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