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PubMed This is a summary of 7 peer-reviewed journal articles Updated
Rheumatology

Symptoms & Mimics: Daily Manifestations and Distinguishing from Behçet's disease

At a Glance

A20 haploinsufficiency can cause childhood-onset fevers, mouth or genital ulcers, bowel symptoms, joint pain, and rashes. Early onset, family history, recurrent fever, and gastrointestinal symptoms may prompt genetic evaluation, but no single feature separates it from Behçet’s disease.

A20 Haploinsufficiency (HA20) shares clinical overlap with several other better-known conditions. Because it is rare, many patients are initially diagnosed with more common diseases before genetic testing and clinical context reveal the true cause [1].

Daily Manifestations and Clinical Overlap

For many individuals, HA20 begins early in childhood (median age of onset around 3.3 years in a large cohort), though presentation in adolescence or adulthood occurs [2]. The disease can produce relapsing inflammation (flares) or persistent symptoms [2]. Frequencies vary with age, ascertainment, and cohort size, but commonly reported features include:

  • Recurrent Fevers: A majority of patients in cohorts experience fevers that occur as part of the disease’s inflammatory cycle [2].
  • Mucocutaneous ulcers: Painful sores in the mouth (oral ulcers) occur frequently [3]. Genital ulcers can also occur in a subset of patients over time [3].
  • Gastrointestinal (GI) Issues: Abdominal pain, diarrhea, or inflammation in the gut are widely reported [2]. In some cases, the inflammation in the gut can resemble colitis or intestinal ulcers [3].
  • Joint and Skin Problems: Many patients experience arthritis (swollen, painful joints) or arthralgia (joint pain without swelling) [2]. Skin rashes, including red lumps on the legs (erythema nodosum), are also seen [3].

Distinguishing HA20 from Behçet’s Disease

For many years, patients with these symptoms were broadly diagnosed with Behçet’s disease (BD). While HA20 and BD share symptoms like mouth sores and joint pain, there are clinical clues that may prompt a doctor to consider genetic testing for HA20. These are clues, not absolute diagnostic rules—no single feature perfectly distinguishes HA20 from BD. Pediatric Behçet’s does exist, familial clustering can occur, and gastrointestinal and ocular findings overlap [4][5].

Clinical Clues Suspecting HA20 Classical Behçet’s Disease
Age of Onset Often very early childhood (e.g., median 3.3 years in cohorts) [2]. Usually young adulthood, though pediatric cases exist [4].
Family History Often familial [4]. Often sporadic, though familial cases occur [5].
Fevers Recurrent fever attacks are a hallmark feature [4]. Recurrent fever is less common [5].
GI Involvement Widely reported [2]. Less common overall [4].
Eye Involvement Uveitis occurs but is relatively infrequent [3]. Common; a major defining feature [4].

Note: Clinical criteria for Behçet disease and IBD are not replaced by genetic testing. A patient may still need evaluation for those conditions or for infection when symptoms warrant it.

Other Overlapping Conditions

Because HA20 is an autoinflammatory disease that can also have autoimmune features, it is frequently mistaken for other conditions:

  • Juvenile Idiopathic Arthritis (JIA) or Rheumatoid Arthritis (RA): If joint swelling is prominent, a patient might be diagnosed with JIA or RA before other systemic symptoms are recognized [1].
  • Systemic Lupus Erythematosus (SLE): Some individuals develop symptoms and laboratory findings that overlap with lupus, including positive ANA (Antinuclear Antibodies) tests [6][1]. However, ANA is a non-specific marker that can be positive in many conditions or even in healthy people; laboratory findings should never be interpreted in isolation without careful clinical evaluation.
  • Inflammatory Bowel Disease (IBD): When GI symptoms are severe, patients may be misdiagnosed with Crohn’s disease or ulcerative colitis [7].

The Rule of “Same Mutation, Different Symptoms”

One of the most complex aspects of HA20 is phenotypic variability. Even within the same family, two people with the exact same genetic variant can have very different symptoms [1]. One person might have severe fevers and gut issues, while their relative may have only occasional mouth sores [7]. This is why doctors look at the whole family history—mild symptoms in one relative can be a major clue for another’s diagnosis [4].

Common questions in this guide

What symptoms are common with A20 haploinsufficiency?
Common features include recurrent fevers, painful mouth ulcers, and sometimes genital ulcers. People may also have abdominal pain, diarrhea or bowel inflammation, joint swelling or pain, and skin rashes such as erythema nodosum. Symptoms may come in flares or persist.
How can doctors tell HA20 apart from Behçet’s disease?
A20 haploinsufficiency and Behçet’s disease can both cause mouth ulcers and joint symptoms. Very early childhood onset, recurrent fever, gastrointestinal involvement, or similar symptoms in relatives may raise suspicion for HA20, while eye inflammation is more common in classical Behçet’s disease. These are clues rather than rules, so no single feature makes the diagnosis.
Can HA20 cause colitis or other bowel problems?
Yes. HA20 may cause abdominal pain, diarrhea, gut inflammation, or intestinal ulcers that can resemble colitis, Crohn’s disease, or ulcerative colitis. Because infection and inflammatory bowel disease can have similar symptoms, a clinician may recommend additional evaluation rather than assuming the cause.
Can HA20 be mistaken for arthritis, lupus, or inflammatory bowel disease?
Yes. Joint swelling or pain may initially look like juvenile idiopathic arthritis or rheumatoid arthritis, and bowel symptoms may resemble Crohn’s disease or ulcerative colitis. Some people also have findings such as a positive ANA test, but that result is not specific and must be interpreted with symptoms, examination, and other tests.
Should someone with HA20 symptoms have an eye exam?
Uveitis can occur in HA20, although it is reported less often than in classical Behçet’s disease. Ask the treating clinician whether an eye examination is appropriate, especially if there are eye symptoms or a concern about inflammation.
Can relatives with the same HA20 variant have different symptoms?
Yes. A20 haploinsufficiency has substantial variation, so one relative may have severe fevers and bowel problems while another has only occasional mouth ulcers. Reviewing mild or previously unexplained symptoms in relatives can help clinicians recognize the condition.

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References

References (7)
  1. 1

    Haploinsufficiency of A20 (HA20): updates on the genetics, phenotype, pathogenesis and treatment.

    Yu MP, Xu XS, Zhou Q, et al.

    World journal of pediatrics : WJP 2020; (16(6)):575-584 doi:10.1007/s12519-019-00288-6.

    PMID: 31587140
  2. 2

    Multicenter international cohort study of haploinsufficiency of A20 reveals novel genetic architecture and phenotypic evolution.

    He T, Wang J, Carpio Tumba M, et al.

    The Journal of allergy and clinical immunology 2026; (157(6)):1395-1410 doi:10.1016/j.jaci.2026.02.002.

    PMID: 41692116
  3. 3

    Tackling the diagnosis of HA20 in children: challenges of a highly variable clinical and genetic spectrum.

    Anselmi F, Frémond ML, Remaux H, et al.

    RMD open 2026; (12(1)) doi:10.1136/rmdopen-2025-006379.

    PMID: 41741169
  4. 4

    Haploinsufficiency of A20 caused by a novel nonsense variant or entire deletion of TNFAIP3 is clinically distinct from Behçet's disease.

    Tsuchida N, Kirino Y, Soejima Y, et al.

    Arthritis research & therapy 2019; (21(1)):137 doi:10.1186/s13075-019-1928-5.

    PMID: 31164164
  5. 5

    Autosomic dominant familial Behçet disease and haploinsufficiency A20: A review of the literature.

    Berteau F, Rouviere B, Delluc A, et al.

    Autoimmunity reviews 2018; (17(8)):809-815 doi:10.1016/j.autrev.2018.02.012.

    PMID: 29890348
  6. 6

    A20 haploinsufficiency diagnosis beyond systemic lupus erythematosus: A systematic review of the literature.

    Philip R, Elhani I, Gallou S, et al.

    Autoimmunity reviews 2025; (24(2)):103722 doi:10.1016/j.autrev.2024.103722.

    PMID: 39672252
  7. 7

    Expanding the spectrum of A20 haploinsufficiency in two Chinese families: cases report.

    Li GM, Liu HM, Guan WZ, et al.

    BMC medical genetics 2019; (20(1)):124 doi:10.1186/s12881-019-0856-1.

    PMID: 31299923

This page is for informational purposes only and does not constitute medical advice. A clinician should interpret symptoms and decide whether genetic, gastrointestinal, eye, or other evaluations are needed.

Guide contents A20 haploinsufficiency
Research & Literature
02 Biology & Diagnosis 04 Standard of Care Treatment