Neuropathic-like pain in psoriatic arthritis: evidence of abnormal pain processing

OBJECTIVES: The primary objective was to investigate the prevalence of neuropathic-like pain in patients with psoriatic arthritis (PsA). Secondary outcomes were to investigate whether mood, fatigue, pain, disease severity and fibromyalgia are associated with neuropathic-like pain in PsA patients. METHODS: PsA patients were assessed for fatigue, mood, pain, disease activity and fibromyalgia using questionnaires. Neuropathic-like pain was assessed by PainDetect. RESULTS: Sixty-four patients with PsA were recruited from the Rheumatology Outpatient Department. Of the 64 patients recruited, 26.6% had ‘likely neuropathic pain’ and 21.9% had ‘possible neuropathic-like pain’ according to the PainDetect questionnaire. Patients with ‘likely neuropathic pain’ had higher disease activity, health assessment questionnaire, patient global self-assessment score, tender and swollen joint counts, dactylitis, enthesitis, pain severity and interference with day-to-day activities, fatigue severity and impact, fibromyalgia, anxiety and depression than ‘unlikely neuropathic pain’ patients (p < 0.05). PainDetect score correlated with measures of disease activity, fatigue, depression, anxiety, Widespread Pain Index and Symptom Severity Scale (all p < 0.05). Most patients (71%) with neuropathic-like pain fulfilled American College of Rheumatology 2010 fibromyalgia criteria. Patients with ‘possible neuropathic-like pain’ had scores between patients with ‘likely neuropathic pain’ and ‘unlikely neuropathic pain’. CONCLUSION: Neuropathic-like pain as evidence of abnormal pain processing is common in patients with PsA. It is associated with higher disease activity and fibromyalgia. A significant proportion of patients had ‘possible neuropathic-like’ pain with intermediate disease and symptom score suggesting neuropathic-like pain as evidence of abnormal pain processing is a continuum rather than concurrent fibromyalgia.