Lymphoid interstitial pneumonitis and hypogammaglobulinemia in children.

Lymphoid interstitial pneumonitis is an uncommon process, and an association with hypogammaglobulinemia in children is rare. Three patients, a 10-yr-old boy (Patient 1), a 17-yr-old girl (Patient 2), and a 13-yr-old boy (Patient 3) were evaluated for progressive interstitial pneumonitis and hypogammaglobulinemia. At presentation, symptoms or signs of lung disease had been present for 9, 6, and 1.5 yr and consisted of severe exertional dyspnea asymptomatic pneumonitis on roentgenogram, and mild exertional dyspnea, respectively. Serum immunoglobulin deficiencies were variable with IgG and IgA being depressed in all patients and IgM being within normal limits in Patient 2. In vitro neutrophil function and T lymphocyte number and mitogen responses were normal. Measurement of in vitro immunoglobulin production suggested a primary B lymphocyte dysfunction. Pulmonary function testing revealed restrictive lung disease in Patient 1, arterial hypoxemia in Patients 1 and 2, and increased alveolar-arterial oxygen differences in all patients. Microscopic examination of lung specimens from each patient revealed diffuse lymphoid parenchymal infiltration with formation of follicles with occasional germinal centers, varying degrees of fibrosis, and negative examinations for viruses, bacteria, and fungi. The factors responsible for the cessation of antibody production and for the striking lympho-proliferative process seen in these patients remain to be identified.