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We have read with interest the article “Association of dopamine transporter and monoamine oxidase molecular polymorphisms with sudden infant death syndrome and stillbirth: new insights into the serotonin hypothesis” by Filonzi et al. in a recent edition of Neurogenetics . The authors have presented a study on two polymorphisms, one of those a functional length polymorphism in the promoter region of the monoamineoxidase A (MAOA) gene, in 20 cases of sudden infant death syndrome (SIDS) and five cases of stillbirth compared to healthy controls. The main conclusion from the paper seems to be that MAOA allele 4R (with increased transcriptional activity) is significantly more common in SIDS than in controls.
There are, however, severe concerns that this conclusion could be incorrect:
Therefore, in order to check the results by Filonzi et al. in an independent study, we typed the MAOA locus using PCR with fluorescence-labeled primers and capillary electrophoresis in small cohorts of 22 male and 21 female SIDS cases and 20 male and 21 female controls.
In contrary to the findings of Filonzi et al., we found a – however, statistically insignificant – trend towards a lower incidence of allele 4 in male, but not in female SIDS cases (Table 1).
We thus conclude that a potential association of SIDS and MAOA promoter polymorphism is worth to be further studied in a larger sample but that the conclusions drawn in the study by Filonzi et al. might very well be misleading. The X-chromosomal location of this polymorphism is most intriguing, as there is a male preponderance in SIDS and linkage to an X-chromosomal locus might be an explanation for this phenomenon .
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