It is described a desquamative interstitial pneumonia diagnosed by open biopsy of the lung, in a nine-month-old infant. The disease began at about two-months-old, with underdevelopment and evolution to progressive respiratory insufficiency that finished with the exitus at nine-months-old, before the initiation of the treatment with steroid. It is commented the bad prognostic in young infants diagnosed during the first year of life, questioning the utility of separate the desquamative interstitial pneumonia of the usual interstitial pneumonia in infants less than one-year-old.