Human Diseases — Set 3

Correct Answer: A. Cadmium

• **Cadmium** = Itai-itai disease ("ouch-ouch" in Japanese) was caused by cadmium-contaminated irrigation water from the Jinzu River in Toyama Prefecture, Japan, in the 1950s–60s; the Mitsui Mining Company had discharged cadmium-laden wastewater upstream. • **Pathology** — cadmium accumulates in the kidneys, damaging the renal tubules and causing calcium to be excreted in urine (hypercalciuria); this leads to severe osteoporosis and osteomalacia, causing extremely brittle bones that fracture easily — even from coughing — hence the agonised cries "itai-itai". • Itai-itai disease is one of Japan's "Big Four" pollution diseases; cadmium enters the food chain primarily through contaminated rice and vegetables grown in polluted soil. • 💡 Option B (Mercury) is wrong because mercury poisoning causes Minamata disease (neurological damage), not bone disease; Option C (Arsenic) is wrong because arsenic causes arsenicosis — skin lesions, cancers, and peripheral vascular disease; Option D (Lead) is wrong because lead poisoning (plumbism) causes cognitive impairment and anaemia, not brittle bones.

Correct Answer: B. Niacin (B3)

• **Niacin (B3)** = Pellagra is caused by deficiency of Niacin (nicotinic acid) or its precursor tryptophan; Niacin is essential for NAD and NADP synthesis, which are crucial coenzymes in cellular energy metabolism and DNA repair. • **The 4Ds of Pellagra** — the disease presents with four classic signs: Dermatitis (sun-sensitive skin rash on sun-exposed areas), Diarrhoea, Dementia (cognitive decline), and Death if untreated; it was historically common in populations where maize (corn) was the primary staple food. • Maize contains niacin in a bound form (niacytin) that the human body cannot absorb unless the corn is treated with lime water (nixtamalization) — a traditional practice of Mesoamerican cultures that prevented pellagra. • 💡 Option A (Cyanocobalamin/B12) is wrong because B12 deficiency causes megaloblastic anaemia and subacute combined degeneration of the spinal cord; Option C (Riboflavin/B2) is wrong because B2 deficiency causes cheilosis, angular stomatitis, and glossitis; Option D (Pyridoxine/B6) is wrong because B6 deficiency causes peripheral neuropathy and seborrhoeic dermatitis.

Correct Answer: B. Sleeping Sickness

• **Sleeping Sickness** (African Trypanosomiasis) = caused by the protozoan *Trypanosoma brucei*, transmitted through the bite of infected Tsetse flies (*Glossina* species) found exclusively in sub-Saharan Africa; the parasite invades the central nervous system. • **Disease progression** — Stage 1 involves fever, swollen lymph nodes (Winterbottom's sign), headaches, and joint pain; Stage 2 (neurological stage) occurs when the parasite crosses the blood-brain barrier, causing sleep cycle disruption, confusion, and the characteristic excessive daytime sleepiness — hence "sleeping sickness" — followed by coma and death. • The related disease *Trypanosoma cruzi* (Chagas disease) is transmitted by Triatomine "kissing bugs" in Latin America — this is a completely different disease and vector. • 💡 Option A (Malaria) is wrong because malaria is caused by *Plasmodium* transmitted by *Anopheles* mosquitoes, not Tsetse flies; Option C (Dengue) is wrong because dengue is a viral disease spread by *Aedes aegypti* mosquitoes; Option D (Kala-azar) is wrong because Kala-azar is caused by *Leishmania donovani* and spread by Sandflies, not Tsetse flies.

Correct Answer: D. Bones

• **Bones** = Osteoporosis is a metabolic bone disease characterised by decreased bone mineral density (BMD) and deterioration of bone microarchitecture, making bones porous, brittle, and highly susceptible to fracture — especially of the hip, spine, and wrist. • **Risk factors and mechanism** — bone mass peaks around age 30 and naturally declines with age; in women, the sharp drop in oestrogen after menopause accelerates bone loss; calcium and Vitamin D deficiency, sedentary lifestyle, and smoking also contribute; diagnosed by DEXA scan. • Osteoporosis is sometimes called the "silent disease" because bone loss occurs without symptoms until a fracture occurs; hip fractures in the elderly carry up to 30% mortality within one year. • 💡 Option A (Teeth) is wrong because tooth decay is dental caries (caused by bacteria) and weakening of jaw bone is a separate process — not Osteoporosis; Option B (Nerves) is wrong because nerve degeneration is involved in conditions like Multiple Sclerosis and Peripheral Neuropathy; Option C (Muscles) is wrong because muscle wasting is called Sarcopenia or Muscular Dystrophy, not Osteoporosis.

Correct Answer: A. Vitamin A

• **Vitamin A** = Xerophthalmia (from Greek: *xeros* = dry, *ophthalmos* = eye) is caused by Vitamin A deficiency; Vitamin A (retinol) is essential for the production of rhodopsin (visual purple) in the rod cells of the retina — its deficiency first causes Night Blindness, then progresses to Xerophthalmia (dry, rough cornea) and Keratomalacia (corneal ulceration leading to total blindness). • **Progression** — early: Night Blindness → Bitot's spots (foamy white deposits on the conjunctiva) → Xerophthalmia → Keratomalacia (irreversible corneal destruction); Vitamin A deficiency is the leading cause of preventable blindness in children worldwide. • India administers Vitamin A supplementation to children under 5 years under the National Nutritional Anaemia Prophylaxis Programme to combat this. • 💡 Option B (Vitamin E) is wrong because Vitamin E deficiency causes nerve damage (peripheral neuropathy) and haemolytic anaemia, not dry eyes; Option C (Vitamin C) is wrong because its deficiency causes Scurvy (bleeding gums, skin haemorrhage), not eye disease; Option D (Vitamin B) is wrong because B vitamins collectively are involved in energy metabolism — their specific deficiencies cause conditions like Beri-beri, Pellagra, and anaemia.

Correct Answer: A. Hypertension

• **Hypertension** = also called high blood pressure, is a non-communicable disease (NCD) because it is not caused by a pathogen and cannot be transmitted from person to person; it results from lifestyle factors (obesity, high salt intake, stress, physical inactivity, smoking) and genetic predisposition. • **NCD classification** — Non-communicable diseases are also called chronic diseases or lifestyle diseases; the WHO's four major NCD categories are cardiovascular diseases, cancers, chronic respiratory diseases, and diabetes; Hypertension is a primary risk factor for all cardiovascular diseases. • Hypertension is called the "silent killer" because it has no symptoms until it causes a heart attack, stroke, kidney failure, or retinal damage — it is estimated to affect 1.28 billion adults worldwide. • 💡 Option B (Cholera) is wrong because it is a communicable bacterial disease caused by *Vibrio cholerae* and spreads via contaminated water; Option C (Influenza) is wrong because it is a communicable viral respiratory disease that spreads through droplets; Option D (Smallpox) is wrong because it was a highly contagious viral disease (eradicated in 1980) — the opposite of a non-communicable disease.

Correct Answer: D. Vibrio cholerae

• **Vibrio cholerae** = a comma-shaped, gram-negative bacterium that produces cholera toxin (CT), which acts on the intestinal epithelium to cause massive secretion of chloride and water into the gut lumen — producing the characteristic profuse "rice-water" diarrhoea that can cause severe dehydration and death within hours. • **Transmission** — spreads via the faecal-oral route through contaminated drinking water or food; Oral Rehydration Solution (ORS) is the cornerstone of treatment; cholera thrives in areas with poor sanitation and has caused seven global pandemics, the current one (7th) being caused by the El Tor biotype. • John Snow's famous epidemiological investigation of the 1854 Broad Street cholera outbreak in London established the foundation of modern epidemiology. • 💡 Option A (Bacillus anthracis) is wrong because it causes Anthrax — a disease of cattle and humans, not cholera; Option B (Salmonella typhi) is wrong because it causes Typhoid fever, not cholera; Option C (Clostridium tetani) is wrong because it causes Tetanus by producing a neurotoxin that causes muscle spasms — completely unrelated to diarrhoeal disease.

Correct Answer: D. Diphtheria

• **Diphtheria** = the Schick Test determines whether a person is susceptible or immune to Diphtheria; a small amount of diphtheria toxin is injected intradermally — if the person lacks protective antibodies, the skin shows redness and swelling (positive result = susceptible); if immune, no reaction occurs. • **Diphtheria itself** — caused by *Corynebacterium diphtheriae*, it produces a powerful exotoxin that forms a characteristic grey-white pseudomembrane in the throat and upper airways, which can obstruct breathing ("bull neck" swelling); the toxin also damages the heart and nerves. • The Schick Test was developed by Hungarian-American paediatrician Béla Schick in 1913; it has largely been replaced by vaccination status assessment and serology. • 💡 Option A (Measles) is wrong because measles susceptibility is tested by checking vaccination records or measles IgG antibody titres, not the Schick test; Option B (Pertussis) is wrong because whooping cough is diagnosed by nasopharyngeal culture or PCR for *Bordetella pertussis*; Option C (Mumps) is wrong because mumps (parotid gland inflammation) is caused by the Paramyxovirus and diagnosed serologically.

Correct Answer: B. Dengue

• **Dengue** = caused by the Dengue virus (DENV), a flavivirus with four serotypes (DENV-1 to DENV-4), transmitted to humans through the bite of an infected *Aedes aegypti* mosquito (and to a lesser extent *Aedes albopictus*); it is the fastest-spreading mosquito-borne viral disease in the world. • **Clinical features** — Dengue fever presents with sudden high fever, severe headache, pain behind the eyes (retro-orbital pain), joint and muscle pain ("breakbone fever"), and a characteristic skin rash; Dengue Haemorrhagic Fever (DHF) is a severe, potentially fatal form with plasma leakage and bleeding. • *Aedes aegypti* mosquitoes breed in clean, stagnant water in urban areas (flower pots, tyres, water tanks) and bite predominantly during the day — unlike *Anopheles* mosquitoes which bite at night. • 💡 Option A (Malaria) is wrong because malaria is caused by the protozoan *Plasmodium* spread by *Anopheles* mosquitoes, not *Aedes*; Option C (Kala-azar) is wrong because it is caused by *Leishmania donovani* and spread by Sandflies, not mosquitoes; Option D (Filaria) is wrong because it is caused by the nematode *Wuchereria bancrofti* and spread by *Culex* mosquitoes.

Correct Answer: D. Poor blood clotting

• **Poor blood clotting** = Vitamin K (phylloquinone) is essential for the synthesis of clotting factors II (prothrombin), VII, IX, and X in the liver; without Vitamin K, these factors cannot be activated, leading to prolonged bleeding from wounds, spontaneous bruising, and haemorrhage. • **Sources and antagonism** — Vitamin K is found in green leafy vegetables (spinach, broccoli, kale) and is also produced by gut bacteria (Vitamin K2); warfarin (a common anticoagulant drug) works precisely by blocking Vitamin K activity — making it an antagonist used to prevent blood clots in patients with heart disease. • Newborn babies are routinely given Vitamin K injections at birth because they are born with very low levels, making them susceptible to Haemorrhagic Disease of the Newborn (HDN). • 💡 Option A (Nerve damage) is wrong because nerve damage is associated with Vitamin B12 and Vitamin E deficiencies, not Vitamin K; Option B (Night Blindness) is wrong because Night Blindness is caused by Vitamin A deficiency — affecting rhodopsin production in retinal rods; Option C (Scurvy) is wrong because Scurvy is caused by Vitamin C deficiency affecting collagen synthesis.