152 Maternal Twins and Male Gender Bias in Autism Spectrum Disorders
concluded. This was not a new idea but was the general view held at that time
by scientists, the medical community, and the public [28].
Soon after the report, several developments changed the paradigm that is
still held as scientific fact. In 1977, Folstein and Rutter [29] published a study
that was based on information collected from same‐sex discordant autistic
twin pairs. The collected data were not founded on a solid scientific basis but
included data from the late Dr M. Carter, records of all children known to the
UK National Society for Autistic Children and a request for cases published in
the society’s newsletter. These efforts resulted in identification of 11 maternal
twins and 10 fraternal twin pairs. Out of the 11 maternal twins, 4 pairs were
found to be concordant. The collected data showed that there was 53% con-
cordance in maternal twin pairs and 0% in fraternal twin pairs. One should be
aware that in today’s rigorous scientific world these data may not have passed
the scrutiny of the Institutional Review Board.
In another study of twins published by Ritvo et al. [30], the authors obtained
data by advertisements placed in the newsletter of the National Society for
Autistic Children (USA). This resulted in 22 concordant out of 23 maternal
twin pairs and 4 out of 17 fraternal pairs for fraternal twins giving a concord-
ance of 98% and 38%, respectively. These data could be skewed since they were
obtained from parents and not from medical doctors [30].
Smalley et al. [31] reviewed the combined results of Folstein and Rutter and
Rivto et al. of 11 maternal twins and 9 fraternal twins. It concluded that mater-
nal twins have concordance of 64% and fraternal twins 9%. An another exten-
sion of the above studies by Bailey et al. [32] found that in the combined sample
60% of maternal pairs were concordant for autism versus 0% of fraternal twins.
From the above summary of information, readers will quickly realize that the
belief currently held in the majority of the scientific community that autism is
a genetic and heritable disease is based on a small number of twin studies. A
thorough inspection of outcomes and claims that support a strong genetic
source of autism reveals incorrect interpretations, methodological biases, and
flawed approximations, not to mention the overstated media reports [1,2].Many Diseases That Were Considered Genetic are
Being Reassessed
On the basis that maternal twin‐pair twins can exhibit genetic differences, one
could hypothesize that disease discordance in maternal twin‐pair twins can
also derive from acquired genetic differences, or varied epigenetic influences.
The discordance for the autosomal dominant disease neurofibromatosis 1
(NF1) in a maternal twin pair has been explained by the presence of an NF1
mutation; the affected twin carried the de novo NF1 mutation in all investi-
gated cells, while the unaffected twin was mosaic [33]. Therefore, one way to