Patients whose vasculitis is limited to their kidneys appear to be at a greater risk of having an accompanying autoimmune disease, researchers also found.
The study, “Prevalence of overlap of antineutrophil cytoplasmic antibody associated vasculitis with systemic autoimmune diseases: an unrecognized example of poliautoimmunity,” was published in the journal Clinical Rheumatology.
ANCA-associated vasculitis (AAV) is a group of rare autoimmune diseases characterized by inflammation of small blood vessels.
Overlap syndrome — occurring when a patient has two or more systemic autoimmune diseases — is commonly observed in patients with rheumatic diseases.
However, the coexistence of AAV with another systemic autoimmune disease has rarely been documented, likely due to a lack of published literature on this disease.
Additionally, since these conditions are rare, there is a lack of large-scale epidemiological and clinical studies, despite being a significant cause of complications and death.
Researchers in this study set out to estimate the frequency of overlap of AAV with other systemic autoimmune diseases through a single-center, retrospective study carried out over an observation period of 15 years. Researchers also thoroughly assessed the clinical characteristics of patients with overlap syndrome.
Among the 247 patients examined, 28, or 11.3%, had another autoimmune disease. The most common AAV subtype was renal-limited vasculitis — when the disease only affects the blood vessels of the kidney — seen in 39% of patients with overlapping autoimmune diseases.
The remaining patients had granulomatosis with polyangiitis (29%), microscopic polyangiitis (25%), or eosinophilic granulomatosis with polyangiitis (7%).
The mean age at AAV diagnosis for these patients was 50, and 24 patients were positive for ANCA antibodies — autoantibodies that cause immune cells, called neutrophils, to attack blood vessels.
The main disease manifestations among those with overlapping diseases were seen in the kidneys (79%), followed by the ear, nose and throat (43%), and pulmonary and peripheral neuropathy, or nerve pain (32%).
Among the autoimmune diseases in this patient population, the most common was rheumatoid arthritis, which was present in 39% of patients.
Additionally, 14% of patients had Sjögren’s syndrome and systemic sclerosis, 11% had mixed connective tissue disease, 7% had systemic lupus erythematosus and juvenile idiopathic arthritis, and 4% had ankylosing spondylitis, a type of arthritis that affects the spine.
In 32% of patients, a diagnosis of AAV was made simultaneously with the other autoimmune disease. For the remaining patients, the median time between the autoimmune disease and AAV diagnosis was 173 months.
“The prevalence of overlap AAV with other autoimmune diseases was low. The most common AAV phenotype was renal-limited vasculitis, and the most frequent overlap disease was rheumatoid arthritis,” the researchers concluded.