McLeod syndrome or McLeod neuroacanthocytosis syndrome is extremely rare, with only about 150 reported cases worldwide. The condition develops mostly in boys and men and affects many parts of the body, including the red blood cells. When the blood cell abnormalities were first discovered, researchers believed they were of no significance other than blood-product phenotyping. Newer studies show, however, that over time people with McLeod syndrome may develop significant neurological, hematological, and muscular problems.
McLeod syndrome affects the brain and spinal cord, causing significant motor issues. Individuals with the condition may experience involuntary movements such as jerking of the arms and legs, muscle tensing in the face and throat leading to vocal tics and grimacing, and dystonia of the tongue that makes swallowing difficult. Muscle weakness and atrophy can also occur, possibly due to nerve degeneration, leading to arrhythmias and an enlarged heart.
Half of the people with McLeod syndrome experience seizures and may have problems learning and processing new information. Behavioral changes such as impulsiveness can occur, and some develop psychiatric conditions like bipolar disorder, depression, OCD, and psychosis. While the movement issues and learning difficulties associated with McLeod's syndrome tend to worsen over time, behavioral changes are usually not progressive.
The symptoms of McLeod's syndrome usually present in mid-adulthood, most commonly in middle-aged men. That said, neurological symptoms can develop at any age between 25 and 60. Behavioral issues such as lack of restraint, personality changes, and an inability to care for oneself are often the first signs that something is wrong.
Mutations of the XK gene cause McLeod syndrome. This gene is responsible for producing the XK protein found throughout the body, which carries the Kx blood antigen. The mutation causes the XK protein to be too short, ineffective, or completely absent, preventing the formation of the Kx blood antigen. Despite understanding this disease process, experts do not know how it causes the symptoms of McLeod's syndrome.
The XK gene is located on the X chromosome, making McLeod syndrome is an X-linked recessive condition. As such, males are more affected by the mutation than females. For a female to develop McLeod syndrome, both of her X chromosomes must carry the mutation. Since men have only one X chromosome, they are more likely to develop the disorder.
It can be difficult to diagnose McLeod syndrome because it is so rare. Doctors consider the onset of symptoms and the patient's medical history, do a physical examination, and take blood tests to determine the diagnosis. Blood tests show weakened antigens and may display spiky cell membranes or acanthocytosis under a microscope. Some people experience severe reactions after blood transfusions, and newborn males with the mutation may present with severe anemia.
Other tests may return abnormal results, too, highlighting the systemic effects of the condition. The liver enzymes LDH, AST, and ALT may be elevated. While this would normally indicate problems with the liver, in McLeod syndrome, it can point to problems in the muscle cells. PET scans may show reduced glucose uptake in the brain, and muscle biopsies may indicate atrophy or significant variability in fiber size. The myelin coating of nerve fibers may sustain damage, and brain atrophy may occur in some areas.
Currently, there is no cure for McLeod syndrome, and treatment centers on symptoms and supportive care. Dopamine blockers have been successful at decreasing the severity of involuntary movements, while anticonvulsives can treat seizures, and antidepressants may ease mood changes. Botox injections can improve dystonia, but some people require a feeding tube if muscle spasms impact the ability to swallow food safely. Many medical professionals prescribe physical, occupational, and speech therapy, as well.
In most affected males, McLeod syndrome symptoms peak at around age 50. Some people experience mild symptoms, having only hematological findings without any muscular or neurological issues. Such a diagnosis usually results in a normal lifespan. However, people with severe symptoms have a prognosis of five to 10 years after diagnosis. This is especially true if they experience cardiomyopathy, which increases the risk of sudden cardiac death from congestive heart failure.
Since McLeod syndrome is an X-linked genetic disease, a diagnosis has implications for blood relatives. Males with the disorder can not pass it on to their sons — X chromosomes are only inherited from the mother — but their daughters will be carriers. With each pregnancy, female carriers have a 25% chance of having a daughter who is a carrier, a daughter who is not a carrier, a son with the disease, and a son who is unaffected.
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