Front Matter

Myth of the Genetic Origin of Autism 71

The name Fragile X syndrome derives from a defective portion of the X chro-
mosome that looks fragile and squeezed together under a microscope. It results
from the mutation of one single gene and turns the gene off. Some individuals
experience just a mutation and do not display symptoms; others have much
more serious symptoms due to a larger mutation. About one‐third of children
with Fragile X syndrome also meet ASD criteria, similar to individuals with
Down syndrome who have extra pieces of chromosome 21. Conversely, about 1
in 25 ASD‐diagnosed children have experienced the same mutation that under-
lies development of Fragile X syndrome. We maintain that Fragile X syndrome is
inherited, a widely accepted position, but that ASD is largely due to environmen-
tal factors, arising from exposure to synthetic chemicals during gestation [58].

Tuberous Sclerosis

A rarely occurring genetic malady, tuberous sclerosis afflicts vital organs,
including the brain, with noncancerous tumors (Figure  2.3). About 2 million

Brain:

Heart:

∙ 90% Epilepsy

∙ 80–90% SEN

∙ 10–15% SEGA

∙ 90% TAND

∙ 90% cardiac rhabomyoma

Adults

∙ 20% cardiac rhabomyoma

Infants

Other:

∙ 50% oral fibromas

∙ 50% retinal astrocytic

hamartomas

Lung:

Women

∙ 80% asymptomatic LAM

∙ 10% MMPH

∙ 5 –10% symptomatic

LAM, can lead to

respiratory failure

Men and Women

Skin:

∙ 75% angiofibroma

∙ >50% shagreen patches

∙ 90% focal hypopigmen-

tation

∙ 20–30% ungual fibroma

∙ 25% fibrous cephalic

plaques

Kidney:

∙ 70% angiomyolipoma

∙ 35% simple multiple cysts

∙ 5% polycystic kindly

disease

∙ 2–3% renal cell carcinoma

∙ 50% intellectual disability

∙ 40% autism spectrum

Figure 2.3 Key features of tuberous sclerosis. Source: Adapted from https://www.nature.
com/articles/nrdp201635. Reproduced with permission of Springer Nature.