Investigating persistent bilateral ankle swelling

Abstract

This paper presents a case-report of a young female reporting sudden onset ankle swelling and pain, subcutaneous inflammation and progressive bilateral pes planus, in the context of no associated co-morbidities or risk factors for autoimmune and infective conditions. We discussed the appropriate imaging techniques which facilitated the diagnosis, which included Xrays, ultrasound and MRI scans used to rule out soft tissue injuries, stress fractures, inflammatory arthritis, and other causes of peripheral nerve entrapment and tendon pathology. The patient was diagnosed with polyarteritis nodosa based on deep skin biopsy. This is the first case ever reported showing significant peripheral nerve enlargement in the context of small vessel vasculitis.The imaging step-up approach is discussed in relation to the sensitivity and specificity of different imaging techniques for assessing joint, bone, tendon, ligament and nerve-related pathology. The rarity of this diagnosis in the context of a very common presentation emphasised the need for specialist referral and has significant educational value.