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Blau syndrome
This condition typically manifests in early childhood, causing symptoms such as arthritis, rashes, and uveitis. It is caused by genetic changes in the NOD2 gene and follows an autosomal dominant inheritance pattern.
Overview
Blau syndrome is a rare genetic condition that falls under the category of autoinflammatory diseases. These diseases occur when the body's immune system mistakenly attacks its own tissues, leading to recurrent or chronic inflammation [PMID:33671569]. In Blau syndrome, the main areas affected are commonly the joints, skin, and eyes, with symptoms often beginning before the age of five years. The condition is progressive, meaning symptoms can worsen over time.
The syndrome was first described by two independent researchers, Dr. Edward Blau and Dr. Douglas Jabs, hence its name. It is important to distinguish Blau syndrome from early-onset sarcoidosis, as they share similar clinical features and are both linked to variants in the NOD2 gene [PMID:24076352]. However, Blau syndrome specifically refers to the inherited form with a clear genetic cause.
Symptoms & clinical features
The primary clinical features of Blau syndrome include polyarthritis (inflammation of multiple joints), dermatitis (skin rash), and uveitis (inflammation inside the eye). Joint involvement is typically symmetrical, affecting the small joints of the hands and feet, wrists, ankles, and knees. This can lead to joint swelling, pain, and stiffness, and over time may result in limited movement and joint damage.
The skin rash associated with Blau syndrome is often described as an erythematous (reddened) papular rash, meaning small, raised bumps [PMID:33671569]. It can appear on various parts of the body and may fluctuate in severity. Eye inflammation, specifically uveitis, can affect different parts of the eye and, if left untreated, may lead to serious complications including cataracts, glaucoma, and vision impairment or loss.
While joints, skin, and eyes are most commonly affected, some individuals with Blau syndrome may experience inflammation in other organs, such as the liver, spleen, or kidneys. Other symptoms can include fever, lymphadenopathy (swollen lymph nodes), and gastrointestinal issues.
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Affected organs
The organs most commonly affected in Blau syndrome are the joints, skin, and eyes. Within the joints, the synovium (lining of the joint capsule) becomes inflamed, leading to the characteristic arthritis.
On the skin, the inflammation manifests as a rash. In the eyes, the uvea (the middle layer of the eye) is primarily affected, which can have significant consequences for vision.
Risks & severity
Blau syndrome has a variable spectrum of severity; some individuals experience milder symptoms, while others have more severe and widespread inflammation. The condition typically begins in early childhood, most often before the age of five [PMID:24076352]. The chronic nature of the inflammation means that ongoing management is generally required to control symptoms and prevent organ damage. Complications can arise from persistent inflammation, particularly in the eyes, where untreated uveitis can lead to irreversible vision loss. Joint involvement can also lead to long-term mobility issues and joint destruction if not managed appropriately. As a rare condition, the exact prevalence is not well established.
Genetic causes
Blau syndrome is caused by pathogenic variants in the NOD2 gene, also known as CARD15. This gene provides instructions for making a protein involved in the immune system, specifically playing a role in the innate immune response and sensing bacterial components [PMID:24076352]. The NOD2 protein is found predominantly in immune cells and intestinal cells.
Pathogenic changes in NOD2 in Blau syndrome lead to an overactive immune response. Instead of properly regulating inflammation, the altered NOD2 protein triggers inappropriate inflammatory reactions, leading to the chronic symptoms seen in the condition [PMID:33671569]. These variants are typically gain-of-function, meaning the protein becomes hyperactive.
- NOD2 nucleotide binding oligomerization domain containing 2
Inheritance pattern
Blau syndrome follows an autosomal dominant inheritance pattern. This means that a person only needs to inherit one copy of the altered NOD2 gene from one parent to develop the condition. If a parent has Blau syndrome, there is a 50% chance with each pregnancy that their child will inherit the pathogenic variant and therefore also develop the condition.
In some cases, Blau syndrome can arise from a de novo (new) pathogenic variant in the NOD2 gene, meaning the genetic change occurred for the first time in the affected individual and was not inherited from either parent. In such situations, the parents do not carry the pathogenic variant, but the affected individual can still pass it on to their children.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
Diagnosis & testing
Diagnosing Blau syndrome typically involves a combination of clinical evaluation and genetic testing. A paediatrician or a rheumatologist may suspect the condition based on the presence of the characteristic triad of arthritis, dermatitis, and uveitis, especially when symptoms begin in early childhood.
Genetic testing for pathogenic variants in the NOD2 gene is essential to confirm a diagnosis. This testing can be accessed through the NHS Genomic Medicine Service (GMS) via an appropriate clinical referral, usually from a clinical geneticist or specialist clinician. Relevant NHS R-codes would be used for this genetic testing, which aims to identify the specific genetic change responsible for the condition. Family history can also be a significant indicator, given the autosomal dominant inheritance pattern.
Management & lifestyle
Managing Blau syndrome focuses on controlling inflammation, alleviating symptoms, and preventing long-term organ damage. Treatment approaches are highly individualised and are typically overseen by a multidisciplinary team of specialists, which may include rheumatologists, ophthalmologists, and dermatologists.
Medications to suppress the immune system and reduce inflammation are a cornerstone of treatment. These may include corticosteroids, conventional disease-modifying anti-rheumatic drugs (DMARDs), and increasingly, biologic therapies that target specific inflammatory pathways. Regular monitoring of joint, skin, and eye health is crucial to adjust treatment as needed and address potential complications promptly. Genetic counsellors can provide valuable support and information regarding the genetic aspects of the condition and its implications for family planning.
UK care pathway
In the UK, individuals suspected of having genetic conditions like Blau syndrome would typically be referred by their GP or specialist to a clinical genetics service. These services are part of the NHS Genomic Medicine Service (GMS) and are responsible for confirming diagnoses through genetic testing, utilising specific R-codes from the GMS test directory. Genetic counsellors within these services play a vital role, offering information, support, and guidance on inherited conditions and their implications for families. The care pathway emphasises a holistic approach, integrating genetic counselling with specialist medical management.
Frequently asked questions
Is Blau syndrome contagious?
No, Blau syndrome is not contagious. It is a genetic condition caused by changes in the NOD2 gene and cannot be passed from person to person through contact.
What is the typical age for symptoms to start?
Symptoms of Blau syndrome usually begin in early childhood, most commonly before a child reaches five years of age. However, the exact age of onset can vary between individuals.
Can Blau syndrome affect my vision?
Yes, chronic eye inflammation (uveitis) is a common feature of Blau syndrome. If not managed effectively, it can lead to complications such as cataracts, glaucoma, and can potentially impair vision.
Is there a cure for Blau syndrome?
Currently, there is no cure for Blau syndrome. However, treatments are available to manage symptoms, control inflammation, and help prevent long-term damage to affected organs like joints and eyes.
If I have Blau syndrome, what is the chance my children will inherit it?
Blau syndrome is an autosomal dominant condition. If you have the condition, each of your children has a 50% chance of inheriting the altered gene and therefore developing Blau syndrome, with each pregnancy.
References
- Wang OJE, Jacob M, Crawford RI. Blau Syndrome (Juvenile Systemic Granulomatosis): State-Of-The-Art Review. Pediatric dermatology. 2025. PMID: 40456554
- Smith JR, Mochizuki M. Sarcoid Uveitis in Children. Ocular immunology and inflammation. 2023. PMID: 37983819
- Rose CD, Martin TM, Wouters CH. Blau syndrome revisited. Current opinion in rheumatology. 2011. PMID: 21788900
- Lachmann HJ. Periodic fever syndromes. Best practice & research. Clinical rheumatology. 2017. PMID: 29773275
- Alghamdi M. Autoinflammatory Disease-Associated Vasculitis/Vasculopathy. Current rheumatology reports. 2018. PMID: 30446874
- Galeazzi M, Gasbarrini G, Ghirardello A. Autoinflammatory syndromes. Clinical and experimental rheumatology. 2006. PMID: 16466630
- Suresh S, Tsui E. Ocular manifestations of Blau syndrome. Current opinion in ophthalmology. 2020. PMID: 33009086
- Federici S, Caorsi R, Gattorno M. The autoinflammatory diseases. Swiss medical weekly. 2012. PMID: 22714396