Human Diseases — Set 5

Correct Answer: C. Bacteria

• **Bacteria** = Tetanus is caused by Clostridium tetani, an anaerobic, spore-forming bacterium that releases tetanospasmin — one of the most potent biological toxins known — when it infects deep, oxygen-poor wounds. • **Toxin mechanism** — tetanospasmin travels up motor neurons to the spinal cord where it blocks inhibitory neurotransmitters (glycine and GABA), causing uncontrolled muscle spasms and the characteristic "lockjaw" (trismus). • C. tetani spores are ubiquitous in soil and can survive boiling; the TT (Tetanus Toxoid) vaccine provides effective protection. • 💡 Option A (Virus) is wrong because viruses do not produce tetanospasmin; tetanus cannot be caused by any viral agent; Option B (Fungus) is wrong because pathogenic fungi cause diseases like ringworm and candidiasis, not tetanus; Option D (Amoeba) is wrong because amoeba causes diseases like amoebiasis and amoebic dysentery, not tetanus.

Correct Answer: B. Kidney inflammation

• **Kidney inflammation** = Bright's Disease is a historical umbrella term for nephritis — inflammation of the kidney glomeruli or tubules — characterised by protein and blood in urine, oedema, and hypertension. • **Named after Richard Bright** — the 19th-century British physician who first described the condition in 1827 by correlating clinical signs with post-mortem kidney findings. • Today the condition is clinically divided into glomerulonephritis, nephrotic syndrome, and other renal inflammatory disorders. • 💡 Option A (Lung infection) is wrong because lung infections cause pneumonia or bronchitis, not nephritis; Option C (Liver scarring) is wrong because liver scarring is specifically called cirrhosis; Option D (Heart blockage) is wrong because cardiac blockages are associated with ischaemic heart disease and atherosclerosis.

Correct Answer: D. Vitamin A

• **Vitamin A** = Retinol is the principal pre-formed Vitamin A found in animal products; it is a fat-soluble vitamin essential for vision (especially in dim light), immune function, skin integrity, and foetal development. • **Role in vision** — Retinol is converted to retinal (retinaldehyde), which combines with the protein opsin in rod cells to form rhodopsin, the pigment responsible for night vision. • Beta-carotene (found in carrots and leafy greens) is a provitamin A carotenoid that the body converts into retinol as needed. • 💡 Option A (Vitamin K) is wrong because Vitamin K's chemical forms are phylloquinone and menaquinone, not retinol; Option B (Vitamin D) is wrong because Vitamin D's active form is calcitriol (cholecalciferol), not retinol; Option C (Vitamin E) is wrong because Vitamin E refers to tocopherols, which are antioxidant compounds distinct from retinol.

Correct Answer: D. Joints and Muscles

• **Joints and Muscles** = Rheumatism is a broad clinical term covering disorders that cause pain, stiffness, swelling, and reduced range of motion in joints and the surrounding soft tissues including muscles, tendons, and ligaments. • **Rheumatoid Arthritis** — the most recognised autoimmune form in which the immune system attacks the synovial lining of joints, causing chronic inflammation and eventual joint destruction. • Rheumatic diseases collectively affect over 200 million people globally and are the leading cause of disability in many countries. • 💡 Option A (Eyes) is wrong because eye inflammation is called uveitis or conjunctivitis; Option B (Lungs) is wrong because lung disorders include pneumonia, asthma, and tuberculosis; Option C (Intestines) is wrong because intestinal inflammation is called colitis or Crohn's disease.

Correct Answer: D. Influenza

• **Influenza** = the influenza virus spreads person-to-person primarily through respiratory droplets (>5 µm) expelled when an infected person coughs, sneezes, or talks, and can also spread via smaller aerosols and contaminated surfaces. • **Seasonal variation** — influenza viruses undergo antigenic drift (small mutations) each season and antigenic shift (major reassortment) occasionally, which is why annual flu vaccines are reformulated. • Influenza causes 3–5 million severe cases and 290,000–650,000 respiratory deaths globally each year according to the WHO. • 💡 Option A (Malaria) is wrong because malaria spreads through the bite of an infected female Anopheles mosquito, not through air; Option B (Cholera) is wrong because cholera is a waterborne disease caused by Vibrio cholerae in contaminated water; Option C (Typhoid) is wrong because typhoid fever is transmitted through faecally contaminated food and water, not respiratory droplets.

Correct Answer: B. Whooping cough

• **Whooping cough** = Pertussis is caused by Bordetella pertussis, a bacterium that attaches to the cilia lining the respiratory tract and releases toxins causing prolonged, violent coughing fits followed by a characteristic high-pitched "whoop" sound during the forced inhalation. • **Three phases** — the disease progresses through catarrhal (cold-like), paroxysmal (severe coughing), and convalescent stages over 6–10 weeks; infants under 1 year are at greatest risk of fatal complications. • Pertussis is the "P" component of the DPT vaccine; despite vaccination, it remains one of the most prevalent vaccine-preventable diseases globally. • 💡 Option A (Mumps) is wrong because mumps is a viral disease (Paramyxovirus) causing swelling of the parotid salivary glands, not coughing; Option C (Measles) is wrong because measles is a paramyxoviral disease characterised by rash and Koplik's spots; Option D (Smallpox) is wrong because smallpox is caused by the Variola virus and is eradicated since 1980.

Correct Answer: A. Sleeping Sickness

• **Sleeping Sickness** = African Trypanosomiasis (Sleeping Sickness) is caused by Trypanosoma brucei, a protozoan transmitted through the bite of infected tsetse flies (Glossina species) found in sub-Saharan Africa. • **Two stages** — the haemolymphatic stage involves fever and headaches, while the neurological stage (when the parasite crosses the blood-brain barrier) causes sleep disruption, confusion, and coma — hence the name "sleeping sickness". • Without treatment, sleeping sickness is almost invariably fatal; the disease has been substantially reduced through vector control and active screening programmes. • 💡 Option B (Kala-azar) is wrong because kala-azar (visceral leishmaniasis) is caused by Leishmania donovani and spread by the sandfly, not tsetse fly; Option C (Filaria) is wrong because filariasis is caused by a nematode worm Wuchereria bancrofti transmitted by female Culex mosquitoes; Option D (Malaria) is wrong because malaria is caused by Plasmodium protozoa spread by female Anopheles mosquitoes.

Correct Answer: D. Pernicious Anaemia

• **Pernicious Anaemia** = caused specifically by the inability to absorb Vitamin B12 due to a lack of intrinsic factor (a glycoprotein secreted by gastric parietal cells); without B12, red blood cell precursors cannot divide properly, producing fewer but abnormally large (megaloblastic) cells. • **Intrinsic factor deficiency** — most commonly results from an autoimmune attack on parietal cells or intrinsic factor itself, making this a form of autoimmune gastritis rather than simple dietary deficiency. • B12 is also essential for myelin synthesis; its deficiency causes subacute combined degeneration of the spinal cord alongside the anaemia. • 💡 Option A (Aplastic Anaemia) is wrong because aplastic anaemia results from bone marrow failure causing a reduction in all blood cell types, not B12 deficiency; Option B (Sickle Cell Anaemia) is wrong because it is a genetic haemoglobin disorder (HbS mutation), completely unrelated to B12; Option C (Iron-deficiency Anaemia) is wrong because it results from insufficient iron causing small (microcytic), pale (hypochromic) red cells, the opposite of megaloblastic cells.

Correct Answer: C. Swelling of salivary glands

• **Swelling of salivary glands** = Mumps (Paramyxovirus) specifically infects and inflames the parotid salivary glands — the largest salivary glands located just below and in front of the ears — causing the characteristic puffy-cheek appearance. • **Complications** — in post-pubertal males, mumps can cause orchitis (testicular inflammation) that may rarely lead to infertility; other complications include viral meningitis and pancreatitis. • Mumps is the "M" component of the MMR (Measles-Mumps-Rubella) triple vaccine given in the childhood immunisation schedule. • 💡 Option A (Skin rashes) is wrong because skin rashes are characteristic of measles and rubella, not mumps; Option B (Weak bones) is wrong because bone weakness relates to calcium/Vitamin D deficiency diseases like rickets; Option D (Bleeding gums) is wrong because bleeding gums are a symptom of scurvy (Vitamin C deficiency) or periodontal disease.

Correct Answer: A. Skin

• **Skin** = Eczema (atopic dermatitis) is a chronic inflammatory skin condition characterised by dry, itchy, red, and cracked patches that periodically flare up; it results from a combination of genetic skin-barrier defects and immune dysregulation. • **Atopic triad** — eczema frequently co-occurs with asthma and allergic rhinitis, collectively known as the atopic triad, suggesting a shared immunological mechanism (IgE-mediated hypersensitivity). • It is the most common chronic skin disease in children, affecting approximately 20% of children worldwide, though many outgrow it. • 💡 Option B (Liver) is wrong because liver inflammation is hepatitis; liver fibrosis is cirrhosis — both are entirely separate from skin conditions; Option C (Eyes) is wrong because eye conditions include conjunctivitis and trachoma; Option D (Lungs) is wrong because lung disorders include pneumonia and asthma, though asthma is related to atopy.