 Combined Vascular Malformation
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The term "combined" means that the vascular malformation involves more than one type of channel abnormality and tissue. Sometimes the word "syndrome" is attached--meaning literally a "running together" of different abnormalities believed to have a common cause. Many vascular malformations are known by the names of the physicians given credit for the first or the most complete description of the disorder. Most physicians believe these proper names should no longer be used because they are so often misused and are misleading. Combined vascular malformations typically are usually accompanied by overgrowth of soft tissues and bones.
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The precise cause is unknown. The theory is that a mutation occurs (after fertilization) in a primitive cell leading to formation of different types of blood vessel channels in a given region. No known food, medication, or activity during pregnancy can cause a vascular malformation.
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They begin early in embryonic life; sometimes they can be seen on prenatal ultrasonography. They are congenital, meaning present at birth.
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They often involve a limb, sometimes more than one limb. The perineum and trunk can also be affected.
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The two most common and well-known forms are Klippel-Trenaunay syndrome and Parkes Weber syndrome. Unfortunately, these two are often confused with one another. Both present as an overgrowth of soft tissue and bone, usually in a limb. In other combined disorders, e.g. Maffucci, Bannayan-Riley-Ruvalcaba, or Proteus syndrome, the vascular anomaly may be a minor component.
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Klippel-Trenaunay syndrome is a combined CLVM; it is a slow-flow vascular anomaly. It is characterized by a geographic capillary stain (CM), venous anomalies of the superficial and deep system, lymphatic abnormalities, and overgrowth (but sometimes undergrowth) of the soft tissues and bones. The capillary stain usually develops tiny dome-like vesicles. The anomaly can involve either an upper/lower limb, trunk, or any combination.
Parkes Weber syndrome is combined CAVM; it is a fast-flow condition. It is characterized by a geographic flat, pink, warm, stain with underlying multiple arteriovenous connections in skin and muscle, and overgrowth of the extremity.
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CLVM is associated with minor to major overgrowth of both soft tissue and underlying bones. The capillary-lymphatic vesicles often bleed. The lymphatic components increase the possibility of infection of the tissues. The venous components cause pain and heaviness of the extremity and can form clots that can migrate to the lungs.
The major complication of CAVM (Parkes Weber syndrome) is shunting of blood through the abnormal arteriovenous connections, causing pain, skin breakdown, and high output congestive heart failure. Overgrowth of the extremity, in girth and length, are also concerns.
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Often a combined anomali can be seen on prenatal ultrasonographic examination; they are obvious at birth. The extent and tissues involved are determined by magnetic resonance imaging (MRI) with special sequences for arteries, veins, and lymphatics.
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Patients should be evaluated by members of an experienced interdisciplinary vascular anomalies team. No single specialist can manage these problems, as interventional techniques and surgical procedures are needed. Other specialists that may need to be involved are dermatologists and hematologists.
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These anomalies are caused by localized or generalized errors in the normal molecular pathways that regulate the formation of blood and lymphatic vessels. The keys to understanding these abnormalities lie in the basic sciences of molecular biology and molecular genetics. Investigators are currently probing the genes and molecules that regulate the formation and growth of blood/lymphatic vessels. Understanding the genes that control these molecular events will surely result in novel therapies for vascular malformations.
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