MTHFR Gene

Anencephaly is a condition that prevents the normal development of the brain and the bones of the skull. This condition results when a structure called the neural tube fails to close during the first few weeks of embryonic development. The neural tube is a layer of cells that ultimately develops into the brain and spinal cord. Because anencephaly is caused by abnormalities of the neural tube, it is classified as a neural tube defect.

Because the neural tube fails to close properly, the developing brain and spinal cord are exposed to the amniotic fluid that surrounds the fetus in the womb. This exposure causes the nervous system tissue to break down (degenerate). As a result, people with anencephaly are missing large parts of the brain called the cerebrum and cerebellum. These brain regions are necessary for thinking, hearing, vision, emotion, and coordinating movement. The bones of the skull are also missing or incompletely formed.

Because these nervous system abnormalities are so severe, almost all babies with anencephaly die before birth or within a few hours or days after birth.

Homocystinuria is an inherited disorder in which the body is unable to process certain building blocks of proteins (amino acids) properly. There are multiple forms of homocystinuria, which are distinguished by their signs and symptoms and genetic cause. The most common form of homocystinuria is characterized by nearsightedness (myopia), dislocation of the lens at the front of the eye, an increased risk of abnormal blood clotting, and brittle bones that are prone to fracture (osteoporosis) or other skeletal abnormalities. Some affected individuals also have developmental delay and learning problems.

Less common forms of homocystinuria can cause intellectual disability, failure to grow and gain weight at the expected rate (failure to thrive), seizures, problems with movement, and a blood disorder called megaloblastic anemia. Megaloblastic anemia occurs when a person has a low number of red blood cells (anemia), and the remaining red blood cells are larger than normal (megaloblastic).

The signs and symptoms of homocystinuria typically develop within the first year of life, although some mildly affected people may not develop features until later in childhood or adulthood.

Schizophrenia is a brain disorder classified as a psychosis, which means that it affects a person's thinking, sense of self, and perceptions. The disorder typically becomes evident during late adolescence or early adulthood.

Signs and symptoms of schizophrenia include false perceptions called hallucinations. Auditory hallucinations of voices are the most common hallucinations in schizophrenia, but affected individuals can also experience hallucinations of visions, smells, or touch (tactile) sensations. Strongly held false beliefs (delusions) are also characteristic of schizophrenia. For example, affected individuals may be certain that they are a particular historical figure or that they are being plotted against or controlled by others.

People with schizophrenia often have decreased ability to function at school, at work, and in social settings. Disordered thinking and concentration, inappropriate emotional responses, erratic speech and behavior, and difficulty with personal hygiene and everyday tasks can also occur. People with schizophrenia may have diminished facial expression and animation (flat affect), and in some cases become unresponsive (catatonic). Substance abuse and suicidal thoughts and actions are common in people with schizophrenia.

Certain movement problems such as tremors, facial tics, rigidity, and unusually slow movement (bradykinesia) or an inability to move (akinesia) are common in people with schizophrenia. In most cases these are side effects of medicines prescribed to help control the disorder. However, some affected individuals exhibit movement abnormalities before beginning treatment with medication.

Some people with schizophrenia have mild impairment of intellectual function, but schizophrenia is not associated with the same types of physical changes in the brain that occur in people with dementias such as Alzheimer disease.

Psychotic disorders such as schizophrenia are different from mood disorders, including depression and bipolar disorder, which primarily affect emotions. However, these disorders often occur together. Individuals who exhibit strong features of both schizophrenia and mood disorders are often given the diagnosis of schizoaffective disorder.