Ankylosing spondylitis and a diagnostic dilemma: coccydynia

Coccydynia is defined as pain in or around the tail bone area. The most common cause of coccydynia is either a trauma such as a fall directly on to the coccyx or repetitive minor trauma. The etiology remains obscure in up to 30% of patients. The literature on the contribution of rheumatic diseases to coccydynia is scarce. Our objective was to investigate the prevalence of coccydynia in ankylosing spondylitis (AS) patients.

One hundred and seven consecutive patients with AS were evaluated for coccydynia were enrolled between January and November 2012 for a cross-sectional analysis. Seventy-four consecutive patients were followed for mechanical back pain as controls and the AS patients were interviewed for the presence of coccydynia. The data collected was evaluated on SPSS® version 11.5 and Microsoft Excel® Programmes.

Prevalence of coccydynia in AS (38.3%) was significantly higher than the control group (p<0.0001) in both female and male AS patients (female AS vs. control=40.9% vs. 18.4%, p=0.015 and male AS vs. control=36.5% vs. 8.0%, p=0.005). Both genders were affected equally in the AS group whereas coccydynia was slightly more frequent in female patients in the control group.

Coccydynia is a previously neglected symptom of AS and it is almost three times more common in AS than in non-specific chronic low back pain. Our observation may implicate that inflammatory diseases have a role in the etiology of coccydynia, especially in those without a history of recent or past trauma and coccydynia may be a factor associated with the severity of AS as well.