Question: What is (are) multiple cutaneous and mucosal venous malformations ?
Answer: Multiple cutaneous and mucosal venous malformations (also known as VMCM) are bluish patches (lesions) on the skin (cutaneous) and the mucous membranes, such as the lining of the mouth and nose. These lesions represent areas where the underlying veins and other blood vessels did not develop properly (venous malformations). The lesions can be painful, especially when they extend from the skin into the muscles and joints, or when a calcium deposit forms within the lesion causing inflammation and swelling. Most people with VMCM are born with at least one venous malformation. As affected individuals age, the lesions present from birth usually become larger and new lesions often appear. The size, number, and location of venous malformations vary among affected individuals, even among members of the same family.
Source: GHR

Question: What are the genetic changes related to multiple cutaneous and mucosal venous malformations ?
Answer: Mutations in the TEK gene (also called the TIE2 gene) cause VMCM. The TEK gene provides instructions for making a protein called TEK receptor tyrosine kinase. This receptor protein triggers chemical signals needed for forming blood vessels (angiogenesis) and maintaining their structure. This signaling process facilitates communication between two types of cells within the walls of blood vessels, endothelial cells and smooth muscle cells. Communication between these two cell types is necessary to direct angiogenesis and ensure the structure and integrity of blood vessels. TEK gene mutations that cause VMCM result in a TEK receptor that is always turned on (overactive). An overactive TEK receptor is thought to disrupt the communication between endothelial cells and smooth muscle cells. It is unclear how a lack of communication between these cells causes venous malformations. These abnormal blood vessels show a deficiency of smooth muscle cells while endothelial cells are maintained. Venous malformations cause lesions below the surface of the skin or mucous membranes, which are characteristic of VMCM.
Source: GHR