Good's syndrome: an uncommon cause of therapy-resistant diarrhoea

Diarrhoea is a common symptom for which the aetiology will be straightforward in many cases. However, when a common aetiology is not found, the wide variety of other options can feel like finding a needle in a haystack. In this case report, we describe a patient who was referred to our centre with therapy-resistant, secretory diarrhoea, which was the presenting symptom of Good's syndrome, a rare form of adult-onset immunodeficiency associated with thymoma. The conclusions from this case report give direction for 'finding the needle' and contribute to a focused approach to patients who present with therapyresistant diarrhoea.