Frequency and clinical and laboratory features of ankylosing spondylitis with secondary AA-amyloidosis

Background. Pathogenesis of ankylosing spondylitis (AS) is based on long-term chronic inflammation, which can lead to the development of secondary amyloidosis.

Aim. To analyze the frequency of secondary amyloidosis in a hospital cohort of patients with AS and describe their clinical and laboratory features.

Materials and methods. Four hundred and fifty eight patients with AS were examined. Patients’ disease activity and functional status were assessed according to the Russian expert recommendations. Additionally, in all patients, SAA in blood serum was determined using nephelometric method. Patients having high laboratory activity during several years underwent fibrogastroduodenoscopy and biopsy of the duodenum submucosal layer, in the absence of contraindications.

Results. Among 458 patients with AS, the diagnosis of AA amyloidosis was confirmed in 21 (4.5%) cases; the frequency among men was 5.6%, among women – 2.6%. In 15 (3.3%) cases, AA amyloidosis was diagnosed for the first time, and only in 6 (1.3%) patients it was diagnosed before. Patients with AA-amyloidosis had higher disease activity measured by ASDAS-CRP and higher ESR values. Patients with amyloidosis had higher frequency of syndesmophytes and they underwent joint arthroplasty more often compared to the control group. Among the patients with amyloidosis, a significant negative association was revealed between the patients’ age of enrollment in the study and the presence of arthritis, the values of BASDAI and ASDAS indices. The following associations were not observed in the control group. We did not find the expected association between SAA and activity scores, these values did not differ between groups.

Conclusion. In a specialized rheumatology department, the frequency of AA-amyloidosis in patients with AS reaches 4.5%. Amyloidosis significantly more often develops in males, in patients with juvenile onset, in the late stage of the disease, in patients with high disease activity. Without a targeted search for secondary amyloidosis in patients with AS, its detection rate in real clinical practice is about 30%.