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Page 7 / Case 04.03

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These slides show features typical of desquamative interstitial pneumonitis, or DIP.
The airspaces and bronchi are filled with histiocytes, and the alveoli are lined by hyperplastic type 2 pneumocytes. The trichrome stain shows widening of the interstitium by mesenchymal cells, and immunohistochemistry staining is positive for CD 68 and vimentin. Stains for surfactant A and B were normal. Arterial architecture was normal, and all cultures sent from the biopsies were negative.

SUMMARY OF TREATMENT

After the results of his biopsy were known, treatment with methylprednisolone at a dose of 1 mg/kg/day was initiated. While still in hospital, he continued to deteriorate, requiring increasing amounts of oxygen, and had a respiratory rate of 110-120. He was then given two pulses of steroid in sequence, and after only minimal improvement, was started on hydroxychloroquine. Though all viral screening studies were negative initially, on culture he was subsequently found to be parainfluenza positive. After slow improvement, he was discharged and followed monthly, with pulse steroid courses over the next six months.

Now at the age of 10 months, he is steroid-free, with stable oxygen requirements of 0.5 L, and a respiratory rate in the 40√Ęs. He is growing well, and is developmentally appropriate. His serum has been sent for surfactant protein studies, but no result is as yet available. Future plans include a repeat CT chest at the age of 1 year, with possible weaning of his hydroxychloroquine base.

OVERVIEW OF INTERSTITIAL LUNG DISEASE (ILD) IN INFANTS

Interstitial lung disease is comprised of over 100 different entities, including conditions with abnormal pulmonary vasculature, abnormal lymphatics, small airways, surfactant protein deficiencies, and other idiopathic forms in common with adults.

The term "interstitial lung disease" is a misnomer, because these processes often involve alveoli and distal airways as well as the interstitium. The more descriptive term "chronic diffuse infiltrative lung disease" has instead been suggested.

ILD was first described in adults by Leibow and Carrington in 1968, and was made up of four main classifications: usual interstitial pneumonitis (UIP), desquamative interstitial pneumonitis (DIP), lymphocytic interstitial pneumonitis (LIP) and bronchiolitis obliterans organizing pneumonia (BOOP). BOOP has since been reclassified, and the remainder of the classic forms are rare in children.

LIP is the most common classically described interstitial pneumonitis, but it has been found to be a form of lymphoproliferative disease and not truly a pneumonitis. Acute interstitial pneumonitis, also known as Hamman-Rich syndrome, is also seen in childhood. It is rapidly progressive ("honeycomb lung") with a mortality rate of 50%.


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