Table A:
Summary Comparison of Characteristics
of Autism & Mercury Poisoning

Mercury Poisoning

Autism

Psychiatric Disturbances

 

Social deficits, shyness, social withdrawal

Social deficits, social withdrawal, shyness

Depression, mood swings; mask face

Depressive traits, mood swings; flat affect

Anxiety

Anxiety

Schizoid tendencies, OCD traits

Schizophrenic & OCD traits; repetitiveness

Lacks eye contact, hesitant to engage others

Lack of eye contact, avoids conversation

Irrational fears

Irrational fears

Irritability, aggression, temper tantrums

Irritability, aggression, temper tantrums

Impaired face recognition

Impaired face recognition

Speech, Language & Hearing Deficits

 

Loss of speech, failure to develop speech

Delayed language, failure to develop speech

Dysarthria; articulation problems

Dysarthria; articulation problems

Speech comprehension deficits

Speech comprehension deficits

Verbalizing & word retrieval problems

Echolalia; word use & pragmatic errors

Sound sensitivity

Sound sensitivity

Hearing loss; deafness in very high doses

Mild to profound hearing loss

Poor performance on language IQ tests

Poor performance on verbal IQ tests

Sensory Abnormalities</TD< tr>

 

Abnormal sensation in mouth & extremities

Abnormal sensation in mouth & extremities

Sound sensitivity

Sound sensitivity

Abnormal touch sensations; touch aversion

Abnormal touch sensations; touch aversion

Vestibular abnormalities

Vestibular abnormalities

Motor Disorders

 

Involuntary jerking movements - arm flapping, ankle jerks, myoclonal jerks, choreiform movements, circling, rocking

Stereotyped movements - arm flapping, jumping, circling, spinning, rocking; myoclonal jerks; choreiform movements

Deficits in eye-hand coordination; limb apraxia; intention tremors

Poor eye-hand coordination; limb apraxia; problems with intentional movements

Gait impairment; ataxia - from incoordination & clumsiness to inability to walk, stand, or sit; loss of motor control

Abnormal gait and posture, clumsiness and incoordination; difficulties sitting, lying, crawling, and walking

Difficulty in chewing or swallowing

Difficulty chewing or swallowing

Unusual postures; toe walking

Unusual postures; toe walking

Cognitive Impairments

 

Borderline intelligence, mental retardation - some cases reversible

Borderline intelligence, mental retardation - sometimes "recovered"

Poor concentration, attention, response inhibition

Poor concentration, attention, shifting attention

Uneven performance on IQ subtests

Uneven performance on IQ subtests

Verbal IQ higher than performance IQ

Verbal IQ higher than performance IQ

Poor short term, verbal, & auditory memory

Poor short term, auditory & verbal memory

Poor visual and perceptual motor skills, impairment in simple reaction time

Poor visual and perceptual motor skills, lower performance on timed tests

Difficulty carrying out complex commands

Difficulty carrying out multiple commands

Word-comprehension difficulties

Word-comprehension difficulties

Deficits in understanding abstract ideas & symbolism; degeneration of higher mental powers

Deficits in abstract thinking & symbolism, understanding other’s mental states, sequencing, planning & organizing

Unusual Behaviors

 

Stereotyped sniffing (rats)

Stereotyped, repetitive behaviors

ADHD traits

ADHD traits

Agitation, unprovoked crying, grimacing, staring spells

Agitation, unprovoked crying, grimacing, staring spells

Sleep difficulties

Sleep difficulties

Eating disorders, feeding problems

Eating disorders, feeding problems

Self injurious behavior, e.g. head banging

Self injurious behavior, e.g. head banging

Visual Impairments

 

Poor eye contact, impaired visual fixation

Poor eye contact, problems in joint attention

“Visual impairments,” blindness, near-sightedness, decreased visual acuity

“Visual impairments”; inaccurate/slow saccades; decreased rod functioning

Light sensitivity, photophobia

Over-sensitivity to light

Blurred or hazy vision

Blurred vision

Constricted visual fields

Not described

Physical Disturbances

 

 

 

Increase in cerebral palsy; hyper- or hypo-tonia; abnormal reflexes; decreased muscle strength, especially upper body; incontinence; problems chewing, swallowing, salivating

Increase in cerebral palsy; hyper- or hypotonia; decreased muscle strength, especially upper body; incontinence; problems chewing and swallowing

Rashes, dermatitis/dry skin, itching; burning

Rashes, dermatitis, eczema, itching

Autonomic disturbance: excessive sweating, poor circulation, elevated heart rate

Autonomic disturbance: unusual sweating, poor circulation, elevated heart rate

Gastro-intestinal Disturbances</TD< tr>

 

Gastroenteritis, diarrhea; abdominal pain, constipation, “colitis”

Diarrhea, constipation, gaseousness, abdominal discomfort, colitis

Anorexia, weight loss, nausea, poor appetite

Anorexia; feeding problems/vomiting

Lesions of ileum & colon; increased gut permeability

Leaky gut syndrome

Inhibits dipeptidyl peptidase IV, which cleaves casomorphin

Inadequate endopeptidase enzymes needed for breakdown of casein & gluten

Abnormal Biochemistry

 

Binds -SH groups; blocks sulfate transporter in intestines, kidneys

Low sulfate levels

Has special affinity for purines & pyrimidines

Purine & pyrimidine metabolism errors lead to autistic features

Reduces availability of glutathione, needed in neurons, cells & liver to detoxify heavy metals

Low levels of glutathione; decreased ability of liver to detoxify heavy metals

Causes significant reduction in glutathione peroxidase and glutathione reductase

Abnormal glutathione peroxidase activities in erythrocytes

Disrupts mitochondrial activities, especially in brain

Mitochondrial dysfunction, especially in brain

Immune Dysfunction

 

Sensitivity due to allergic or autoimmune reactions; sensitive individuals more likely to have allergies, asthma, autoimmune-like symptoms, especially rheumatoid-like ones

More likely to have allergies and asthma; familial presence of autoimmune diseases, especially rheumatoid arthritis; IgA deficiencies

Can produce an immune response in CNS

On-going immune response in CNS

Causes brain/MBP autoantibodies

Brain/MBP autoantibodies present

Causes overproduction of Th2 subset; kills/inhibits lymphocytes, T-cells, and monocytes; decreases NK T-cell activity; induces or suppresses IFNg & IL-2

Skewed immune-cell subset in the Th2 direction; decreased responses to T-cell mitogens; reduced NK T-cell function; increased IFNg & IL-12

CNS Structural Pathology

 

Selectively targets brain areas unable to detoxify or reduce Hg-induced oxidative stress

Specific areas of brain pathology; many functions spared

Damage to Purkinje and granular cells

Damage to Purkinje and granular cells

Accummulates in amygdala and hippocampus

Pathology in amygdala and hippocampus

Causes abnormal neuronal cytoarchitecture; disrupts neuronal migration & cell division; reduces NCAMs

Neuronal disorganization; increased neuronal cell replication, increased glial cells; depressed expression of NCAMs

Progressive microcephaly

Progressive microcephaly and macrocephaly

Brain stem defects in some cases

Brain stem defects in some cases

Abnormalities in Neuro-chemistry

 

Prevents presynaptic serotonin release & inhibits serotonin transport; causes calcium disruptions

Decreased serotonin synthesis in children; abnormal calcium metabolism

Alters dopamine systems; peroxidine deficiency in rats resembles mercurialism in humans

Possibly high or low dopamine levels; positive response to peroxidine (lowers dopamine levels)

Elevates epinephrine & norepinephrine levels by blocking enzyme that degrades epinephrine

Elevated norepinephrine and epinephrine

Elevates glutamate

Elevated glutamate and aspartate

Leads to cortical acetylcholine deficiency; increases muscarinic receptor density in hippocampus & cerebellum

Cortical acetylcholine deficiency; reduced muscarinic receptor binding in hippocampus

Causes demyelinating neuropathy

Demyelination in brain

EEG Abnormalities / Epilepsy

 

Causes abnormal EEGs, epileptiform activity

Abnormal EEGs, epileptiform activity

Causes seizures, convulsions

Seizures; epilepsy

Causes subtle, low amplitude seizure activity

Subtle, low amplitude seizure activities

Population Characteristics

 

Effects more males than females

Male:female ratio estimated at 4:1

At low doses, only affects those geneticially susceptible

High heritability - concordance for MZ twins is 90%

First added to childhood vaccines in 1930s

First "discovered" among children born in 1930s

Exposure levels steadily increased since 1930s with rate of vaccination, number of vaccines

Prevalence of autism has steadily increased from 1 in 2000 (pre1970) to 1 in 500 (early 1990s), higher in 2000.

Exposure occurs at 0 - 15 months; clinical silent stage means symptom emergence delayed; symptoms emerge gradually, starting with movement & sensation

Symptoms emerge from 4 months to 2 years old; symptoms emerge gradually, starting with movement & sensation

 

 

Table II: Summary of Psychiatric Disturbances
Found in Autism & Mercury Poisoning

Mercury Poisoning

Autism

Extreme shyness, social withdrawal, feeling overly sensitive, introversion

Social deficits, social withdrawal, self reports of extreme shyness, aloofness

Mood swings; flat affect; mask face; laughing or crying without provocation; episodes of hysteria

Mood swings; flat affect in some; no facial expression; laughing or crying without reason

Anxiety; nervousness; tremulousness; somatization of anxious feelings

Anxiety, nervousness; anxiety disorder

Schizoid tendencies, neurosis, obsessive-compulsive traits, repetitive dreams

Schizophrenic traits; OCD traits; repetitive behaviors and thoughts

Lack of eye contact; being less talkative; hesitancy to engage others

Lack of eye contact, gaze avoidance; avoids conversation

Depression, lack of interest in life, lassitude, fatigue, apathy; feelings of hopelessness; melancholy

Association with depression; lack of initiative, diminished outward emotions

On the one hand, less overtly active, unwilling to go outside or be with others; on the other hand, increased restlessness

Tendency to withdraw, especially to own rooms, prefer to be alone; hyperactivity

Irrational fears

Irrational fears

Irritability, anger, and aggression; in children this may manifest as frequent and severe temper tantrums

Irritability and aggression; severe temper tantrums in children

Psychotic episodes; hallucinations, hearing voices; paranoid thoughts

Psychotic talk, paranoid thoughts

Impaired face recognition

Impaired face recognition

 

 

Table III: Summary of Speech, Language
& Hearing Deficits in Autism & Mercury Poisoning

Mercury Poisoning

Autism

Complete loss of speech in adults or children; failure to develop speech in infants

Delayed language onset; failure to develop speech

Dysarthria; speech difficulties from intention tremor; slow and slurred speech

Dysarthria; dyspraxia and oral-motor planning difficulties; unintelligible speech

Aphasia, the inability to use or understand words, inability to comprehend speech although ability to hear sound is intact

Speech comprehension deficits, although ability to hear sound is intact

Difficulties verbalizing; word retrieval problems

Echolalia; pronoun reversals, word meaning and pragmatic errors; limited speech production

Auditory disturbance; difficulties differentiating voices in a crowd

Difficulties following conversational speech with background noise

Sound sensitivity

Sound sensitivity

Hearing loss; deafness in very high doses

Mild to profound hearing loss

Poor performance on standardized language tests

Poor performance on verbal IQ tests

 

 

Table IV: Summary of Sensory Abnormalities
in Mercury Poisoning & Autism

Mercury Poisoning

Autism

Abnormal sensation or numbness around mouth and extremities (paresthesia); burning feet

Abnormal sensation in mouth and extremities; excessive mouthing of objects (infants); toe walking; difficulty grasping objects

Sound sensitivity

Sound sensitivity

Excessive pain when bumping; abnormal touch sensations; touch aversion

Insensitivity or overreaction to pain and touch; touch aversion; stiff to hold

Loss of position in space

Vestibular system abnormalities; difficulty orienting self in space

Normal pinprick tests

Normal pinprick tests

Table V: Summary of Motor Disorder Behaviors
in Mercury Poisoning & Autism

Mercury Poisoning

Autism

Involuntary jerking movements, e.g., arm flapping, ankle jerks, myoclonal jerks; choreiform movements; circling (cats); rocking; purposeless movement of extremities; twitching, shaking; muscular spasticity

Stereotyped movements such as arm flapping, jumping, circling, spinning, rocking; myoclonal jerks; choreiform movements

Unsteadiness in handwriting or an inability to hold a pen; deficits in eye-hand coordination; limb apraxia; intention tremors; loss of fine motor skills

Difficulty in writing with or holding a pen; poor eye-hand coordination; limb apraxia; problems carrying out intentional movements (praxia)

Ataxia: gait impairment; severity ranging from mild incoordination, clumsiness to complete inability to walk, stand, or sit; staggering, stumbling; loss of motor control

Abnormal gait and posture, clumsiness and incoordination; difficulties sitting, lying, crawling, and walking in infants and toddlers

Toe walking

Toe walking

Difficulty in chewing or swallowing

Difficulty chewing or swallowing

Unusual postures

Unusual postures

Areflexia

None described

Tremors in general, tremors of the face and tongue, hand tremors

None described

Table VI: Summary of Areas of Mental Impairment
in Mercury Poisoning & Autism

Mercury Poisoning

Autism

Some aspect of mental impairment in all symptomatic cases

Some aspect of mental impairment in all cases

Borderline intelligence on testing among previously normal individuals; mental retardation occurring in severe cases of pre-/postnatal exposure; some cases of MR reversible; primate studies indicate core intelligence spared with low exposures

Borderline intelligence or mental retardation on standard tests among previously normally appearing infants; some cases of MR "reversible"; indications that normal IQ might be present in MR-labeled individuals

Uneven performance on subtests of intelligence

Uneven performance on subtests of intelligence

Verbal IQ higher than performance IQ; compromised language/verbal expression and comprehension

Verbal IQ higher than performance IQ; compromised language/verbal expression and comprehension

Poor concentration, shortened attention span, general lack of attention; poor response inhibition

Lack of concentration, short attention span, lack of attention, difficulty shifting attention

Forgetfulness, loss of memory, particularly short term, verbal and auditory memory; mental confusion

Poor short term/working memory; poor auditory and verbal memory; lower verbal encoding abilities

Poor visual and perceptual motor skills, poor eye-hand coordination; impairment in simple reaction time

Poor visual and perceptual motor skills, poor eye-hand coordination; lowered performance on timed tests

Not reported as being tested

Difficulty processing multiple stimuli

Difficulty carrying out complex commands

Difficulty carrying out multiple commands

Alexia (inability to comprehend the meaning of written words)

Hyperlexia (ability to decode words while lacking word comprehension)

Deficits in constructional skills, conceptual abstraction, understanding abstract ideas and symbolism; degeneration of higher mental powers

Deficits in abstract/conceptual thinking, symbolism, understanding other's mental states; impairment in sequencing, planning, organizing

Lack of understanding of object permanence (primates)

Deficient understanding of object permanence (children)

Table VII: Summary of Unusual Behaviors
in Mercury-Poisoned Animals and Humans & in Autism

Mercury Poisoning

Autism

Stereotyped sniffing (rats)

Stereotyped, repetitive behaviors

Hyperactivity (rats); poor response inhibition (humans), restlessness

Hyperactivity; ADHD-traits

Agitation (humans)

Agitation

Insomnia; difficulty falling asleep (humans)

Insomnia; difficulty falling or staying asleep

Eating disorders: anorexia, poor appetite, food aversion, narrow food preferences, decided food preferences (salty food) (humans)

Eating disorders: anorexia; restricted diet/narrow food preferences; feeding and suckling problems

Masturbation, priapism (children)

Masturbatory tendencies

Unintelligible cries; continuous crying; unprovoked crying (infants and children)

Unprovoked crying

Self injurious behavior, including head banging and hitting the head (toddlers and children)

Self injurious behavior, including head banging and hitting the head

Grimacing (children)

Grimacing

Staring spells (infants and children)

Staring spells

Table VIII: Summary of Visual Impairments
Seen in Mercury Poisoning & Autism

Mercury Poisoning

Autism

Lack of eye contact; difficulties with visual fixation

Lack of eye contact; gaze abnormalities; problems in joint attention

"Visual impairments," blindness, near-sightedness, decreased visual acuity

"Visual impairments"; inaccurate or slow saccades; decreased functioning of the rods; retinal sheen

Light sensitivity, photophobia

Over-sensitivity to light

Blurred or hazy vision

Blurred vision

Constricted visual fields

Not described

Table IX: Physical Disturbances
in Mercury Poisoning & Autism

Mercury Poisoning

Autism

Increase in cerebral palsy; hyper- or hypotonia; paralysis, abnormal reflexes; spasticity; decreased muscle strength and motor power, especially in the upper body; incontinence; problems chewing, swallowing, and salivating

Increase in cerebral palsy; hyper- or hypotonia; decreased muscle strength, especially in the upper body; incontinence/toilet training difficulties; problems chewing and swallowing

Rashes, dermatitis, dry skin, itching; burning sensation

Rashes, dermatitis, eczema; itching

Autonomic disturbances: excessive sweating; poor circulation; elevated heart rate

Autonomic disturbances: sweating abnormalities; poor circulation; elevated heart rate

Table X: Summary of Gastrointestinal Problems
in Mercury Poisoning & Autism

Mercury Poisoning

Autism

Gastroenteritis, diarrhea; abdominal pain, rectal itching, constipation, "colitis"

Diarrhea, constipation, gaseousness, abdominal discomfort, colitis

Anorexia, weight loss, nausea, poor appetite

Anorexia; feeding difficulties, vomiting as infants

Lesions of the ileum and colon; increased intestinal permeability

Leaky gut syndrome from sulfur deficiency

Inhibits dipeptidyl peptidase IV, which cleaves casomorphin

Inadequate endopeptidase enzymes responsible for breakdown of casein and gluten

Table XI: Abnormalities in Biochemistry
Arising from Hg Exposure & Present in Autism

Mercury Poisoning

Autism

Ties up sulfur groups; prevents sulfate absorption

Low sulfate levels

Has special affinity for purines and pyrimidines

Errors in purine and pyrimidine metabolism can lead to autistic features

Depletes cellular tyrosine in yeast

PKU, arising from disruption in tyrosine production, results in autism

Reduces bioavailability of glutathione, necessary in cells and liver for heavy metal detoxification

Low levels of glutathione; decreased ability of liver to detoxify heavy metals

Can cause significant reduction in glutathione peroxidase and glutathione reductase

Abnormal glutathione peroxidase activities in erythrocytes

Disrupts mitochondrial activities, especially in brain

Mitochondrial dysfunction, especially in brain

Table XII: Summary of Immune System Abnormalities
in Mercury Exposure & Autism

Mercury Poisoning

Autism

Individual sensitivity due to allergic or autoimmune reactions; sensitive individuals more likely to have allergies and asthma, autoimmune-like symptoms, especially rheumatoid-like ones

More likely to have allergies and asthma; familial presence of autoimmune diseases, especially rheumatoid arthritis; IgA deficiencies

Can produce an immune response, even at low levels; can remain in CNS for years

Indications of on-going immune response in CNS

Presence of autoantibodies (IgG) to neuronal cytoskeletal proteins, neurofilaments, and myelin basic protein; astrogliosis; transient ANA and AnolA

Presence of autoantibodies (IgG and IgM) to cerebellar cells, myelin basis protein

Causes overproduction of Th2 subset; diminishes capacity to produce TNF(alpha) and IL-1; kills lymphocytes, T-cells, and monocytes; inhibits lymphocyte production; decreases NK T-cell activity; may induce or suppress IFN(gamma) and IL-2 production

Skewed immune-cell subset in the Th2 direction and abnormal CD4/CD8 ratios; decreased responses to T-cell mitogens; increased neopterin; reduced NK T-cell function; increased IFN(gamma) and IL-12

Table XIII: CNS Lesions
in Mercury Poisoning & Autism

Mercury Poisoning

Autism

Primarily impacts CNS

Neurological impairments primary

Selectively targets brain areas - those unable to detoxify heavy metals or reduce Hg-induced oxidative stress

Specific areas of brain pathology; many functions spared

Damage to Purkinje and granular cells

Damage to Purkinje and granular cells

Accummulates in amygdala and hippocampus

Pathology in amygdala and hippocampus

Causes abnormal neuronal cytoarchitecture; interferes with neuronal migration and depresses cell division in developing brains; reduces NCAMs

Neuronal disorganization; increased neuronal cell replication, small glia to neuron ration, increased glial cells; depressed expression of NCAMs

Head size differences: progressive microcephaly

Head size differences: progressive microcephaly and macrocephaly

Brain stem defects in some cases

Brain stem defects in some cases

Table XIV: Abnormalities in Neurons & Neurochemicals
from Mercury & in Autism

Mercury Poisoning

Autism

Can increase tissue concentration of serotonin in newborn rats; causes calcium disruptions in neurons, preventing presynaptic serotonin release and inhibiting serotonin transport activities

Serotonin abnormalities: decreased serotonin synthesis in children; over-synthesis in adults; elevated serotonin in platelets; positive response to SSRIs; calcium metabolism abnormalities present

Alters dopamine systems; disrupts calcium and increases synaptosome membrane permeability, which affect dopamine activities; peroxidine deficiency in rats results in acrodynia

Indications of either high or low dopamine levels; positive response to peroxidine by lowering dopamine levels; positive response to dopamine antagonists

Increases epinephrine and norepinephrine levels by blocking the enzyme which degrades epinephrine

Elevated norepinephrine and epinephrine; positive response to norepinephrine reuptake inhibitors

Elevates glutamate; decreases glutamate uptake; reduces functional activity of glutamatergic system

Elevated glutamate and aspartate

Alters choline acetyltransferase, leading to acetylcholine deficiency; inhibits acetylcholine neurotransmitter release via impact on calcium homeostasis; causes cortical acetylcholine deficiency; increases muscarinic receptor density in hippocampus and cerebellum

Abnormalities in cholinergic neurotransmitter system: cortical acetylcholine deficiency and reduced muscarinic receptor binding in hippocampus

Causes demyelating neuropathy

Demyelation in brain

Table XV: EEG Activity & Epilepsy
in Mercury Poisoning & Autism

Mercury Poisoning

Autism

Causes abnormal EEGs and unusual epileptiform activity

Abnormal EEG activity; epileptiform activity

Causes seizures, convulsions

Seizures; epilepsy

Causes subtle, low amplitude seizure activity

Subtle, low amplitude seizure activities