Diagnosing DADA2 and Understanding Test Results

Confirming a diagnosis of DADA2 requires a careful evaluation by specialists. Because the symptoms can overlap with so many other conditions, doctors typically look at a combination of your clinical symptoms, a biochemical test of your enzyme levels, and a genetic map of your DNA ^[1][2].

How DADA2 is Diagnosed

There is no single universal rule for diagnosis, but specialists generally confirm DADA2 by combining evidence from the following areas:

1. Genetic Sequencing (Molecular Testing)

Genetic testing looks for variants (mutations) in the ADA2 gene ^[2]. Because DADA2 is recessive, diagnosing the condition typically involves finding biallelic variants—meaning one pathogenic (disease-causing) variant inherited from each parent ^[3].

• Understanding the Results: The lab report will detail specific changes in the DNA. If a variant is listed as “pathogenic” or “likely pathogenic,” it means it is known to cause disease.
• Variants of Uncertain Significance (VUS): Sometimes a variant is found, but there isn’t enough evidence to know if it causes disease or is just a harmless genetic difference. A VUS alone does not establish a diagnosis.
• The “Hidden” Variant: If your doctor finds only one variant but your clinical picture strongly points to DADA2, they may need to run specialized genetic tests (like deletion/duplication analysis) to find a second variant that standard sequencing might have missed ^[4][5].

2. The Enzyme Test (Biochemical Testing)

The ADA2 enzyme activity assay measures how well the ADA2 protein is working in your blood plasma ^[6].

• What it shows: Most people with DADA2 have markedly reduced or absent enzyme activity ^[1].
• Limitations: While this test is highly sensitive, assay performance varies depending on the laboratory and sample handling. A borderline or unexpected result needs expert interpretation rather than being used alone to definitively confirm or exclude the disease. When genetic and enzyme results disagree, your specialist will guide the next steps.

3. Clinical Evidence

Doctors look for signs of systemic inflammation (like fevers), skin involvement (like livedo racemosa), neurological events (like early-onset stroke), or specific blood/immune issues ^[7][8]. An asymptomatic sibling can also be diagnosed based on genetic and enzyme testing alone.

DADA2 vs. Polyarteritis Nodosa (PAN)

Before the discovery of DADA2 in 2014, many patients were diagnosed with Polyarteritis Nodosa (PAN), a similar type of blood vessel inflammation ^[8]. While they look alike, there are key differences, though they can overlap:

Note: Blood counts and organ involvement can overlap significantly. Molecular testing is necessary to distinguish the two when DADA2 is suspected.

Other Common Misdiagnoses

Because DADA2 can attack the bone marrow, it is sometimes mistaken for rare blood disorders:

• Pure Red Cell Aplasia (PRCA): A condition where the body stops making red blood cells ^[11].
• Diamond–Blackfan Anemia (DBA): A genetic anemia. If a patient is diagnosed with DBA but the standard genetic tests for it are negative, doctors should test for DADA2 ^[12].

Checklist: A Thorough Diagnostic Evaluation

If DADA2 is suspected or confirmed, an individualized evaluation should include components such as:

• [ ] Full Gene Sequencing: Specifically looking at the ADA2 gene, with deletion/duplication testing if needed ^[2].
• [ ] ADA2 Enzyme Activity Assay: To check if the protein is functional (when available) ^[6].
• [ ] Complete Blood Count (CBC): To check for low red cells, white cells, or platelets ^[13].
• [ ] Inflammatory Markers: Testing for high CRP or ESR ^[14].
• [ ] Immunoglobulins: To assess antibody levels (IgG, IgM, IgA) and vaccine responses ^[15].
• [ ] Organ Function: Repeated blood-pressure measurements, renal function and urinalysis, and liver tests.
• [ ] Imaging Considerations: A baseline brain MRI/MRA may be appropriate for many patients to check for “silent” strokes, but this is individualized. Your neurology team will decide based on symptoms, age, and prior imaging ^[16].