Interstitial lung disease is very rare in children, with only 6-8 cases per million population in the U.K. ILD is thought to develop as an inflammatory, immune response which damages the gas-exchanging part of the lung (alveoli).The resulting chronic inflammation is associated with varying degrees of fibrosis (scarring) within and around the alveoli - thought to be the result of abnormal healing; this interferes with oxygen transfer into the blood. The processes involved in the development of ILD in children are probably different from those in adults, although, as in adults, some have a known cause and some do not. Evidence is emerging that some types of ILD, of previously unknown cause, may be associated with genetic mutations responsible for deficiencies of surfactant proteins B and C. The major difference in ILD in children compared with adults seems to be that it generally responds better to treatment; this may be due to continuing lung growth and development in children.
Clinical presentation in children is variable; Respiratory distress and failure to thrive are common in infants while in older children breathlessness is the norm. The outcome is very variable and cannot be predicted by Chest X-ray or CT lung scan appearances. However, there is some relationship between severity of initial presentation and outcome. The diagnosis is generally made with a CT lung scan (high resolution) and by taking a sample of lung tissue (lung biopsy).
The classification of causes of ILD in childhood is rather confusing; sometimes it is classified by the appearances under the microscope and sometimes by whether there is a known cause or association. Here is a list of the names of these different types
ILD of unknown cause
- Desquamative interstitial pneumonia
- Ideopathic fibrosing alveolitis (usual interstitial pneumonia)
ILD of known cause
- Infectious interstitial pneumonia (e.g. cytomegalovirus or Epstein-Barr virus)
- Reaction to a drug (e.g. nitrofurantoin, gold,azathiaprine, methotrexate etc) or radiation
- Reaction to inhaled environmental particles (silica, asbestos, talc etc), fumes (sulphuric acid), gases (Chlorine, ammonia) or organic dust
- Lymphocytic interstitial pneumonia
- Alveolar proteinosis
- Pulmonary haemosiderosis
- Pulmonary lymphangiomatosis (LAM)
- Recurrent aspiration + gastric reflux
- Familial dystautonomia
ILD associated with a general disease (50% cases)
- Autoimmune diseases (e.g. juvenile rheumatoid arthritis, Systemic Lupus Erythematosis, Diabetes, Amyloisosis, Histiocytosis X, Goodpasture’s syndrome etc)
- Vasculitis (inflammation of blood vessels e.g. Wegener’s granulomatosis, Polyarteritis, Churg-Strauss syndrome)
- Cancers
- Liver or bowel disease
- Metabolic diseases
- Skin disease - neurofibromatosis
Treatment is usually directed at the cause, if known. If it is unknown, courses of methylprednisolone ( a type of steroid), followed by long term steroid tablets +/- hydroxychloroquine are recommended.
15% children with this disease die from it but most of the others make a full recovery. A few are left with breathing difficulties, needing long term oxygen treatment.
