A combined vascular malformation involves two or more types of vessel abnormalities. Any of the four types of lesions may be combined:

• Capillary
• Venous
• Lymphatic
• Arteriovenous

Combined malformations are typically accompanied by overgrowth of soft tissues (skin, fat and muscle) and bones. However, patients may also have other skeletal abnormalities and undergrowth of the affected side. Most combined malformations involve limbs, but they can involve any area of the body.

While the precise cause of these lesions is unknown, they begin early in embryonic life and are thought to be caused by an error in the formation of multiple types of blood vessel channels in a particular anatomical area. Their occurrence is unrelated to drugs or medications that may have been taken during pregnancy or to environmental exposures that may have occurred at that time.

Combined lesions are generally evident upon physical examination, and larger combined lesions may be evident on prenatal ultrasonographic examination. The tissues involved and the extent of involvement is determined by magnetic resonance imaging (MRI), with special imaging sequences for arteries, veins, and lymphatics. Effects on bone growth are determined by plain X-rays.

Complications vary with the particular vessels involved in the malformation. For example, a capillary-lymphatic-venous malformation is associated with minor to major overgrowth of soft tissue and underlying bones. The lymphatic vesicles often bleed and the lymphatic components increase the possibility of infection. The venous components can cause pain, swelling, heaviness of the extremity, and abnormalities of the coagulation system.

The major complication of capillary-arteriovenous-lymphatic malformations is the shunting of blood through the abnormal arteriovenous connections. This causes pain, skin breakdown, and can lead to congestive heart failure. Extremity overgrowth is also a concern.

The type of treatment required for combined malformations depends upon the channels involved. All patients require evaluation by a wide range of specialists, and treatment strategies require close interdisciplinary collaboration.

Extremity lesions are often treated with supportive approaches such as limb elevation and the use of compression garments. Lesions that are complex may require surgical excision, sclerotherapy, embolization, and/or an overall treatment strategy that combines a variety of approaches used over time.