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What are the signs of mild cystic fibrosis?

Q I understand cystic fibrosis can present in adults with a lesser phenotype, such as intractable sinusitis. How likely is this to occur?

A There are two main clinical presentations of mild CF in adults. The first is congenital bilateral absence of the vas deferens (CBAVD), causing obstructive azoospermia and presenting as male infertility. Most CBAVD cases have one 'severe' and one 'mild' mutation in the CFTR (CF transmembrane regulator) gene that causes CF.

When a detailed clinical history is taken from these men there is often a history of recurrent sinusitis with nasal polyps, perhaps with at least one lower respiratory tract infection. Chronic sinusitis is the most likely presenting complaint of mild CF in women (female reproductive tract malformations are not associated with CFTR mutation).

However, nasal polyps and sinusitis are common and mild CF is rare, particularly in fertile males.

CF mutation testing should therefore be offered to adults with chronic sinusitis and nasal polyps only if there is other suggestive history, such as pneumonia, male infertility, malabsorption, pancreatitis or family

history of CF. Molecular testing is available through regional DNA diagnostic laboratories.

David Fitzpatrick is

consultant in genetics at the

Royal Hospital for Sick Children, Edinburgh

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