• cilia
• Kartagener’s syndrome
• bronchiectasis
• chronic secretory otitis media
• neonatal respiratory distress
• infertility

All children cough, all children have runny noses, and most children are normal. In a child with a cough, an unexpected additional finding, for example rectal prolapse, should lead to a reappraisal of what at first sight may be a trivial symptom, and a new diagnosis such as cystic fibrosis (CF) may be made. The well known frequency of this disease, the ready availability of the sweat test in every hospital and the generally low threshold for its performance, should make diagnosis of CF straightforward. However, even CF, with all these favourable factors, is hardly a diagnostic success story; 10–15% patients are not diagnosed until adulthood.^1,2 It is not surprising therefore that a rarer condition such as primary ciliary dyskinesia (PCD), to which the only diagnostic clues may be a chronic moist cough and a runny or blocked nose, and for which diagnostic testing is not widely available, is often missed for a long time. What is depressing is that even a very unexpected finding, mirror image organ arrangement, frequently does not prompt a diagnostic review for many years,³ long after the child has suffered lasting damage.

The incidence of PCD in the white population is estimated to be 1 in 15 000, although it is higher in communities where first cousin marriages are common. In the white population⁴ there will be around 70 new cases born per year, and it is estimated that there are 3000 cases in the UK in total. By contrast, only around 150 cases are known to the UK PCD support group (personal communication). Even if this group is aware of only one tenth of known cases, the implication is that there are large numbers of undiagnosed patients. Does this matter, and, if it does, how …