12th January 2024

A 62-year-old woman is taking co-trimoxazole daily as prophylaxis, given a previous admission with pneumocystis pneumonia.

A 62-year-old woman is taking co-trimoxazole daily as prophylaxis, given a previous admission with pneumocystis pneumonia. Her most recent blood tests came back as follows:

• Hb 128 g/L (115-165)
• MCV 112 fL (80-100)
• Reticulocyte count 1.2% (0.2-2)
• WCC 8.2 x 10*9/L (4.0-11.0)
• Serum sodium 137 mmol/L (133–146)
• Serum potassium 4.1 mmol/L (3.5–5.3)
• Urea: 6.3 mmol/L (2.5 – 7.8 mmol/L)
• CRP 38 mg/L (<10)

What is the most likely cause for her anaemia?

Select the SINGLE most appropriate option from the list below. Select ONE option only.