Recurrence of axial spondyloarthritis among first-degree relatives is high, find researchers who call for a greater emphasis on patient education and counselling of family members. 

The Swiss AS family study spanning 35 years and involving 363 ankylosing spondylitis (AS) probands and 806 first degree relatives found the lifetime recurrence rate for HLA-B27 positive first degree relatives to be 27.1%(95% CI 20.6% to 33.7%).  

The study also revealed that the children of female probands were more often affected (12/22; 54.5%) than children of male probands (15/78; 19.2%) (p=0.0003; OR=4.89; 95%CI 1.96 to 12.23).

“Since in clinical practice, AS occurs more often in men, the genetic threshold for women to develop AS might be higher (they seem to be genetically ‘enriched’ with disease susceptibility genes) and that higher genetic load increases the recurrence of disease among both their sons and daughters,” the study authors speculated in their paper published in RMD Open. 

Furthermore, HLA-B27 positive AS probands were significantly more likely to have radiographic axSpA than HLA-B27 negative probands.

According  to the authors, the recurrence rate of axSpA in children of HLA-B27 positive nr-axSpA probands (1/25=4%) was similar to the prevalence of AS among HLA-B27 carriers in the general community, “suggesting that the nr-axSpA itself carries little additional familial risk other than HLA-B27 in those that carry this allele”.

The study authors acknowledged that limitations of their study included the potential for ascertainment and selection bias. Nevertheless, they noted that the substantially high lifetime recurrence rate of axSpA for first degree relatives of AS probands necessitated a greater emphasis on patient education and counselling.

“These findings may lead to better assessment of lifetime risk for axSpA in the offspring. Moreover, investigation of this gender effect may uncover additional putative disease susceptibility factors,” they added.