1 Alveolar epithelial cell development and function abnormalities: Undermining the stability of the alveolar capillaries, causing recurrent bleeding, but the cause of abnormal epithelial cells is not clear.

2 Abnormal elastic fibers in the lung: Abnormal elastic fibers acidic mucopolysaccharides, weakening blood vessel wall and expansion.

3 Milk allergy: Some children with milk skin test was positive in the serum antigen found in cow's milk precipitin reaction . Disable milk , the clinical symptoms disappear. But milk allergy can not explain all of the children sickness.

4 Organophosphate insecticides: Cassimos found that 80 percent of children grow in rural areas, they have poor economic conditions, less dietary protein; 50% of children have a continuing history of exposure to organic phosphorus pesticides. Cassimos think certain pesticides may induce the disease in children, more precise basis requires further investigation confirmed.

5. Genetic factors: Patients with the disease have something to do with their parents inbreeding, brothers, twins disease. So it can be considered to have relation to genetic factors, but no gene confirmed.