by Anne Marie Helmenstine, Ph.D. Updated June 13, 2014. Definition: A molecular orbital is an orbital or wavefunction of a molecule's electron. Electrons around a molecule can be associated with more than one atom and are often expressed as a combination of atomic orbitals.
Hereditary angioedema is a disorder characterized by recurrent episodes of severe swelling (angioedema). The most common areas of the body to develop swelling are the limbs, face, intestinal tract, and airway. Minor trauma or stress may trigger an attack, but swelling often occurs without a known trigger.
Angioedema is caused by an allergic reaction to something you've eaten, an insect bite, pollen allergies, or a medication you've taken. It causes a swelling of the lips, face, and tongue, which usually occurs rapidly. It can also sometimes be accompanied by redness or bumps (hives). Due to the swelling, you may have difficulty talking. Angioedema can also cause swelling of the airway and difficulty breathing, which may be life-threatening.