Winter Rise in Renal AAV Cases, Possibly Due to Infections, Reported in Study

Patients are more likely to develop anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) that affects their kidneys in the winter months, likely due to environmental factors that promote disease-triggering infections, a study reports.

The study, “Seasonal variations in the onset of positive and negative renal ANCA-associated vasculitis in Spain,” was published in the journal Clinical Kidney Journal.

Researchers suspect that both genetic and environmental factors contribute to the development of AAV, and have widely studied potential genetic factors, but less work has been done on those that may originate in an environment.

Some of these environmental studies have shown an increase in AAV incidence in patients exposed to certain air pollutants or treated with certain drugs. Infection by bacteria, such as Staphylococcus aureus, is also linked with granulomatosis with polyangiitis (GPA) development.

In fact, many of these studies report that AAV rates tend to vary by the season, with a peak in winter. Some, however, have shown a climb in AAV rates in summer months in GPA patients.

Because of these differing reports, a group of Spanish researchers set out to assess seasonal variation in cases of renal AAV.

They retrospectively analyzed 234 patients in Catalonia who were diagnosed with renal AAV between 2001 and 2014. They looked at the date of first AAV symptoms, subtypes of ANCA (positive or negative), degree of renal damage, and renal histology.

Results showed a clear seasonal preference, with a significantly higher incidence of new AAV cases in the winter. Researchers conducted statistical analysis and showed that AAV incidence fluctuated around an “annual cycle, with peaks” every 10 to 12 months, and a higher number of cases in February.

When looking at ANCA subtypes, researchers found that there was lower incidence of AAV symptoms in the spring for patients that were ANCA-negative, suggesting possible differences in environmental triggers for ANCA-positive and negative patients.

“Our results in a cohort of AAV patients with renal affectation in Spain confirm a periodic fluctuation and seasonal variation of AAV, as described in the literature, with higher incidence in the winter,” the researchers concluded. “These results make it plausible that environmental factors, most likely an infection trigger, act as activators for the development of the disease.”