Arteriovenous malformation is an abnormal connection between arteries and veins, bypassing the capillary system. This vascular anomaly is widely known because of its occurrence in the central nervous system (usually cerebral AVM), but can appear in any location. Although many AVMs are asymptomatic, they can cause intense pain or bleeding or lead to other serious medical problems.AVMs are usually congenital and belong to the RASopathies. The genetic transmission patterns of AVMs are incomplete, but there are known genetic mutations (for instance in the epithelial line, tumor suppressor PTEN gene) which can lead to an increased occurrence throughout the body. Signs and symptoms
Symptoms of AVM vary according to the location of the malformation. Roughly 88% of people with an AVM are asymptomatic; often the malformation is discovered as part of an autopsy or during treatment of an unrelated disorder (called in medicine an "incidental finding"); in rare cases, its expansion or a micro-bleed from an AVM in the brain can cause epilepsy, neurological deficit, or pain.The most general symptoms of a cerebral AVM include headaches and epileptic seizures, with more specific symptoms occurring that normally depend on the location of the malformation and the individual. Such possible symptoms include:
Difficulties with movement coordination, including muscle weakness and even paralysis;
Vertigo (dizziness);
Difficulties of speech (dysarthria) and communication, such as aphasia;
Difficulties with everyday activities, such as apraxia;
Abnormal sensations (numbness, tingling, or spontaneous pain);
Memory and thought-related problems, such as confusion, dementia or hallucinations.Cerebral AVMs may present themselves in a number of different ways:

Bleeding (45% of cases)
Acute onset of severe headache.
Carcinoid tumors, particularly those derived from the embryologic foregut (lungs, thymus), occur in isolated cases. Multiple subcutaneous and visceral lipomas, angiofibromas, and collagenomas may also occur. Genetic
People with multiple endocrine neoplasia type 1 are born with one mutated copy of the MEN1 gene in each cell. Then, during their lifetime, the other copy of the gene is mutated in a small number of cells. These genetic changes result in no functional copies of the MEN1 gene in selected cells, allowing the cells to divide with little control and form tumors. This is known as Knudsons two-hit hypothesis and is a common feature seen with inherited defects in tumor suppressor genes. Oncogenes can become neoplastic with only one activating mutation, but tumor suppressors inherited from both mother and father must be damaged before they lose their effectiveness. The exception to the "two-hit hypothesis" occurs when suppressor genes exhibit dose-response, such as ATR. The exact function of MEN1 and the protein, menin, produced by this gene is not known, but following the inheritance rules of the "two-hit hypothesis" indicates that it acts as a tumor suppressor. Diagnosis
In a diagnostic workup individuals with a combination of endocrine neoplasias suggestive of the MEN1 syndrome are recommended to have a mutational analysis of the MEN1 gene if additional diagnostic criteria are sufficiently met, mainly including:
age <40 years
positive family history
multifocal or recurrent neoplasia
two or more organ systems affected

Types
Multiple endocrine neoplasia or MEN is part of a group of disorders that affect the bodys network of hormone-producing glands (the endocrine system).