IBD diagnosis often comes before AAV, study finds

Researchers say more study needed to identify causal link

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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Inflammatory bowel disease (IBD) — a chronic disease where the bowel becomes inflamed, causing recurring lower abdominal pain and diarrhea — can overlap with ANCA-associated vasculitis (AAV) and is often diagnosed first, a study found.

The finding suggests a possible link between the two diseases, and that having IBD may increase the risk of developing AAV, a group of diseases marked by the production of self-reactive antibodies that trigger inflammation in small blood vessels and damage to multiple organs in the body.

However, “more research is needed to identify any causal association,” the scientists wrote.

The study, “Investigating the concomitance of anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitides and inflammatory bowel disease (IBD),” was published in Seminars in Arthritis and Rheumatism.

IBD is marked by chronic inflammation in the gastrointestinal tract that leads to intense cramps and loose, bloody stool. It includes Crohn’s disease, which typically develops in the small bowel, and ulcerative colitis, which causes ulcers, or open sores, in the large bowel. Abnormal immune responses are thought to contribute to IBD.

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IBD diagnosis often comes earlier than blood vessel inflammation

Earlier studies have suggested that Crohn’s disease and ulcerative colitis may occur along with AAV more frequently than would be expected by chance, perhaps due to common underlying inflammatory and immune mechanisms.

And “prior reported cases have noted the diagnosis of IBD preceding … [blood vessel inflammation] by years,” the researchers wrote.

The researchers, from Mayo Clinic College of Medicine and Science in Jacksonville, Florida, reviewed past records of 39 patients, most of them female, with both IBD and AAV from January 2020 to August 2023. Most were diagnosed with IBD before AAV. The median time between the two diagnoses was five years, ranging from less than a month to 38 years.

Regarding AAV types, 20 patients had granulomatosis with polyangiitis (GPA), six had microscopic polyangiitis (MPA), and four, eosinophilic granulomatosis with polyangiitis (EGPA). The type of AAV was unspecified in eight patients, and in one, the disease was limited to the kidneys.

Of the 20 GPA patients, 13 had ulcerative colitis and six had Crohn’s disease. One patient had unspecified IBD. The patients most commonly experienced neurological symptoms (35%), followed by skin symptoms, cough, and a deformity known as saddle nose (25% each).

Four of the MPA patients had ulcerative colitis, and the other two had Crohn’s disease. Two-thirds (66.7%) experienced kidney symptoms, with one patient requiring a transplant. Other symptoms included neurological manifestations, skin problems, shortness of breath, and interstitial lung disease, which causes the lung tissue to scar (16.7% each).

The four EGPA patients, evenly split between ulcerative colitis and Crohn’s disease, most frequently experienced kidney symptoms (75%), followed by neurological manifestations, shortness of breath, cough, and asthma (50% each).

“Our data identifies a substantially higher number of patients with [ulcerative colitis] than with Crohn’s,” the researchers wrote.

Remission, meaning showing no symptoms of AAV for a time, was achieved more frequently among patients who had ulcerative colitis versus those with  Crohn’s disease (80% vs. 61.5%), in line with “existing literature which notes remission in Crohn’s disease is less common,” the researchers wrote.

When the researchers looked at a group of 92 IBD patients who were tested for ANCAs during the same time period, the self-reactive antibodies that drive AAV in most cases, they found that 59 were positive for such antibodies.

Among those with ANCAs, one-third (33.3%) of ulcerative colitis patients and more than half (52.1%) of those with Crohn’s disease went on to develop AAV, suggesting “laboratory abnormalities of ANCA testing in IBD patients,” the researchers wrote.

These abnormalities “highlight a concern that a [disease-causing] mechanism may be present that has not yet been identified along with the associated triggers,” the researchers added.

The number of patients who have both IBD and AAV appears to be small, but “IBD may be underdiagnosed … as use of immunosuppressants including corticosteroids can suppress unimpeded [whole-body] inflammation and prevent … manifestation of bowel disease,” the team wrote.

“Further studies are required to ascertain a possible connectivity between the two disease processes and if any predisposition can be identified,” they concluded.