About one in three people with Sjögren’s syndrome also has another autoimmune disease. When Sjögren’s occurs alongside another condition, it’s historically been called “secondary” Sjögren’s, while cases that appear on their own are called “primary.” A large population study from Madrid found that 34.8% of all Sjögren’s cases were secondary, with rheumatoid arthritis and lupus accounting for the vast majority of those overlaps.
Rheumatoid Arthritis
Rheumatoid arthritis (RA) is the single most common autoimmune disease linked to Sjögren’s. In the Madrid study, RA accounted for 20.3% of all Sjögren’s cases. And the overlap runs in the other direction too: data from the Corrona registry, which tracked over 24,000 RA patients in the United States, found that roughly 30% of people with RA also had a Sjögren’s diagnosis.
When the two conditions coexist, the disease burden tends to be higher than with RA alone. People with both conditions are more likely to be female, older at diagnosis, and to have had RA for longer. They also show higher disease activity scores, more joint erosion, and nearly twice the rate of subcutaneous nodules (hard lumps under the skin near joints). Beyond the joints, having both conditions is associated with more morning stiffness, greater self-reported pain, and higher rates of hypertension, cardiovascular disease, and serious infections requiring hospitalization.
In practical terms, if you have RA and begin noticing persistent dry eyes, dry mouth, or difficulty swallowing, these symptoms are worth raising with your rheumatologist rather than dismissing as side effects of medication.
Systemic Lupus Erythematosus (Lupus)
Lupus is the second most common autoimmune disease associated with Sjögren’s, representing about 8.5% of all Sjögren’s cases in population data. Looking from the lupus side, systematic reviews estimate that 14% to 18% of people with lupus also meet the criteria for secondary Sjögren’s, though some individual studies have reported rates as high as 33%.
The two conditions share several features that can make them hard to distinguish. Both involve antibodies to Ro (SSA) proteins, both can cause joint pain and fatigue, and both disproportionately affect women. Predictive factors for developing Sjögren’s in someone who already has lupus include measurable gland dysfunction, a specific pattern of immune cell infiltration in salivary gland tissue, and the presence of anti-Ro antibodies. If you have lupus and develop worsening dryness in your eyes or mouth that doesn’t match your current treatment picture, it may signal overlapping Sjögren’s rather than a lupus flare.
Scleroderma (Systemic Sclerosis)
Scleroderma, a condition characterized by thickening and hardening of the skin and connective tissue, overlaps with Sjögren’s more often than many people realize. In one cohort study of 128 scleroderma patients, 20% met the criteria for secondary Sjögren’s. This overlap appears especially common in patients who carry a particular antibody called anticentromere antibody (ACA). People with this overlap pattern tend to have milder organ involvement from scleroderma itself, but they carry a higher risk of developing lymphoma, a type of blood cancer that is already a known complication of Sjögren’s on its own.
Autoimmune Thyroid Disease
Hashimoto’s thyroiditis, the most common cause of an underactive thyroid, shows up in people with primary Sjögren’s at roughly three to six times the rate seen in the general population. One analysis found a 6.26% prevalence of Hashimoto’s among primary Sjögren’s patients, compared to 1% to 2% in the general population. Because thyroid symptoms like fatigue, brain fog, and muscle aches overlap heavily with Sjögren’s symptoms, the thyroid component can easily go undiagnosed. A simple blood test for thyroid function can catch it.
Primary Biliary Cholangitis
Primary biliary cholangitis (PBC) is a chronic liver disease in which the immune system gradually destroys the small bile ducts inside the liver. Observational studies have consistently found that Sjögren’s occurs at a higher rate in people with PBC than in the general population. The connection makes biological sense: both conditions involve immune-driven destruction of epithelial cells (the cells lining ducts and glands). If you have Sjögren’s and develop unexplained itching, fatigue that worsens beyond your baseline, or abnormal liver function on routine blood work, PBC is one possibility worth investigating.
Why These Conditions Cluster Together
The overlap between Sjögren’s and other autoimmune diseases isn’t coincidental. Gene expression studies comparing Sjögren’s, rheumatoid arthritis, and lupus have identified a shared molecular signature across all three. The most prominent feature is overactivation of a group of genes related to type I interferon signaling, a branch of the immune system that normally helps fight viruses. In these conditions, the interferon pathway stays switched on when it shouldn’t be, driving chronic inflammation.
Beyond interferon, researchers have found shared overexpression of genes involved in inflammatory cytokine signaling (the chemical messengers that amplify immune responses), abnormal cell death pathways, and immune activation through Toll-like receptors, which are proteins that normally detect infections. This common molecular machinery helps explain why having one autoimmune disease raises the risk for others. Your immune system isn’t malfunctioning in one isolated way; it’s running a broader program of dysregulation that can target multiple organs and tissues.
Multiple Sclerosis
The relationship between Sjögren’s and multiple sclerosis (MS) is more complicated than the other associations. Both are immune-mediated conditions, and they share some immunological features and genetic predispositions. However, a genetic analysis using a technique called Mendelian randomization found something unexpected: MS may actually have a protective effect against developing primary Sjögren’s, with the data suggesting roughly a 10% decrease in risk. The reverse direction, whether Sjögren’s influences MS risk, did not reach statistical significance. So while the two conditions can coexist in the same person, the relationship appears fundamentally different from the clustering seen with RA, lupus, and scleroderma.
How Overlap Is Diagnosed
The current standard for classifying Sjögren’s is the 2016 ACR/EULAR criteria, which use a scoring system based on five objective measures: the presence of anti-SSA/Ro antibodies, a specific pattern of immune cell clusters found on a biopsy of a minor salivary gland (taken from the inside of the lower lip), an eye surface staining score that measures damage from dryness, a Schirmer’s test that measures tear production, and an unstimulated salivary flow rate. A score of 4 or higher confirms the classification. The antibody test and the salivary gland biopsy carry the most weight, at 3 points each.
If you already have a diagnosed autoimmune condition and develop new or worsening dryness of the eyes or mouth, persistent fatigue that your current treatment doesn’t explain, or swelling of the salivary glands, these are the kinds of symptoms that typically prompt evaluation for overlapping Sjögren’s. The testing process is the same regardless of whether Sjögren’s turns out to be primary or secondary.