Recurrent renal stonesBMJ 2011; 343 doi: https://doi.org/10.1136/bmj.d5957 (Published 21 September 2011) Cite this as: BMJ 2011;343:d5957
This week’s question is on recurrent nephrolithiasis and is taken from the onExamination revision questions for the MRCP Part 2 examination.
A 21 year old woman presents to the clinic after her fifth episode of nephrolithiasis in the past three years. She tells you that both her brother and father also suffer from renal stones.
On examination her blood pressure is 135/80 mm Hg. Physical examination is normal.
Haemoglobin: 12 g/dl (reference range 11.5-16.5)
White cell count: 6.4 × 109/L (4-11)
Platelets: 272 × 109/L (150-400)
Serum sodium: 138 mmol/L (135-146)
Serum potassium: 4.1 mmol/L (3.5-5)
Creatinine: 85 μmol/L (79-118)
Calcium: 2.89 mmol/L (2.20-2.67)
Parathyroid hormone: upper limit of normal range.
Which of the following is the most likely diagnosis?
A Familial hypocalciuric hypercalcaemia
B Primary hyperparathyroidism
C Increased concentrations of parathyroid hormone related protein because of underlying malignancy
D Secondary hyperparathyroidism
E Tertiary hyperparathyroidism
Answer A is the correct answer.
The strong family history points towards this autosomal dominant condition as being the most likely diagnosis. Most often it leads to asymptomatic elevated concentrations of serum calcium, although some patients with the condition may experience recurrent episodes of renal stones.
The inherited condition is caused by a mutation in the calcium sensing receptor gene, which encodes a calcium sensing receptor expressed in the parathyroid gland and kidneys. The perceived lack of calcium concentrations by the parathyroid leads to normal to high concentrations of parathyroid hormone and therefore hypercalcaemia.
For a free “question of the day” from onExamination, relevant to the MRCP Part 1 examination, go to www.onexamination.com/general-medicine/mrcp-part-1/question-of-the-day.
Cite this as: BMJ 2011;343:d5957