20th February 2025

A 54-year-old man presents with breathlessness and haemoptysis.

A 54-year-old man presents with breathlessness and haemoptysis. He has also had a few weeks to months of malaise, weight loss, generalised joint aches and intermittent fevers. He has no significant medical history and does not have a smoking history.

On the urine dipstick, he has 3+ blood and 2+ protein. His initial bloods are shown below:

Eosinophils 0.3 x 109/L (normal: 0.1-0.4 x 109/L)

Creatinine 450 micromol/L (normal: 55 – 120 micromol/L)

CRP 98 mg/L ( normal: < 10 mg/L)

His chest radiograph shows bilateral infiltrates and a high-resolution CT thorax show alveolar haemorrhage and no evidence of malignancy. A non-contrast CT of the urinary tract shows no obstruction and normal-sized kidneys.

A subsequent renal screen shows:

c-ANCA: Positive

p-ANCA: Negative

ANA and ENA: Negative

C3/C4: Normal

anti-GBM antibodies: Negative

What is the most likely diagnosis?

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