Human Diseases — Set 4

Correct Answer: B. Vitamin B complex

• **Vitamin B complex** = a group of eight water-soluble vitamins whose deficiency disrupts skin-cell metabolism, triggering the inflammation and scaling seen in dermatitis. • **Niacin (B3) deficiency** — specifically causes pellagra, whose classic triad includes dermatitis, diarrhoea, and dementia. • Biotin (B7) and riboflavin (B2) deficiencies also produce skin-rash symptoms distinct from dermatitis caused by other nutrients. • 💡 Option A (Vitamin D) is wrong because its deficiency causes rickets/osteomalacia, not skin inflammation; Option C (Calcium) is wrong because calcium deficiency leads to bone and muscle disorders; Option D (Iron) is wrong because iron deficiency causes anaemia, not dermatitis.

Correct Answer: A. Chickenpox

• **Chickenpox** = caused by the Varicella-zoster virus (VZV), a member of the Herpesviridae family that spreads by respiratory droplets and direct contact with lesions. • **Latency and reactivation** — after primary infection (chickenpox), VZV lies dormant in nerve ganglia and can reactivate decades later as Herpes Zoster (Shingles). • The disease produces characteristic fluid-filled blisters (vesicles) in successive crops over 5–7 days, usually starting on the trunk. • 💡 Option B (Hepatitis) is wrong because it is caused by Hepatitis A/B/C/D/E viruses, not VZV; Option C (Rabies) is wrong because rabies is caused by the Rabies lyssavirus; Option D (Polio) is wrong because it is caused by the Poliovirus (Enterovirus genus).

Correct Answer: A. Liver

• **Liver** = in cirrhosis, healthy liver tissue is progressively replaced by fibrous scar tissue, severely impairing the organ's detoxification, protein-synthesis, and bile-production functions. • **Common causes** — chronic alcohol abuse, hepatitis B and C infections, and non-alcoholic fatty liver disease (NAFLD) are the leading triggers worldwide. • End-stage cirrhosis can cause portal hypertension, ascites, and hepatic encephalopathy, often requiring a liver transplant. • 💡 Option B (Heart) is wrong because cardiac scarring is called fibrosis or cardiomyopathy; Option C (Spleen) is wrong because the spleen may enlarge secondarily due to portal hypertension, but is not the primary site; Option D (Lungs) is wrong because lung fibrosis is a separate condition called pulmonary fibrosis.

Correct Answer: C. Kwashiorkor

• **Kwashiorkor** = a severe form of protein-energy malnutrition in which protein deficiency predominates even when caloric intake may be adequate, leading to oedema, pot-belly, and skin/hair changes in children aged 1–3 years. • **Distinguishing sign** — the hallmark oedema (fluid retention) differentiates Kwashiorkor from Marasmus, which involves total calorie-and-protein starvation and produces severe wasting without oedema. • The name originates from the Ga language of Ghana, meaning "the disease the child gets when the new baby is born" (displaced from breastfeeding too soon). • 💡 Option A (Scurvy) is wrong because it is caused by Vitamin C deficiency, not protein deficiency; Option B (Goitre) is wrong because it results from iodine deficiency affecting the thyroid gland; Option D (Rickets) is wrong because it is caused by Vitamin D / calcium deficiency affecting bone development.

Correct Answer: B. Rat flea

• **Rat flea** = specifically Xenopsylla cheopis (Oriental rat flea) transmits Yersinia pestis, the bacterium causing bubonic plague, when an infected flea bites a human after its rat host dies. • **Bubonic vs pneumonic** — the bubonic form (swollen lymph nodes called buboes) is flea-transmitted; once lung-infected, person-to-person spread occurs as pneumonic plague via respiratory droplets. • The Black Death pandemic of the 14th century, caused by bubonic plague, killed an estimated one-third of Europe's population. • 💡 Option A (Bedbug) is wrong because bedbugs (Cimex lectularius) are not known vectors of plague; Option C (Mosquito) is wrong because mosquitoes transmit malaria, dengue, and filaria — not plague; Option D (Louse) is wrong because lice transmit typhus (Rickettsia prowazekii), not plague.

Correct Answer: B. Teeth and Gums

• **Teeth and Gums** = Pyorrhoea (periodontitis) is a severe gum infection in which pus discharges from inflamed periodontal pockets, causing progressive destruction of the bone and tissue that support the teeth. • **Bacterial cause** — the condition is driven by anaerobic bacteria such as Porphyromonas gingivalis that colonise the subgingival plaque when oral hygiene is neglected. • Untreated pyorrhoea ultimately leads to tooth loss and has been linked to systemic conditions including cardiovascular disease and diabetes. • 💡 Option A (Brain) is wrong because brain infections are termed meningitis or encephalitis; Option C (Intestines) is wrong because intestinal infections are conditions like colitis or enteritis; Option D (Lungs) is wrong because lung-related pus conditions are called lung abscess or empyema.

Correct Answer: B. Eyes

• **Eyes** = Trachoma is a chronic conjunctivitis caused by Chlamydia trachomatis, where repeated infections gradually scar the inner eyelid, eventually turning the eyelashes inward (trichiasis) and abrading the cornea leading to blindness. • **Leading infectious cause of blindness** — Trachoma is the world's leading infectious cause of preventable blindness, responsible for visual impairment in millions, mainly in Africa and Asia. • The WHO's SAFE strategy (Surgery, Antibiotics, Facial cleanliness, Environmental improvement) is used to control trachoma globally. • 💡 Option A (Throat) is wrong because Chlamydia trachomatis targets the conjunctiva, not the throat; Option C (Skin) is wrong because skin-targeting Chlamydia infections are different serotypes causing lymphogranuloma venereum; Option D (Ears) is wrong because ear infections are caused by different bacteria such as Streptococcus pneumoniae.

Correct Answer: C. Diphtheria

• **Diphtheria** = the DPT (also DTP) vaccine is a combined vaccine protecting against three bacterial diseases: Diphtheria (caused by Corynebacterium diphtheriae), Pertussis (whooping cough), and Tetanus. • **Diphtheria mechanism** — the bacterium releases a potent exotoxin that forms a grey pseudomembrane in the throat, obstructing airways; the toxin can also damage the heart and nerves. • DPT is given as a series of 5 doses starting at 6 weeks under India's Universal Immunisation Programme (UIP). • 💡 Option A (Diarrhea) is wrong because diarrhoeal diseases are prevented by the Rotavirus vaccine, not DPT; Option B (Dengue) is wrong because dengue is a viral disease spread by mosquitoes and has its own separate vaccine (Dengvaxia); Option D (Diabetes) is wrong because diabetes is a metabolic/autoimmune disorder, not an infectious disease preventable by vaccination.

Correct Answer: D. Skeletal fluorosis

• **Skeletal fluorosis** = chronic ingestion of fluoride above 1.5 mg/L causes excess fluoride to accumulate in bones and joints, making them dense yet brittle — a condition called skeletal fluorosis that causes joint pain, stiffness, and deformity. • **Dental fluorosis** — lower levels of excess fluoride (1.5–4 mg/L) first manifest as dental fluorosis, producing white mottling and pitting on tooth enamel before bones are affected. • India has the highest number of fluorosis patients in the world, with over 20 states reporting endemic fluoride-contaminated groundwater. • 💡 Option A (Night blindness) is wrong because night blindness is caused by Vitamin A deficiency, not fluoride excess; Option B (Kidney stones) is wrong because kidney stones are mainly caused by excess calcium, oxalate, or uric acid; Option C (Anaemia) is wrong because anaemia results from iron, B12, or folate deficiency, not fluoride toxicity.

Correct Answer: D. Bird Flu

• **Bird Flu** = H5N1 is a subtype of Influenza A virus where H5 refers to haemagglutinin protein 5 and N1 to neuraminidase protein 1; it primarily infects birds but can cross to humans through close contact with infected poultry. • **High fatality in humans** — when H5N1 infects humans it has a case-fatality rate exceeding 60%, far higher than seasonal flu, making it a major pandemic preparedness concern. • The first confirmed human H5N1 cases were reported in Hong Kong in 1997 during a poultry outbreak. • 💡 Option A (Ebola) is wrong because Ebola is caused by the Ebola virus (Filoviridae family), not an influenza virus; Option B (Swine Flu) is wrong because swine flu is caused by H1N1, a different influenza subtype; Option C (COVID-19) is wrong because COVID-19 is caused by SARS-CoV-2, a coronavirus entirely unrelated to influenza.