Hypoproteinemia (or hypoproteinaemia) is a condition where there is an abnormally low level of protein in the blood. There are several causes and all result in edema once serum protein levels fall below a certain threshold.
Nutritional hypoproteinemia is due to severe limitation of protein intake in the diet. An example of nutritional hypoproteinemia is Kwashiorkor, a type of protein energy malnutrition affecting young children.
Decreased serum protein decreases the osmotic pressure of the blood, leading to loss of fluid from the intravascular compartment, or the blood vessels, to the interstitial tissues, resulting in edema. This is termed as Hypoproteinemia.