn may contribute to or accelerate dopaminergic degeneration in susceptible individuals.</p> Case presentation <p>We report the case of a 53-year-old male welder who initially presented with symmetrical parkinsonism and characteristic T1 hyperintensities in the globus pallidus in Brain MRI, consistent with Mn-induced parkinsonism. Symptoms and Brain MRI abnormalities fully resolved one year after cessation of Mn exposure. Three years later, the patient developed new, progressive, and asymmetric parkinsonian symptoms, including a unilateral resting tremor and bradykinesia. 18- fluoropropyl-2β-carbomethoxy-3β-4-iodophenyl nortropane positron emission tomography imaging demonstrated a marked reduction in striatal dopamine transporter uptake, and the patient responded well to levodopa, confirming the diagnosis of idiopathic PD.</p> Conclusions <p>This case illustrates a rare longitudinal transition from reversible Mn-induced parkinsonism to idiopathic PD, suggesting that prior Mn exposure may act as a precipitating or accelerating factor for PD pathogenesis. Functional neuroimaging is critical for differentiating between these two syndromes. This report underscores the importance of long-term neurological follow-up in patients with occupational Mn exposure and supports the hypothesis that environmental toxins can contribute to neurodegenerative processes.</p>