Another gene of interest but less studied is ADAM33 which encodes a disintegrin and metalloproteinase domain-containing protein 33; this protein family is related to cellular adhesion, signaling, and proteolysis; variants in this gene have been principally associated with a higher risk for developing asthma, bronchial hyperreactivity, and COPD [15,16]. Here, ADAM33 is linked to chronic obstructive pulmonary disease.