Bacterial Infections, Especially in Lungs, Common in AAV Patients in Southern China, Study Reports

Infection is a common complication of ANCA-associated vasculitis (AAV) that tends to develop within six months of diagnosis, and in cases of  “mixed” infections — those caused by more than one type of bacteria, or by bacteria and fungi — can take a major toll on survival, a study of patients in Southern China reports.

Lung bacterial infections were most commonly identified by researchers, mainly seen in people with active disease. Smoking, kidney problems, a need for dialysis, and low white blood cell (lymphocyte) counts were all linked with a higher infection risk.

The study, “Infectious profile in inpatients with ANCA-associated vasculitis: a single-center retrospective study from Southern China,” was published in the journal Clinical Rheumatology.

Earlier diagnosis and treatments have markedly improved outcomes for AAV patients, the study noted. But aggressive use of immunosuppressive agents, which can be needed to manage the disease, puts patients at high risk of infections, a leading cause of death in this disease.

Because types of infectious agents and predisposing risk factors vary across ethnic groups, the researchers decided to explore infections in AAV patients in China, a little studied population.

They retrospectively examined the infectious profile of 207 AAV patients followed at their center, the First Affiliated Hospital of Sun Yatsen University, from 2012 to 2017.

Most (63.6%) had been diagnosed with renal-limited vasculitis — meaning that the disease was contained to their kidneys, followed by microscopic polyangiitis (29.5%), granulomatosis with polyangiitis (3.8%), and eosinophilic granulomatosis with polyangiitis (3%).

The study included 132 patients with infections (63.8% of these 207 people), with an average age of 56. Most infections (72.7%) happened within the first six months of diagnosis, and in patients with active disease (92.4%).

The kidneys and lungs were the most affected organs, and were also common sites of infections. Among a total of 174 cases of infection, 59.2% were in the lungs, 15.5% in the upper respiratory tract, and 5.7% in the urinary tract. Another 14.4% were generalized infections, with most (80%) affecting the lung.

While bacteria — especially gram-negative bacteria — were the major infectious agent (accounting for 75.9%), 6.3% of these cases were caused by fungal infections; 2.3% were viral infections; and 14.9% were mixed, or caused by a two or more pathogenic agents, more commonly bacteria and fungi.

Among the 132 patients with infections, 17 died (12.9%) — 13 within six months of being diagnosed with AAV. Lung infections were the most common cause of death (9 cases), followed by blood infections (3), rapidly progressive damage to filters inside the kidneys (3), and bleeding in lung’s air exchange sacs (2).

Patients who smoked had higher rate of infections (32.6%) than non-smokers (17.3%), and the study also found kidney involvement, dialysis, and low white blood cell counts more common in infection cases. A later statistical analysis attributed each of these factors to a greater likely of infection in AAV patients.

Treatment with glucocorticoids was higher among patients with an infection (51.5% vs. 34.7%), especially use of intravenous methylprednisolone.

“Infection prevailed as a major complication in patients with AAV” in Southern China, the study concluded. “Gram-negative bacteria,” particularly treatment-resistant P. aeruginosa and A. baumanii, “were the leading causative agents. Mixed infection was noticeable. Most of the infection occurred during the first 6 months after AAV onset with high mortality.”

“Early recognition and prompt application of antimicrobials could interfere the poor outcomes of AAV related to infection,” it added.

But its researchers noted that their findings were drawn from patients treated at one hospital, so “interpretation of the results to the general AAV population is cautious.”