While genetic factors are recognized as being important in the pathogenesis of autism spectrum disorders (ASD), a role for environmental factors has received considerable attention. Among environmental factors that may be important in the development of ASD, heavy metals, especially mercury, has been examined most often. A porphyrin pattern in urin of patients with ASD may be one of the sign of the heavy metals toxicity. Despite many studies in the field, well controlled studies, including patients with other neurological diseases, are still very rare.
The aim of our study was to determine the levels of heavy metals in blood (zinc, copper, aluminium, lead, mercury), as well as the specific porphyrin levels in the urine of patients with ASD compared with patients with other neurological disorders.
The study was performed in a group of children with ASD (N=52, average age=6,2y) and control group of children with other neurological disorders (N=22, average age=6,6y), matched in terms of intellectual abilities (Mann-Whitney U = 565.0, p = .595). Measurement of heavy metals in blood was performed by atomic absorption spectrometry, while the HPLC method via a fluorescence detector was used to test urinary porphyrin levels. Results were compared across groups using a multivariate analysis of covariance (MANCOVA). In addition a generalized linear model was used to establish the impact of group membership on the blood Cu/Zn ratio.
In term of heavy metals blood levels no significant difference between the groups was found. However, compared to the control group, ASD group had significantly elevated blood Cu/Zn ratio (Wald c2=6.6, df=1, p=.010). Additionaly, no significant difference between the groups was found in term of Uroporphyrin I, Heptacarboxyporphyrin I, Hexacarboxyporphyrin, Pentacarboxyporphyrin I, Coproporphyrin I and Coproporphyrin III level in urine.
The higher Cu/Zn ratio may indicate a decrement in metallothionein system functioning, so we suggest to test blood levels of zinc in all children with ASD and give them a Zn supplement if needed.
See more of: Epidemiology
See more of: Prevalence, Risk factors & Intervention