Manganism

Manganism is a neurotoxic disorder caused by long-term inhalation of manganese compounds, most often in workers exposed to manganese dust or fumes. Industries at risk include mining, smelting, welding, manganese alloy production, cement, and battery manufacture. The syndrome reflects manganese accumulation in the brain, particularly in the basal ganglia.

Pathophysiology: Manganese concentrates in the basal ganglia, especially the globus pallidus, where it disrupts dopaminergic transmission and other neurotransmitter systems, potentially impairing mitochondrial function.

Clinical features: The onset is insidious after years of exposure. Manganism commonly resembles a parkinsonian syndrome but differs from idiopathic Parkinson’s disease in being less responsive to levodopa, with prominent dystonia, gait and postural disturbances, and facial involvement. Tremor, when present, is usually less prominent. Psychiatric symptoms and cognitive slowing can occur; dysarthria and dysphagia may develop.

Diagnosis: Diagnosis combines exposure history, neurologic findings, and imaging. MRI often shows bilateral T1-weighted hyperintensity in the globus pallidus. Blood manganese levels do not reliably reflect brain burden and are not diagnostic.

Management and prognosis: The primary intervention is removal from exposure. Chelation with calcium disodium EDTA (CaNa2EDTA) has been used in some cases, but evidence is limited. Levodopa may provide partial benefit in some patients. Rehabilitation and supportive care are important, and the course is often progressive, though early exposure cessation can improve outcomes.