Clinical conditions

Question 1

Osteogenesis imperfecta

Answer 1

Mutation in col1A gene leads to defective collagen

Signs/symptoms:
Blue sclera
Brittle bones
Short stature
Hypermobile joints
Hearing loss

Question 2

Ricketts/osteomalacia

Answer 2

Vit D deficiency (ricketts in children, osteomalacia in adults)

Decreased mineralisation of bone due to poor calcium absorption
Also caused by Ca2+ or phosphate deficiency

Causes weakened/ soft bones (impaired growth in ricketts)

Question 3

Osteoporosis

Answer 3

Type 1 primary- lack of estrogen in post menopausal women/ in older men, causes decreased osteoclast function*
Type 2 primary- lack of estrogen/ androgen, increased osteoblasts activity*
Secondary- another cause e.g corticosteroids, immobilisation, malnutrition
Calcium quantity gives risk factor

Question 4

Achondroplasia

Answer 4

Short limb dwarfism
Mutation of FGF3 receptor gene

Fibroblast growth factor not present as normal hence abnormal endochondral ossification- shorter long bones

Question 5

Multiple sclerosis

Answer 5

CNS disease,
Loss of myelin sheath via T cell destruction, overgrowth of glial tissue
Symptoms: Spastic paralysis, muscle spasms, fatigue, loss of sensation

Question 6

Myasthenia Gravis

Answer 6

Autoimmune- antibodies directed against Ach receptors-
Leads to: reduced receptor number, reduced end plate invaginations hence reduced synaptic transmission

Symptoms: intermittent muscle weakness

Question 7

Duchenne muscular dystrophy

Answer 7

Mutation in dystrophin gene

Excess calcium enters cell, thus enters mitochondria, mitochondria swell+burst
Causes rhabdomyolysis- muscle replaced by adipose

Question 8

Cystic fibrosis

Answer 8

Mutation in CFTR gene, deficiency in chloride ion release from goblet cells that leads to sticky mucus being formed

Symptoms: blocked airways, blocked small bile duct, male infertility, salty crystalline sweat, thick non-motile stools

Question 9

Hyperthyroidism/ Graves’ disease

Answer 9

High T3+T4, low TSH

Negative feedback loop between T3+T4 and TSH

Question 10

Scurvy

Answer 10

Vitamin C deficiency
Vit C required to hydroxylation proline+lysine molecules in formation of procollagen
Leads to disrupted collagen formation- poor wound healing, impaired bone function

Question 11

Marfan’s syndrome

Answer 11

Expression of Fibrillin 1 gene is affected making elastic tissue abnormal.
Symptoms: abnormally tall, arachnodactyly, aortic rupture

Question 12

Haemolytic anaemia

Answer 12

Caused by glucose-6-phosphate dehydrogenase deficiency (enzyme that is part of pentose phosphate pathway)
Leads to NAD+ accumulation and Heinz bodies