MRCP Part 1 Clinical Sciences

Question 1

A 45-year-old man presents with muscle weakness and hypokalaemia. His arterial blood gas shows metabolic alkalosis. Which hormone, if produced in excess, is most likely responsible?

Accepted Answer

Aldosterone

Answer

Excess aldosterone (Conn's syndrome) causes sodium retention and potassium excretion, leading to hypokalaemia and metabolic alkalosis. This is a classic presentation of primary hyperaldosteronism.

Question 2

Which immunoglobulin class is found in highest concentration in normal human serum?

Accepted Answer

IgG

Answer

IgG constitutes approximately 75-80% of serum immunoglobulins and is the most abundant antibody class in blood. It crosses the placenta and provides passive immunity to neonates.

Question 3

A patient with chronic kidney disease has a corrected calcium of 1.9 mmol/L and phosphate of 2.1 mmol/L. Which is the most likely underlying mechanism?

Accepted Answer

Reduced renal 1-alpha-hydroxylase activity

Answer

In CKD, the kidneys cannot convert 25-hydroxyvitamin D to its active form (1,25-dihydroxyvitamin D) due to reduced 1-alpha-hydroxylase activity. This leads to decreased calcium absorption, hypocalcaemia, and hyperphosphataemia from reduced renal phosphate excretion.

Question 4

Which type of hypersensitivity reaction is responsible for Goodpasture's syndrome?

Accepted Answer

Type II (cytotoxic)

Answer

Goodpasture's syndrome is a type II hypersensitivity reaction where autoantibodies target the alpha-3 chain of type IV collagen in glomerular and alveolar basement membranes, causing glomerulonephritis and pulmonary haemorrhage.

Question 5

A 30-year-old woman has a serum sodium of 118 mmol/L, serum osmolality of 260 mOsm/kg, and urine osmolality of 550 mOsm/kg. She is clinically euvolaemic. What is the most likely diagnosis?

Accepted Answer

Syndrome of inappropriate ADH secretion (SIADH)

Answer

SIADH presents with hyponatraemia, low serum osmolality, and inappropriately concentrated urine (>100 mOsm/kg) in a euvolaemic patient. Psychogenic polydipsia would show dilute urine, and Addison's would typically show hypovolaemia.

MRCP Part 1 Practice Test

MRCP Part 1 Practice Test

MRCP Part 1 Clinical Sciences