INTERSTITIAL LUNG DISEASE DIAGNOSISTo make a diagnosis of ILD, routine investigations should include a CBC with differential, an ESR and other routine biochemistries.
An EKG and an echo are necessary to rule out pulmonary hypertension. Pulmonary function testing can be undertaken in older children, though infant pulmonary function testing is now becoming more widely available. Pulmonary functions should be consistent with a restrictive pattern, though some airflow limitation can occur.
Nasopharyngeal swabs, sputum if available, HIV serology, and a Mantoux test are all part of a baseline work-up.
Immunologic investigations are suggested, including IgE, vaccine titres, T and B cell subsets, and complement, as is a minimal rheumatologic screen (ANA, ACE, ANCA).
Sweat chloride, alpha-1 antitrypsin, pH probing, and urinalysis may also be indicated.
In terms of imaging, chest radiography and high resolution computed tomography are essential to the diagnosis, though sinus films and an upper GI study may also be helpful.
The definitive diagnosis is, of course, made on biopsy. The gold standard of open lung biopsy yields a diagnosis in 80% of cases, though thorascopic biopsy is now becoming an option. A transthoracic biopsy is preferred to a transbronchial biopsy for diagnosis where possible. BAL, with a diagnostic yield of 30%, is often of more use in ruling out an infectious process, proteinosis, or hemosiderosis than in diagnosing ILD. BAL is of particular use in the immunocompromised population.
INTERSTITIAL LUNG DISEASE PROGNOSIS
The prognosis for all ILD in infancy is unknown, as the etiologies are quite variable. An overall mortality rate of 16-20% has been quoted by most. There is no good correlation between the severity of the histologic changes on biopsy with response to anti-inflammatory treatment, and there are reported cases of ILD that have undergone spontaneous resolution.
INTERSTITIAL LUNG DISEASE TREATMENT
Treatment of ILD includes supportive management, such as oxygen, support of growth, bronchodilators and appropriate vaccine usage. Corticosteroids are the mainstay of treatment, and available strategies include daily dosing (1-2 mg/kg/d) or monthly pulses. Approximately 40% of children with ILD will be steroid responsive.
Adjuncts or alternatives tried to date include cyclophosphamide, azathioprine and hydroxycholorquine and chloroquine. Hydroxychloroquine is preferred to its predecessor chloroquine because it has less ocular toxicity, though both can induce liver toxicity.
The mechanism of action in treating ILD is unknown, but hypothesized to be through an anti-inflammatory effect. Transplant is a final alternative.
This case was chosen to illustrate the difficulties facing the pediatric respirologist in discerning a rare disorder from amongst a host of uncommon diagnoses. As new techniques emerge to elucidate the mechanisms underlying these various processes, the nomenclature and classification of these entities are changing. These changes, in addition to the scarcity of data in the pediatric population in comparison to the adult literature, make it very challenging to provide a family with a prognosis, should a diagnosis actually be confirmed. A structured approach can be of assistance in forming a differential diagnosis and guiding a rational approach to investigations which produce the most yield in an efficient manner.
Bibliography on the following page.