Serum histamine-releasing activity in a patient with idiopathic pulmonary haemosiderosis

Background: idiopathic pulmonary haemosiderosis (IPH) is a rare disorder characterized by intermittent, diffuse alveolar bleeding. The pathogenesis of the diseases is unclear, although an association with milk or gluten hypersensitivity has been described, and an immune-mediated damage of alveolar capillaires has been suggested. A previous report showed the release of histamine after cow's milk intake in a newborn with cow's milk intolerance and IPH. Methods and results: here, we report the detection of serum histamine-releasing activity (HRA) in a 30-year-old woman with IPH. The serum taken during an active phase of the disease induced histamine release from basophils of two normal donors; conversely, when the patient was receiving prednisone and azathioprine, and the disease was in remission, the serum HRA was reduced. Serum fractions with a MW lower than 100 kDa displayed an enhanced HRA; in contrast, serum fractions with MW above 100 kDa were not able to induce histamine release, suggesting that the activity was due to a cytokine and not to an immunoglobulin. Conclusions: the detection of serum HRA provides futher evidence that the immune system is activated in the course of IPH and supports an immunologic basis for the alveolar capillary damage, which is responsible for alveolar bleeding.