Prevalence and clinical features of Arthritis Mutilans (AM) patients attending a Dublin rheumatology unit
Musaab Elmamoun (1), Muhammad Haroon (2), Phil Gallagher (1), Oliver FitzGerald (1)
1. Department of Rheumatology, St. Vincent’s University Hospital, Dublin, Ireland, 2. Department of Rheumatology, Kerry General Hospital, Tralee, Ireland.
Psoriatic Arthritis (PsA) affects about 30% of individuals with psoriasis after an average interval of 10 years1, 2. AM is a rare type of PsA. The prevalence of AM has been estimated to range from zero or just 1%3, 4 to up to 8%5 of the PsA population.
To determine the demographic and clinical characteristics of AM in an Irish cohort attending a rheumatology unit.
Patients with a diagnosis of PsA, fulfilling the CASPAR criteria, who have AM were included. AM was defined by digital shortening, erosion involving entire articular surfaces on both sides of the joint and/or pencil-in-cup change and/or osteolysis. 23 patients, aged > 18 years were included after clinical and radiological examination.
The female to male ratio was close to 2 : 1. The mean age was 56.52. The mean age of skin disease onset was 24 years and the mean age of onset of joint disease was 30 years. At inclusion, the mean duration of arthritis was 25.8 years ± 9.9 years. The only pattern of arthritis observed in patients with AM was that of polyarticular disease; with 48% of patients exhibiting axial disease. Enthesitis was found in 8 patients (35%), while 13 patients (57%) had dactylitis. 8 patients (35%) had sacroiliitis on plain films, 6 of these patients (75%) had asymmetrical sacroiliitis. 21 patients (91%) had nail disease. None of the patients in this cohort had uveitis. At the time of inclusion, 70% of patients were found to have clear or almost clear skin. 16 patients were on biologics (75%). The most frequent joints that showed AM were the MTP joints on the fourth toe on the left foot (n = 10), followed by MTP joints on the fourth toe on the right (n = 9). Further characteristics are outlined in table 1.
The prevalence of AM in our psoriatic arthritis cohort (n=282) is approximately 8%. The majority of patients present with nail disease, and mild skin disease. The average interval between skin and joint disease is approximately 6 years. AM occurs in the setting of polyarticular disease and frequent axial involvement. The axial disease in these patients tends to be asymmetrical. Many patients require biologics to control their disease.
Table 1 Patients’ characteristics
BMI Body Mass Index; RF, rheumatoid factor; ACPA, anticitrullinated protein antibody; Ps, psoriasis; PsA, psoriatic arthritis; BSA, Body Surface Area; PASI, Psoriasis Area Severity Index; CRP, C-Reactive Protein; mHAQ modified Health Assessment Questionnaire