ABSTRACT
BACKGROUND: Methylmercury (MeHg) easily crosses the blood-brain barrier and accumulates in the brain. Accumulated MeHg will cause neurological symptoms. We report four pediatric cases of neuropsychological findings with high blood MeHg concentrations. CASE PRESENTATION: Four children were admitted for follow-up study because their total mercury (THg) concentration in the blood was found to be high during a national survey. Case 1 was a 9-year-old female with a 16.6 microg/l blood THg concentration in the survey. During admission, the blood THg, hair THg, and blood MeHg concentration(mercury indices) were 21.4 microg/l, 7.2 microg/g, and 20.1 microg/l, respectively. In our neuropsychological examination, cognitive impairment and attention deficit were observed. Her diet included fish intake 2-3 times per week, and she had been diagnosed with epilepsy at 3 years of age. Case 2 was a 12-year-old male with blood THg of 15.4 microg/l in the survey and the mercury indices were 12.7 microg/l, 5.7 microg/g, and 11.8 microg/l, respectively, on admission. He was also observed to have attention-deficit/hyperactivity disorder. Case 3 was a 10-year-old male child with blood THg of 17.4 microg/l in the survey, and the mercury indices on admission were 21.6 microg/l, 7.5 microg/g and 21.5 microg/l, respectively. In his case, mild attention deficit was observed. Case 4 was a 9-year-old male with blood THg of 20.6 microg/l in the survey and the mercury indices were 18.9 microg/l, 8.3 microg/g, and 14.4 microg/l, respectively, on admission. Mild attention difficulty was observed. CONCLUSION: We suggest that fish consumption may be the main source of MeHg exposure, and that MeHg may have been the cause of the neuropsychological deficits in these cases.