Background Up to 50% of cases of juvenile spondyloarthritis (JSpA) begin in childhood, with clinical features that distinguish them from their adult counterparts, such as more frequent peripheral involvement, and more severe and disabling outcome. Although descriptions of JSpA in worldwide different populations are scarce, it has been suggested that clinical expression could different in Spanish and Mexican populations.
Objectives To compare the pattern of musculoskeletal involvement among Spanish and Mexican patients with JspA.
Methods We conducted a descriptive study based on baseline data of MexESpA study, comprising a binational cohort distributed in 10 Spanish centers (n = 95) and 6 Mexican (n = 33). Analyzed data were demographic characteristics, musculoskeletal manifestations, metrology, HLA-B27 and diagnosis.
Results 65% of Spanish children were boys, while in Mexico were 85%. Mean age at onset was higher in Mexican population (12 ± 3 years) than Spanish (10 ± 4 years), with a greater duration of symptoms in the latter group. 94% of Spanish patients were Caucasian, while in Mexico predominated white-Indian (64%). Frequency of HLA-B27 was higher in Spain (47%) than Mexico (27%), as well as family history of SpA (45% and 18%, respectively). Almost all children in both countries had some type of musculoskeletal symptom (95% in Spain and 94% in Mexico). However, the pattern was different between both countries. In Spain predominated peripheral arthritis affecting lower extremities and in Mexico peripheral enthesitis, followed by peripheral arthritis and inflammatory pain. No differences in the number of tender, swollen or limited joints. In Spain 9% had some axial entheses affected and 44% some peripheral, while in Mexico, these percentages were much higher, 36% and 85% respectively. No significant differences were found in metrology and average modified Schober in both populations was 6 cm. There was also no significant difference in the C-HAQ, or BASDAI and BASFI indexes, although values were slightly higher in Mexico. Among the diagnoses at baseline, more patients in the Mexican cohort had ankylosing spondylitis in (61%) than in the Spanish (7%), and conversely, undifferentiated and psoriatic JSpA were more prevalent in the Spanish patients (46% and 36%, respectively) than in Mexicans (36% and 3%, respectively).
Conclusions Results show a different pattern of musculoskeletal involvemente between Spain and Mexico. Differences could be related to several aspects including social and environmental factors, age of onset and different JSpA subtypes. However, probably the main explanatory factor is genetic background, with a higher frequency of HLA-B27 in Spanish patients, while there is a stronger association with HLA-DRB1*08 and LMP-2 in Mexican patients, which predispose to more severe manifestations in this group.
Disclosure of Interest None Declared