Dopamine transporter density is decreased in parkinsonian patients with a history of manganese exposure: what does it mean?
Manganese (Mn) exposure can cause parkinsonism. Pathological changes occur mostly in the pallidum and striatum. Two patients with a long history of occupational Mn exposure presented with Mn-induced parkinsonism. In one patient, magnetic resonance imaging (MRI) showed findings consistent with Mn exposure, and Mn concentration was increased in the blood and urine. However, this patient's clinical features were typical of idiopathic Parkinson disease (PD). Previous pathological and positron emission tomography studies indicate that striatal dopamine transporter density is normal in Mn-induced parkinsonism, whereas it is decreased in PD. Therefore, we performed [(123)I]-(1r)-2 beta-carboxymethoxy-3beta-(4-iodophenyl)tropane ([(123)I]-beta-CIT) single-photon emission computed tomography. Severe reduction of striatal beta-CIT binding was indicated, which is consistent with PD. We propose three interpretations: (1) the patients have PD, and Mn exposure is incidental; (2) Mn induces selective degeneration of presynaptic dopaminergic nerve terminals, thereby causing parkinsonism; or (3) Mn exposure acts as a risk of PD in these patients. Our results and careful review of previous studies indicate that the axiom that Mn causes parkinsonism by pallidal lesion may be over-simplified; Mn exposure and parkinsonism may be more complex than previously thought. Further studies are required to elucidate the relationship between Mn and various forms of parkinsonism.
Department of Occupational and Environmental Medicine, University of Ulsan School of Medicine, Ulsan, South Korea.
Y
Y
Kim
J-M
JM
Kim
J-W
JW
Kim
C-I
CI
Yoo
C R
CR
Lee
J H
JH
Lee
H K
HK
Kim
S O
SO
Yang
H K
HK
Chung
D S
DS
Lee
B
B
Jeon
D015984:Causality; D003042:Cocaine / Q000031:analogs & derivatives; D003342:Corpus Striatum / Q000378:metabolism / Q000473:pathology; D003937:Diagnosis, Differential; D004298:Dopamine / Q000378:metabolism*; D050483:Dopamine Plasma Membrane Transport Proteins; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D008345:Manganese / Q000009:adverse effects* / Q000097:blood / Q000652:urine; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins / Q000032:analysis*; D008875:Middle Aged; D009419:Nerve Tissue Proteins; D016273:Occupational Exposure / Q000009:adverse effects*; D010300:Parkinson Disease / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology; D010302:Parkinson Disease, Secondary / Q000139:chemically induced* / Q000000981:diagnostic imaging / Q000473:pathology; D015899:Tomography, Emission-Computed, Single-Photon
D050483:Dopamine Plasma Membrane Transport Proteins; D007457:Iodine Radioisotopes; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D008345:Manganese; C069723:2beta-carbomethoxy-3beta-(4-iodophenyl)tropane; D003042:Cocaine; D004298:Dopamine