The association between refractory plantar fasciitis and insertional Achilles tendinopathy and peripheral spondyloarthritis: a report of human leukocyte antigen B-27 investigation and treatment outcome.

PURPOSE: This study aimed to determine the presence of peripheral spondyloarthritis and investigate the clinical characteristics of patients with concurrent peripheral spondyloarthritis in those presenting with refractory plantar fasciitis and Achilles tendinopathy by conducting human leukocyte antigen B-27 (HLA-B27) testing. METHODS: This retrospective study aimed to investigate patients who complained of persistent pain and significant limitations in daily activities due to their respective foot pain, despite receiving conservative treatment for over one year under the diagnosis of plantar fasciitis or insertional Achilles tendinopathy. The study included 63 patients who underwent HLA-B27 testing. The patients were classified into two groups based on the presence or absence of HLA-B27 positivity. The Mann-Whitney U test assessed significant relationships between continuous variables, and the chi-square test was used to compare categorical variables. RESULTS: Among the 63 included patients, HLA-B27 positivity was confirmed in 11 patients (17.5%), which was significantly associated with a lower average age (22.8 years versus 31.7 years, P = 0.01) and a substantially lower proportion of females compared to HLA-B27-negative patients (9.1% vs. 25.0%, P = 0.001). Ten of the 11 patients initiated treatment with conventional synthetic disease-modifying antirheumatic drugs (DMARDs) combined with oral steroids as the first-line medication after being diagnosed as HLA-B27 positive. Six patients experienced pain relief with the first-line medication (60%). Four patients who did not achieve pain control with the first-line medication received tumour necrosis factor-alpha inhibitors as the second-line medication. Two patients experienced pain relief, while two experienced reduced but persistent pain. CONCLUSIONS: Among the patients with "refractory" plantar fasciitis and insertional Achilles tendinopathy, 17.5% were diagnosed with peripheral spondyloarthritis. Patients diagnosed with peripheral spondyloarthritis had a higher proportion of men and relatively younger mean age compared to those without the diagnosis. Approximately 70% of these patients achieved symptom improvement in foot and ankle joints by taking conventional synthetic DMARDs, TNF-α inhibitors, or both appropriate for spondyloarthritis.