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 others 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
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