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Yao Syndrome

Yao syndrome (formerly called NOD2-associated autoinflammatory disease) is a periodic disease characterized by fever and abnormal inflammation affecting many parts of the body, particularly the skin (dermatitis), joints (polyarthritis/leg swelling), gastrointestinal system, and sicca-like symptoms associated with specific NOD2 sequence variants.

Inflammation is a normal immune system response to injury and foreign invaders (such as bacteria). In people with Yao syndrome, part of the immune system called the innate immune response is turned on (activated) abnormally, which causes fevers and inflammation-related damage to tissues and organs.

The episodes of fever and inflammation associated with Yao syndrome can last for several days and occur weeks to months apart. During these episodes, most affected individuals develop reddened, inflamed areas on the skin called erythematous patches or plaques. This reddening occurs most commonly on the face, chest, and back but can also affect the arms and legs. Episodes of joint pain and inflammation similar to arthritis are common, particularly in the legs, as is swelling of the ankles and feet. Inflammation also affects the gastrointestinal system, causing attacks of abdominal pain, bloating, and cramping with diarrhoea in more than half of affected individuals. Dry eyes and dry mouth (described as "sicca-like" symptoms, which refers to dryness) are reported in about half of people with this disease. Other potential signs and symptoms of Yao syndrome include mouth sores, chest pain, and enlargement of various glands.

Yao syndrome is usually diagnosed in adulthood. It is a long-lasting (chronic) disease, and episodes can recur for many years.

As a systemic disease, Yao syndrome uncommonly affects the solid internal organs, but it can be complicated with chronic pain syndrome and even disability.

Yao syndrome has an estimated prevalence of 1 in 10,000 to 1 in 100,000 people worldwide. Studies suggest that it is among the most common systemic (affecting the whole body) autoinflammatory diseases in adults. For unknown reasons, Yao syndrome appears to affect women more frequently than men.

Glucocorticoids or sulfasalazine may be considered as the first-line treatment option, and interleukin (IL)-1/IL-6 inhibitors may be tried for refractory (difficult/treatment resistant) cases.

References:

- Yao syndrome, Genetics Home Reference, NIH U.S. National Library of Medicine, https://ghr.nlm.nih.gov/condition/yao-syndrome

- Yao et al., Am J Med. 2017 Mar;130(3):365.e13-365.e18. doi: 10.1016/j.amjmed.2016.09.028. Epub 2016 Oct 28.

“A Systematic Analysis of Treatment and Outcomes of NOD2-Associated Autoinflammatory Disease.” https://www.ncbi.nlm.nih.gov/pubmed/27984003