Cyclic vomiting syndrome

Cyclic vomiting syndrome is a disorder that causes recurrent episodes of nausea, vomiting, and tiredness (lethargy). This condition is diagnosed most often in young children, but it can affect people of any age.

Cyclic vomiting syndrome is characterized by attacks of intense nausea, vomiting, and lethargy that last anywhere from an hour to 10 days. An affected person may vomit several times per hour, potentially leading to a dangerous loss of fluids (dehydration). Additional symptoms can include unusually pale skin (pallor), abdominal pain, diarrhea, headache, and an increased sensitivity to light (photophobia) or to sound (phonophobia). In most affected people, the signs and symptoms of each attack are quite similar. These attacks can be debilitating, making it difficult for an affected person to go to work or school.

Episodes of nausea and vomiting can be triggered by several different factors. The most common triggers are emotional excitement and infections. Other triggers can include periods without eating (fasting), temperature extremes, lack of sleep, overexertion, allergies, ingesting certain foods or alcohol, and menstruation.

If the condition is not treated, attacks typically occur four to 12 times per year. Between episodes, vomiting is absent, and nausea is either absent or much reduced. However, many affected people experience other symptoms during and between episodes, including pain, digestive disorders such as gastroesophageal reflux and irritable bowel syndrome, and fainting spells (syncope). People with cyclic vomiting syndrome are also more likely than people without the disorder to experience depression, anxiety, and panic disorder. It is unclear how these health conditions are related to nausea and vomiting.

Cyclic vomiting syndrome is generally considered to be a variant of migraines, which are severe headaches often associated with pain, nausea, vomiting, and extreme sensitivity to light and sound. Many people with cyclic vomiting syndrome have a family history of migraines, and attacks of nausea and vomiting may be replaced by migraine headaches as an affected person gets older.

Most people with cyclic vomiting syndrome have normal intelligence, although some affected people have experienced developmental delay or intellectual disability, muscle weakness (myopathy), and/or seizures. People with these additional features are said to have cyclic vomiting syndrome plus.

The exact prevalence of cyclic vomiting syndrome is unknown; estimates range from 4 to 2,000 per 100,000 children. The condition is diagnosed less commonly in adults, although recent studies suggest that the condition could be as common in adults as in children.

Although the exact causes of cyclic vomiting syndrome have yet to be determined, researchers have proposed several factors that may contribute to the disorder. These factors include changes in brain function, hormonal abnormalities, and gastrointestinal problems. Many researchers believe that cyclic vomiting syndrome is a migraine-like condition, which suggests that it is related to changes in signaling between nerve cells (neurons) in certain areas of the brain.

Some cases of cyclic vomiting syndrome may be related to genetic changes in mitochondrial DNA. Mitochondria are structures within cells that convert the energy from food into a form that cells can use. Although most DNA is packaged in chromosomes within the nucleus, mitochondria also have a small amount of their own DNA (known as mitochondrial DNA or mtDNA).

Several changes in mitochondrial DNA have been associated with cyclic vomiting syndrome. Some of these changes alter single DNA building blocks (nucleotides), whereas others rearrange larger segments of mitochondrial DNA. These changes likely impair the ability of mitochondria to produce energy. Defects in energy production may lead to symptoms during periods when the body requires more energy, such as when the immune system is fighting an infection. However, it remains unclear how changes in mitochondrial function are related to recurrent episodes of nausea and vomiting.

Read more about mitochondrial DNA.

In most cases of cyclic vomiting syndrome, affected people have no known history of the disorder in their family. However, many affected individuals have a family history of related conditions, such as migraines, in their mothers and other maternal relatives. This family history suggests an inheritance pattern known as maternal inheritance or mitochondrial inheritance, which applies to genes contained in mitochondrial DNA. Disorders with mitochondrial inheritance can appear in every generation of a family and can affect both males and females. However, because mitochondria can be passed from one generation to the next only through egg cells (not through sperm cells), only females pass mitochondrial conditions to their children.