Interstitial lung disease (ILD) may be a diagnostic conundrum and a therapeutic puzzle at all ages, but especially so in paediatric practice. First, because it is rare in children. The prevalence in the adult population was estimated in one study as ∼70 per 100,000 1, but the limited paediatric data in the literature would suggest it is at least two orders of magnitude less common in children. For example, a survey from the UK estimated the prevalence at 0.36 per 100,000 2. Even allowing for the likelihood of under-diagnosis and under-reporting, this is still a very rare group of conditions in children. Secondly, there is far greater diversity in the types of disease found in children. Newly described entities include pulmonary interstitial glycogenosis (PIG) 3, neuro-endocrine cell hyperplasia of infancy (NEHI) 4 and the disorders of surfactant metabolism (discussed in detail below). Usual interstitial pneumonia (UIP), relatively common in adults, is very unusual indeed in children. Thirdly, paediatric ILD occurs in the context of normal lung development; indeed the majority are diagnosed in the first year of life 2, 5, at a time when rapid alveolar multiplication is taking place 6. This combination of rarity, diversity and context has meant that much of what is known about paediatric ILD is merely anecdotal. Such studies as have been carried at involved small numbers of patients, with no randomised controlled trials to guide treatment. However, two important themes are emerging: the two-way cross-fertilisation of ideas between adult and paediatric pulmonologists; and the need for international collaboration. The European Respiratory Society (ERS) has an unrivalled track record in both areas, and now is the perfect opportunity to make headway in both adult and paediatric ILD.
The super-hot topic of surfactant metabolism perfectly illustrates the overlap between the …