Background/Purpose:  To investigate the long-term outcomes and prognostic factors for pts with juvenile-onset idiopathic inflammatory myopathies (JIIM) who are currently adults.

Methods: Adults with JIIM were assessed at two referral centers between 1994 and 2016. Predictor variables included demographics, clinical symptom scores, disease course, worst ACR functional status, drug therapies and co-morbid conditions. Outcomes included physician global activity (PGA) and damage (PGD), Myositis Damage Index (MDI), HAQ, muscle strength testing (MMT26), and total number of drugs at last visit. The analysis was done in GraphPad Prysm (version 7.0a).

Results:  Forty-nine pts with probable or definite JIIM (42 dermatomyositis, 5 polymyositis, 2 overlap myositis) had a median age of 22 yrs. and median disease duration of 11 yrs.; 47% were Caucasian, 82% female. Among these, 55% had a chronic course, 31% polycyclic,10% a monocyclic illness course, 4% undefined. Review of treatment revealed past use of daily prednisone in 84% and current use in 58%; 56% received IV steroids in past and 16% still required IV steroids. Methotrexate (MTX) was the most commonly used DMARD with 79% receiving it in the past and 40% with continued use; 32% used biologics or cytotoxic therapies and 7% remained on these. Median assessment scores at final visit included PGA 1.6 of 10 [IQR 1.0-3.7]; PGD 3.0 [IQR 2-4.4], HAQ 0.4 of 3, and MMT26 229 of 260 [IQR 212-257]. Damage was present in 96% with a median MDI score of 7 [IQR 4-10]. Cutaneous (80%) and muscle (78%) damage were most frequent and most severe (median cutaneous 3 [IQR 1-5], muscle 2 [IQR 1-3]). The most frequent damage features included persistent weakness (71%), muscle dysfunction (68%), contractures (67%), cutaneous scarring/atrophy (61%), calcinosis (57%), muscle atrophy (49%), and lipodystrophy (32%). The most frequent co-morbid conditions included hyperlipidemia (18%), depression or anxiety (18%), and fibromyalgia (6%). Significant univariable predictors of cutaneous damage included disease duration, ACR functional class and prior use of MTX (p 0.016–0.046), whereas for muscle damage, predictors included the past muscle symptom score, earlier year of diagnosis, and prior MTX use (p=0.004-0.025). Predictors of total MDI score included past GI symptom score, younger age at diagnosis, disease duration and ACR functional class (p=0.0004-0.032). Predictors of final PGA scores included past GI and pulmonary symptom scores, chronic disease course, and past use of biologics/cytotoxics (p=0.007-0.028). Pts were receiving a greater number of drugs at last visit if they were younger at time of enrollment, had a shorter disease duration, and had co-morbid depression or anxiety (p=0.0001-0.033).

Conclusion:  This is one of the largest cohorts of patients with JIIM evaluated for long-term outcomes. Our results showed the majority of JIIM pts in this referral-based population have ongoing disease activity and significant disease damage, especially in the cutaneous and muscle systems, and frequent use of prednisone and other drug therapies as adults. Predictors of poor outcomes included disease duration, medication usage, and clinical symptom scores.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/long-term-outcomes-and-their-predictors-in-patients-with-juvenile-idiopathic-inflammatory-myopathies-of-adult-age-a-referral-population-study/