A Familial History of Pink Disease Identified As a Risk Factor for Autism Spectrum Disorders

Background: The aetiology of Autism Spectrum Disorders (ASD) remains a mystery, although contemporary research points to a combination of genetic and environmental factors. Controversially, exposure to toxic substances, particularly mercury, has been postulated as a possible environmental trigger in the development of an ASD. Historically, the pervasive use of mercury in medicinal products is well documented, including the consequences of its use, such as the case of Pink Disease, or infantile acrodynia, which was especially prevalent in the first half of the 20th century. Primarily attributed to exposure to mercury commonly found in teething powders, approximately 1 in 500 exposed children developed the condition. The differential risk factor was identified to be an idiosyncratic sensitivity to mercury. Analogous to the Pink Disease experience, if mercury is a potential environmental trigger of ASD, a sensitivity to mercury may also be present in children with an ASD.

Objectives: The objective of the present study is to determine whether a diagnosis of ASD is more prevalent among children with a familial history of Pink Disease (mercury sensitivity) in comparison to a comparable general population prevalence.

Methods: To test this objective, Pink Disease survivors were surveyed to ascertain the health outcomes of their descendants. The survey included sociodemographic questions regarding the Pink Disease survivor, and information pertaining to the Pink Disease survivor’s children and grandchildren. For each descendant, the survivor was asked to provide their gender and date-of-birth, and whether they had been diagnosed with any of the following conditions prior to the age of 16 years: autism, Asperger’s, attention deficit hyperactivity disorder, epilepsy, Fragile X, and/or Down Syndrome. Participants were recruited via the Australian Pink Disease Support Group (a not-for-profit group dedicated to providing support and information to Pink Disease survivors and their families – the only such group in the world). In order to minimize response bias, the true purpose of the study was not included on recruitment materials sent out to potential participants; instead, the materials indicated that the purpose of the study was to investigate the general health outcomes of the descendants of Pink Disease survivors. Five hundred and twenty-two participants completed the survey which gathered health data on 1366 grandchildren. The prevalence rates for each of the listed conditions was calculated and compared to well-established general population prevalence rates. Only live births, biological children, and children surviving to at least 5 years-of-age were included in the analysis. 

Results: The results showed that the prevalence rate of ASD among the grandchildren of Pink Disease survivors (1 in 25) was significantly higher than the general population prevalence rate (1 in 160) of the same birth year cohort. There were no significant differences in prevalence rates among for any of the non-ASD conditions. 

Conclusions: The results support the hypothesis that mercury sensitivity may be a heritable/genetic risk factor for ASD.