Hereditary Hemorrhagic Telangiectasia (HHT)
A genetic disorder called hereditary hemorrhagic telangiectasia (HHT) or Rendu-Osler syndrome is characterized by multiple, small arteriovenous lesions that can occur in the skin, mucous membranes (mouth, nose, and gastrointestinal tract), lungs, liver, brain, and other sites.
Three genes are known to cause this condition, all of which result in the dysfunction of cell receptors. In HHT, arteriovenous malformations usually present with telangiectasia (permanent widening of groups of superficial capillaries and tiny veins) of the skin and mucous membranes. Bleeding typically occurs during and after puberty, and treatment is aimed at minimizing bleeding. In cases of nosebleeds, laser treatment of the nasal septum (thin membrane between nostrils) can be quite helpful. However, medical therapies with injectable agents such as Avastin are presently being used for nosebleeds.
Parkes-Weber syndrome involves diffuse arteriovenous malformations of a limb with overgrowth of the limb. These patients also may have lymphatic malformations. The affected limb usually has a capillary malformation involving skin. The heart may be affected secondary to increased blood flow in the involved area of the body. If untreated, this can result in an enlarged heart and eventually in heart failure.
MRI and MRA are the most appropriate diagnostic techniques. Some patients also must undergo an echocardiogram to monitor the status of the heart.
Treatment may include embolization and, in some patients, surgical procedures.
CLOVES syndrome involves arteriovenous malformations, which are often rare and aggressive when involved with CLOVES. These AVMs may also be found as a high-flow aggressive spinal lesion, which can cause serious neurological deficits or paralysis.
CLOVES is a congenital syndrome that includes lipomatous tissue overgrowth, vascular malformations, epidermal nevi, and skeletal or spinal abnormalities. Most children diagnosed with CLOVES do not have all of these signs, but rather a combination of abnormalities. Therefore, treatment of this condition varies greatly based upon what abnormalities are involved.