NORD gratefully acknowledges Subahari Raviskanthan, MD, Neuro-Ophthalmology Fellow and Andrew G. Lee MD, Chair, Blanton Eye Institute, Houston Methodist Hospital, for assistance in the preparation of this report.
Wyburn-Mason syndrome is a rare nonhereditary disorder that is present at birth (congenital). Affected infants have arteriovenous malformations (AVMs), which are developmental abnormalities affecting the blood vessels, specifically the arteries, veins and capillaries. Arteries typically carry oxygen-rich blood from the heart to body cells, while veins transport oxygen-deficient blood to the heart and lungs for the exchange of oxygen and carbon dioxide. The network of very tiny blood vessels (capillaries) that normally connects arteries and veins may be absent and the arteries and veins may be directly linked together forming a malformation. Without the capillaries, there can be damage to the walls of the arteries and veins, causing abnormal and high blood flow and leakage, and lack of blood flow further downstream. Larger AVMs may consist of a tangled mass of abnormal or malformed blood vessels (the nidus). AVMs associated with Wyburn-Mason syndrome are usually found in the eyes (retina) and brain. The exact cause of Wyburn-Mason syndrome is unknown, although it is hypothesized that during early development, the precursor cells to blood vessels have abnormal movement (migration) causing abnormal development later.
The disorder is named for the investigator (Dr. R. Wyburn-Mason) who extensively described the disease entity in 1943. It is also referred to as Bonnet-Dechaume-Blanc syndrome after 3 investigators who identified AVMs in the face, retina and brain in 1937.
Wyburn-Mason syndrome is sometimes grouped with the phakomatoses or neurocutaneous syndromes. This broad group of disorders is characterized by masses or tumors that may grow in the brain, spinal cord and other organs. In children, skin lesions are also prominent. Unlike other so-called phakomatoses, Wyburn-Mason syndrome rarely has skin abnormalities.
The symptoms associated with Wyburn-Mason syndrome vary greatly among affected individuals based upon the specific number and location(s) of associated arteriovenous malformations. Affected infants may have abnormalities affecting the eyes, central nervous system and, in rare cases, the skin.
In Wyburn-Mason syndrome, AVMs may range from absence of the capillaries to the presence of large masses of widened, twisted, tangled blood vessels known as a racemose hemangioma. Absence of capillaries results in the abnormal, direct connection of the arteries to the veins. This abnormal connection can result in excessive blood flow and subsequently inadequate blood flow (ischemia) further downstream.
AVMs in Wyburn-Mason syndrome often affect the thin layer of nerve cells that lines the back of the eyes (retina). In some cases, an AVM may extend into the eye socket (orbit) or brain. The specific symptoms associated with an ocular AVM vary depending upon the exact location and extent the abnormality. Small AVMs affecting tiny blood vessels may not cause any symptoms (asymptomatic) and may be difficult to detect. Large AVMs such as a racemose hemangioma may cause significant loss of vision, usually from lack of blood flow to the retina (retinal ischemia).
Additional eye abnormalities may occur in some individuals with Wyburn-Mason syndrome including pressure on the eyeball so that the eyes bulge forward (proptosis), drooping of the upper eyelid (blepharoptosis), difficulty moving the eyes (ocular motility disorders), abnormally widened (dilated) blood vessels of the thin membrane that covers the outer surface of the eye (conjunctiva), and nerve paralysis (palsies).
AVMs of the central nervous system may not cause any symptoms (asymptomatic) or can cause severe symptoms. Although AVMs are present at birth, in many cases they may not cause symptoms until the second or third decade of life or even later. Neurological symptoms associated with Wyburn-Mason syndrome include severe headaches, vomiting, seizures, paralysis (palsy) of various cranial nerves and neck stiffness (nuchal rigidity). Spontaneous bleeding (hemorrhaging) of these lesions can lead to the sudden onset of symptoms. If the bleeding is severe, it can cause partial or full paralysis of one side of the body (hemiparesis or hemiplegia) or even death.
In rare cases, the skin may be involved in Wyburn-Mason syndrome including the formation of small bumps or clusters of blood vessels (angiomas) on the face. If the jaw bones are involved, dental procedures can lead to excessive bleeding. Other areas of the body may also develop AVMs including the lungs or the kidneys or other bones and muscles.
The exact cause of Wyburn-Mason syndrome is unknown. It is considered a developmental abnormality characterized by AVMs. No specific genetic abnormality or hereditary tendencies have been identified. The specific, underlying mechanism(s) that cause AVMs in Wyburn-Mason syndrome are not known. However, they are thought to result from abnormalities of blood vessel development during embryonic or fetal growth.
Wyburn-Mason syndrome is an extremely rare disorder that appears to affect males and females in equal numbers. The incidence or prevalence rates of Wyburn-Mason syndrome in the general population are unknown, with less than 100 cases reported.
A diagnosis of Wyburn-Mason syndrome may be made based upon a thorough clinical evaluation, a detailed patient history, and identification of characteristic findings, especially ocular findings. Imaging studies such as a computed tomography (CT) scan or magnetic resonance imaging (MRI) may be performed to detect potentially dangerous central nervous system (CNS) malformations. During CT scanning, a computer and x-rays are used to create a film showing cross-sectional images of certain tissue structures. An MRI uses a magnetic field to produce cross-sectional images of particular organs such as the brain. Dye (contrast) can be injected into blood vessels and X-ray images taken (cerebral angiogram) to see AVMs in the brain, or photos can be taken of the back of the eye (fluorescein angiogram) to detect the AVM in the eye. The combination of AVM in the brain and eye make the diagnosis of Wyburn Mason syndrome.
No specific treatment for Wyburn-Mason syndrome exists. Treatment is directed toward the specific symptoms that are apparent in each individual. Some AVMs may not require treatment, especially retinal lesions which usually remain stable. If lesions in the eyes cause bleeding (hemorrhaging) in the retina or the clear, jelly-like substance that fills the middle of the eye (vitreous), laser treatment or the use of extreme cold to destroy abnormal tissue (cryosurgery) may be performed in an attempt to control the bleeding. Surgical removal of the vitreous (vitrectomy) has been performed in some cases if bleeding is persistent, although surgery is controversial.
AVMs inside the cranial compartment of the skull (intracranial AVMs) may be treated in one of three ways (surgical, radiation, embolization). Many intracranial AVMs may be completely removed with a surgical procedure. Some intracranial AVMs, because of their location within the brain, are not considered good candidates for surgical resection. For these AVMs treatment with radiation should be considered. Radiation is delivered to the precise location of the AVM by a procedure called radiosurgery. Several different forms of stereotactic radiosurgery may be used including Linac, Gamma Knife, Cyberknife, or others. Finally, endovascular embolization or occlusion of the abnormal arteries by a catheter technique can be considered in certain cases. Referral to a neurosurgeon is essential in order to best define the most appropriate treatment for any given AVM.
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