Human Diseases — Set 2

Correct Answer: A. Haemophilia

• **Haemophilia** = an X-linked recessive genetic disorder in which clotting factor VIII (Haemophilia A) or factor IX (Haemophilia B) is deficient or absent, preventing normal blood clotting; even minor injuries can cause prolonged, life-threatening bleeding. • **Inheritance pattern** — the gene is carried on the X chromosome; females with one defective X are carriers but usually unaffected; males with the defective X chromosome (XY) express the disease; the British royal family had a famous history of Haemophilia B passed through Queen Victoria. • Haemophilia is treated with regular infusions of the missing clotting factor concentrate; gene therapy approaches are currently showing promising results. • 💡 Option B (Sickle Cell Anaemia) is wrong because it is a haemoglobin disorder (HbS mutation) causing RBCs to deform into a sickle shape — it affects oxygen transport, not clotting; Option C (Night Blindness) is wrong because it is caused by Vitamin A deficiency, not genetics; Option D (Thalassemia) is wrong because it is a haemoglobin synthesis disorder affecting RBC count, not clotting.

Correct Answer: C. Sandfly

• **Sandfly** = Kala-azar (Visceral Leishmaniasis) is caused by the protozoan *Leishmania donovani* and is transmitted to humans through the bite of infected female *Phlebotomus* sandflies, which are tiny, hairy, blood-sucking insects active at dusk and dawn. • **Symptoms and name** — the disease causes fever, massive enlargement of the spleen and liver, severe anaemia, and darkening of the skin — hence the name "Kala-azar" (black fever in Hindi/Urdu); it attacks the immune system and is fatal if untreated. • India (Bihar, Jharkhand, UP, West Bengal) accounts for nearly 50% of global Kala-azar cases; the WHO targets its elimination as a public health problem. • 💡 Option A (Tsetse fly) is wrong because the Tsetse fly transmits African Sleeping Sickness (*Trypanosoma*), not Kala-azar; Option B (Fruit fly) is wrong because fruit flies (*Drosophila*) transmit no significant human diseases; Option D (Housefly) is wrong because houseflies mechanically transmit food-borne diseases but do not inject protozoan parasites.

Correct Answer: C. Iron

• **Iron** = iron deficiency is the most common nutritional deficiency worldwide and the leading cause of Anaemia; iron is a core component of haemoglobin (the oxygen-carrying protein in RBCs) — without sufficient iron, fewer and smaller red blood cells are produced, reducing oxygen delivery to tissues. • **Symptoms** — include fatigue, pallor, shortness of breath, dizziness, and brittle nails; iron-deficiency anaemia is especially prevalent in women of childbearing age and children; dietary sources include red meat, spinach, legumes, and fortified cereals. • Vitamin C significantly enhances iron absorption from plant sources (non-haem iron), while tea and coffee inhibit it. • 💡 Option A (Sodium) is wrong because sodium regulates fluid balance and nerve function — its deficiency causes hyponatraemia, not anaemia; Option B (Zinc) is wrong because zinc deficiency impairs immunity and wound healing, not haemoglobin synthesis; Option D (Potassium) is wrong because potassium deficiency causes muscle weakness and cardiac arrhythmia, not anaemia.

Correct Answer: D. Eyes

• **Eyes** = Glaucoma is a group of eye diseases characterised by damage to the optic nerve, typically caused by abnormally high intraocular pressure (IOP); the buildup of aqueous humour fluid inside the eye increases pressure, gradually destroying optic nerve fibres. • **Vision loss pattern** — Glaucoma first destroys peripheral (side) vision, progressing inward, often without pain or early symptoms — earning it the nickname "silent thief of sight"; if untreated, it leads to complete and irreversible blindness. • Glaucoma is the second leading cause of blindness worldwide after cataracts, affecting over 76 million people globally. • 💡 Option A (Skin) is wrong because skin diseases include dermatitis, psoriasis, and melanoma — none of which is Glaucoma; Option B (Bones) is wrong because bone diseases include osteoporosis and arthritis; Option C (Lungs) is wrong because lung diseases include TB, pneumonia, and asthma — all unrelated to Glaucoma.

Correct Answer: D. Brain

• **Brain** = Encephalitis is inflammation of the brain, most commonly caused by viral infections (Herpes simplex virus, Japanese Encephalitis virus, Nipah virus, etc.); in some cases, the immune system mistakenly attacks the brain (autoimmune encephalitis). • **Japanese Encephalitis (JE)** — the most common form in Asia, including India, is caused by the Japanese Encephalitis virus transmitted by *Culex* mosquitoes; it causes high fever, seizures, and altered consciousness, with a fatality rate up to 30% and neurological sequelae in survivors. • The term comes from Greek: *enkephalos* (brain) + *-itis* (inflammation); Meningitis is inflammation of the meninges (the membranes covering the brain), not the brain tissue itself. • 💡 Option A (Kidney) is wrong because kidney inflammation is called Nephritis; Option B (Heart) is wrong because heart muscle inflammation is called Myocarditis; Option C (Liver) is wrong because liver inflammation is called Hepatitis — all entirely different conditions from Encephalitis.

Correct Answer: A. Distant objects

• **Distant objects** = Myopia (short-sightedness/near-sightedness) occurs when the eyeball is too long or the cornea/lens is too curved, causing light to focus in front of the retina instead of on it; nearby objects appear sharp but distant objects are blurred. • **Correction** — Myopia is corrected using concave (diverging) lenses, which spread the incoming light rays so they converge correctly onto the retina; it is the most common refractive error globally, affecting approximately 2.6 billion people. • Hypermetropia (long-sightedness) is the opposite condition — distant objects are seen clearly but nearby objects are blurred; it is corrected with convex (converging) lenses. • 💡 Option B (Colours) is wrong because difficulty seeing colours is called Colour Blindness (dyschromatopsia), a different condition caused by cone cell defects; Option C (Small text) is wrong because difficulty reading small print at close range is Presbyopia (age-related lens stiffening), not Myopia; Option D (In the dark) is wrong because difficulty seeing in dim light is Night Blindness (Nyctalopia), caused by Vitamin A deficiency.

Correct Answer: B. Rabies

• **Rabies** = caused by the Rabies lyssavirus, transmitted through the saliva of an infected animal (most commonly dog bites); the virus travels up peripheral nerves to the brain, causing fatal encephalitis; the name "Hydrophobia" refers to the characteristic spasm of throat muscles when attempting to swallow water. • **Post-exposure prophylaxis (PEP)** — once symptoms appear, rabies is nearly 100% fatal; however, prompt wound cleaning and PEP vaccination after a bite can prevent the disease from developing; the Rabies vaccine was developed by Louis Pasteur in 1885. • India accounts for approximately 36% of global rabies deaths, with street dogs being the primary transmission source. • 💡 Option A (Plague) is wrong because Plague is caused by *Yersinia pestis* bacterium and is characterised by buboes and septicaemia, not hydrophobia; Option C (Tetanus) is wrong because Tetanus is caused by *Clostridium tetani* toxin and causes jaw spasm (lockjaw) and muscle rigidity; Option D (Cholera) is wrong because Cholera is a bacterial disease causing profuse diarrhoea — the patient craves water, not fears it.

Correct Answer: C. HIV/AIDS

• **HIV/AIDS** = ELISA (Enzyme-Linked Immunosorbent Assay) is the standard first-line screening test for HIV infection; it detects HIV antibodies (and p24 antigen in 4th-generation tests) in a blood sample with very high sensitivity — making it ideal for mass screening. • **Confirmatory test** — a positive ELISA result must be confirmed with the Western Blot test or an HIV-1/HIV-2 antibody differentiation assay, since false positives can occur; ELISA was first developed in the early 1970s and has broad applications across many infectious diseases beyond HIV. • The "window period" — the time between HIV infection and the appearance of detectable antibodies — is typically 3–12 weeks with modern 4th-generation ELISA tests. • 💡 Option A (Cancer) is wrong because cancer screening uses tumour markers (PSA for prostate, CA-125 for ovarian cancer), biopsy, and imaging — not ELISA as primary screening; Option B (Tuberculosis) is wrong because TB is diagnosed via sputum culture, AFB staining, or the Mantoux test; Option D (Diabetes) is wrong because diabetes is diagnosed by fasting blood glucose, HbA1c, or OGTT tests, not ELISA.

Correct Answer: D. Beri-beri

• **Beri-beri** = caused by Thiamine (Vitamin B1) deficiency; Thiamine is essential for carbohydrate metabolism and nerve function; its absence causes damage to the nervous system (dry beri-beri) and/or the cardiovascular system with fluid accumulation (wet beri-beri). • **Two forms** — Dry beri-beri presents with peripheral neuropathy (numbness, weakness in limbs); Wet beri-beri additionally causes heart failure and oedema (fluid accumulation); Wernicke-Korsakoff syndrome, seen in chronic alcoholics, is a severe neurological form of Thiamine deficiency. • Beri-beri was historically common in regions where polished (white) rice was the staple food, as the milling process removes the Thiamine-rich bran layer. • 💡 Option A (Pellagra) is wrong because Pellagra is caused by Niacin (B3) deficiency, not Thiamine; Option B (Cheilosis) is wrong because cracking of lip corners is caused by Riboflavin (B2) deficiency; Option C (Scurvy) is wrong because Scurvy is caused by Vitamin C deficiency.

Correct Answer: D. Fungus

• **Fungus** = Athletes' Foot (Tinea pedis) is caused by dermatophyte fungi, most commonly *Trichophyton rubrum*; these fungi feed on keratin in the skin, causing itching, scaling, redness, and blisters between the toes and on the soles of the feet. • **Transmission and risk** — the fungus thrives in warm, moist environments such as locker rooms, swimming pools, and communal showers; people who wear tight, non-breathable shoes or keep their feet damp are most susceptible; treated with antifungal creams containing clotrimazole or terbinafine. • Athletes' Foot belongs to the dermatophytosis group (ringworm family); similar fungal infections include Tinea corporis (body ringworm), Tinea capitis (scalp ringworm), and Tinea cruris (jock itch). • 💡 Option A (Bacteria) is wrong because bacterial skin infections include impetigo and cellulitis — not Athletes' Foot; Option B (Protozoa) is wrong because protozoal skin involvement is rare (e.g., cutaneous leishmaniasis) and does not cause Athletes' Foot; Option C (Virus) is wrong because viral skin infections include chickenpox, warts, and cold sores — none presenting as Athletes' Foot.