Heavy Metal Poisoning and Pica Behavior

Heavy Metal Poisoning

• Heavy metals like lead (Pb), mercury (Hg), iron (Fe), and arsenic (As) are toxic.
• Lead is used in automotive batteries, semiconductors, pesticides, and pigments (As2S3 and As4S4).
• Mercury is used in dentistry, as an antiseptic, in batteries, explosives, and pesticides.
• Arsenic is discovered by Albertus Magnus. It is used in pesticides, wood preservatives and pigments.

Arsenic

• Arsenic is known as "the silent killer" and "the King of Poisons".
• It was used in the "Poison of Kings".
• Inorganic arsenic (As2O3, As2O5) is the major form in humans.
• Organic arsenic is less toxic, found in soil, pesticides, and marine organisms.

Pica Behavior

• Pica is a psychological disorder characterized by compulsive appetite for non-nutritive substances.
• Substances include ice (pagophagia), hair (trichophagia), paper (xylophagia), drywall or paint and chalk, metal (metallophagia), stones (lithophagia), soil (geophagia), glass (hyalophagia), and feces (coprophagia).

Soil Pica Behavior

• Children ingest large amounts of soil, especially clay, which can be part of cultural practices.
• Children aged 1-2 years have a higher incidence of soil pica.

Pathophysiology of Arsenic

• Trivalent forms of arsenic bind to sulfhydryl groups to suppress enzymes.
• This can result in acidosis, inhibition of Krebs cycle and oxidative phosphorylation of ATP production.
• Pentavalent arsenic can replace phosphate ester bonds in ATP to form a non-high energy bond.
• This lessens enzymatic effect.
• Lead to endothelial damage, capillary leakage, and shock.

Clinical Picture of Acute Arsenic Toxicity

• Gastrointestinal signs include garlic or metallic taste, burning mucosa, vomiting like cholera, severe diarrhea.
• Abdominal pain, hematemesis, and hematochezia (rectal bleeding).
• Skin (Erythema, hyperpigmentation & hyperkeratosis in chronic exposure, black foot disease)
• Liver (Hepatitis, necrosis, fibrosis)
• CNS (Delirium, convulsions, coma)
• Pulmonary (pulmonary edema and failure)
• Circulatory issues (Tachycardia, dehydration, and hypovolemic shock).
• Kidney (proteinuria, hematuria, oliguria, acute renal failure).
• Hematologic (Bone marrow depression → anemia, thrombocytopenia or aplastic anemia, hemolytic anemia or hemoglobinuria with arsenic gas inhalation.)

Treatment of Arsenic Poisoning

• Emesis, gastric lavage, activated charcoal and whole bowel irrigation are not effective for inorganic arsenic poisoning.
• Supportive care may be necessary.
• Chelation therapy might be promptly used with succimer (DMSA) being the best, followed then by BAL (British anti-Lewisite) - IM , and D-penicillamine as less effective.

Lead Poisoning

• Lead is commonly used in certain industries and products.
• Lead forms include inorganic ones such as: lead arsenate in insecticides, lead azide in primers, lead carbonate in paints, and lead chromate in pastel paints.
• Organic forms of lead include tetraethyl lead in gasoline additives used until 1978.
• Lead exposure comes from paints, water (lead pipes, solder, or glazed crystal), air (car batteries and radiator recycling), and food (cans).

Pathophysiology of Lead

• Lead affects the nervous system (CNS) and the peripheral nervous system as well as the hematologic and renal systems.
• Neurotoxins can disrupt Ach, dopamine, and other neurotransmitter functions.
• It may also impact the kidneys (lead nephropathy), resulting in decreased urine production.
• Hematologic effects include anemia in children.
• It may lead to reproduction issues in both genders.

Clinical Picture of Lead Toxicity

• Gastrointestinal effects include metallic taste, burning, nausea, vomiting, severe abdominal pain, hemorrhage and dehydration.
• Central nervous system (CNS) effects include lead encephalopathy, behavioral changes, fatigue or lethargy, seizures and coma in acute exposure cases.
• Other effects include non-specific vague body aches, constipation, blue line on gums, lead colic, peripheral neuritis with potential causes of wrist or foot drop, and optic neuritis.

Treatment of Lead Toxicity

• Reducing lead exposure is the primary step for adults.
• Children with lead levels of 15-19 are treated by careful environmental history and pre-exposure risk reduction.
• For level over 20, chelation therapy may or may not be routinely used.
• Symptomatic treatment includes anemia treatment and hemodialysis for renal failure issues.
• Chelating agents could be used including dimercaprol (BAL), calcium disodium EDTA, and D-penicillamine; however, dimercaprol (BAL) is preferred for encephalopathic cases.

Mercury Toxicity

• Mercury can be elemental, inorganic (e.g., mercuric chloride, used in antiseptics and disinfectants) or organic (e.g., methyl mercury, found in seafood, grain and seed fumigants and fungicides.
• Inorganic mercury is also used in products like batteries and explosives.
• Elemental mercury can affect lungs (chemical pneumonitis).
• Inorganic mercury can affect the gastrointestinal tract (GIT) and kidneys (hemorrhagic gastroenteritis and ATN).
• Organic mercury affects predominantly the CNS and affects especially the fetus .
• Mercury is not absorbed on ingestion in its elemental form.

Pathophysiology of Mercury

• Inorganic and elemental mercury directly affects the targeted organs and tissues.
• Organic mercury is readily absorbed.
• Mercury inhibits selenoenzymes and depletes cellular selenium, and causes irreversible oxidative damage which can be fatal.

Clinical Picture of Acute Mercury Toxicity (Elemental)

• Pulmonary effects (cough, chills, fever, dyspnea, chemical pneumonitis, pulmonary edema).
• Gastrointestinal problems include metallic taste, nausea, vomiting, diarrhea and dysphagia.
• Central nervous system (CNS) effects include headaches, weakness, and visual disturbances.

Clinical Picture of Acute Mercury Toxicity (Inorganic)

• Symptoms of inorganic ingestion may include metallic taste, oral pain, burning sensations, nausea or vomiting, diarrhea, abdominal pain, hemorrhagic gastroenteritis, and dehydration which can cause orthostatic hypotension.
• Renal effects include acute tubular necrosis) ATN).

Clinical Picture of Chronic Mercury Toxicity (Mercurialism)

• Pulmonary effects include obstructive and restrictive lung diseases such as pulmonary fibrosis.
• Renal problems such as Fanconi's syndrome.
• Gastrointestinal toxicity is minimal.

Investigations of Mercury Toxicity

• Blood tests (CBC, renal function tests; blood mercury levels).

Treatment of Mercury Toxicity

• Stop further exposure.
• Chelation therapy may use penicillamine, or DMSA, and other agents.
• Renal problems are treated with hemodialysis.

Iron Toxicity

• Iron is widely available in iron-fortified foods, and other supplements.
• Iron toxicity can occur via accidental poisoning or ingestion of excess food supplements.

Pathophysiology of Iron Toxicity

• Iron exposure causes local corrosive action on GI mucosa, leading to oxidative damage
• Absorption of iron, bound to transferrin, is eventually saturated.
• Excess iron causes oxidative damage in organ systems and is a mitochondrial toxin leading to disturbances of energy metabolism and oxidative phosphorylation reactions

Clinical Picture of Acute Iron Toxicity

• Early symptoms associated with ingestion occur 1-6 hours after ingestion
• GI-effects include severe irritation, nausea, vomiting, abdominal pain, severe diarrhea and bloody stools; shock.
• In severe cases, CNS depression may cause lethargy and coma.
• Stage II (Quiescent phase) shows temporary improvement or false improvement, lasting up to 24 hours post ingestion.
• Stage III lasts 12-48 hours with metabolic acidosis and related symptoms, such as fever and leucocytosis.
• Stage IV (days 2-3 after ingestion) leads to hepatic necrosis, liver failure (jaundice, hypoglycemia and coagulation issues).
• Stage V (weeks 2-8 post ingestion) results in intestinal scarring with or without obstruction.

Investigations of Iron Toxicity

• Serum iron levels in the blood for diagnosis (normal range is between 80-180 ug/dL).
• A high level usually correlates with gastrointestinal toxicity between 300-500 ug/dL.
• Markedly higher levels between 500-1000 indicates more systemic effects.
• Levels exceeding 1000 ug/dL may significantly increase morbidity and mortality rates.
• Renal function tests (BUN, creatinine) and coagulation profiles are used to detect other complications.
• X-ray abdomen may be used in case of swallowed radiopaque tablets.

Treatment of Iron Toxicity

• Emergency measures (ABCs) may be needed with methods like gastric lavage and whole bowel irrigation.
• Follow up with X-rays to evaluate the treatment efficacy.
• Activated charcoal is ineffective with iron poisoning.
• Deferoxamine, a chelating agent is used for severe cases.
• Symptomatic treatment involves using fluids and liver support remedies.
• Acidosis corrections are often necessary.

Chronic Iron Toxicity

• Chronic blood transfusions in patients with hemolytic anemia.
• Iron accumulation in various tissues, leading to hemochromatosis.
• Deposition of iron in the pancreas may cause diabetes.

Clinical Picture of Chronic Iron Toxicity

• Joint pain, primarily in fingers; skin bronzing or tanning.
• Erectile dysfunction and irregular menstrual cycles.
• Increased urination (polyuria).
• Thirst (polydipsia).
• Hair loss.
• Cardiomyopathy (weakening of the heart).

This quiz explores the dangers of heavy metal poisoning from substances like lead, mercury, and arsenic. It also delves into the psychological disorder known as pica, which involves an appetite for non-nutritive substances. Test your knowledge on the toxicity of these elements and their effects on human health.