Clinical Conditions

Question 1

Hereditary Spherocytosis/Eliptocytosis

Answer 1

Autosomal dominant
Spectrum within RBC depleted by 50% 
Erythrocytes become more rounded (sphero) or rugby ball shaped (elipto) 
More prone to lysis and spleen removal
Results in haemolytic anaemia

Question 2

Myasthenia gravis

Answer 2

Autoimmune destruction of end plate ACh receptors
Less depolarisation through muscle fibre
APs less amplitude
Difficulty with contraction
Causes muscle fatigue and extreme weakness, exacerbated by exercise

Question 3

Familial hypercholesterolaemia

Answer 3

Defect in LDL receptor…

• Receptor deficiency - mutation prevents expression of LDL receptors
• Non-functional receptors - no binding of LDL
• Receptor binding normal - no interaction with coated pits, can’t form proper coated vesicles

Excess circulating cholesterol, deposited as tendon xanthomas, xanthelasmas or corneal arcus

Question 4

Pheochromocytoma

Answer 4

Noradrenaline secreting tumor of the chromaffin cells of the adrenal medulla
Detected by levels of VMA (end product of NA breakdown) in urine
Symptoms of excess sympathetic stimulation (sweating, tachycardia etc)
Treatment - alpha-methyl tyrosine (blocks biogenic amine synthesis by inhibiting tyrosine hydroxylase -> reducing levels of NA)

Question 5

Reitintis pigmentosa

Answer 5

Loss of function of rhodopsin GPCR
Progressive degeneration of vision due to rod cell damage
Genetically inherited

Question 6

Nephrogenic diabetes insipidus

Answer 6

Loss of function of V2 vasopressin (ADH) receptor 
Kidneys don't retain water 
Huge volumes of urine passed 
Dehydration and death 
Usually genetically inherited

Question 7

Familial male precocious puberty

Answer 7

Gain of function in luteinizing hormone receptor
Androgens produced in larger quantities more quickly
Can kickstart puberty from 2 years onwards
Short stature - epiphyseal growth plates close earlier

Question 8

Asthma

Answer 8

Bronchoconstriction - shortness of breath, wheezing etc.
Release of inflammatory mediators (histamine) in response to allergen/irritant
Bronchi parasympathetically driven by M3 receptors (Gq-> PLC -> Ca2+ release -> constriction)
B2 adrenergic agonists given to cause bronchodilation
Don’t use muscarinic antagonists as they aren’t specific

Question 9

Hypertension

Answer 9

> 140/90
Leads to ischaemic heart disease
Influenced by baroreceptor reflex (short term) and renin-angiotensin-aldosterone system (long term)

Question 10

Thyrotoxicosis

Answer 10

Results from hyperthyroidism
T4 upregulates no. of adrenoceptors present
Increased heart rate through B1 receptors
Increased sweating through sympathetic innervation
Short term - non-specific beta adrenoceptor antagonist (propranolol)
Long term - carbimazole