Background/Purpose: To evaluate features of JIIM clinical and Ab subgroups at illness onset. 

Methods: Physician-completed questionnaires illness onset features were reviewed in 465 JIIM pts (381 juvenile dermatomyositis [JDM], 33 polymyositis, [JPM], and 51 JIIM associated with other autoimmune diseases [JCTM]) meeting probable or definite Bohan and Peter criteria. Myositis Abs were tested by standard immunopreciptation and blotting methods. Univariate analysis was performed using GraphPad Prism 5.0.

Results: The first weakness was proximal in all clinical and Ab subgroups (86-90%). Gottron’s papules were most often the first rash in JDM and JCTM (48% and 47%), followed by heliotrope (45% and 29%), and malar rash (30% and 14%). Gottron’s papules were also the first rash in 57% of pts with anti-p155/140, 50% of anti-Mi2, 40% of anti-MJ and 32% of pts with anti-ARS Abs (P < 0.04). Heliotrope was most often the first rash in pts with anti-MJ (52%) and anti-ARS (47%). Both Gottron’s papules and heliotrope were present at diagnosis in 72% of JDM and 58% of JCTM pts. Gottron’s papules or heliotrope alone were seen in 18% and 9% of JDM pts at diagnosis, yet 1.7% of JDM patients did not have either rash at diagnosis. 81% of pts with anti-p155/140 Abs had both Gottron’s and heliotrope at diagnosis. Rash before weakness was seen in 54% of JDM and 74% of JCTM pts. Weakness before rash was seen in 23% of JDM and 14% of JCTM pts; 23% of JDM and 12% of JCTM pts developed rash and weakness simultaneously. Rash before weakness was observed in 73% of pts with anti-p155/140, 67% of anti-Mi2, 39% of anti-MJ, and 39% of anti-ARS Ab pts (P <0.04). Weakness before rash was observed in 33% of anti-ARS, 31% of anti-MJ, 17% of anti-Mi2 and 12% of anti-p155/140 pts (P < 0.02). All JIIM pts had a median delay to diagnosis of 4.1 mo and JCTM pts had delay of 7.1 mo (P < 0.03); pts with anti-p155/140 had a median delay of 4.8 mo, anti-ARS 6.6 mo, and anti-SRP Abs 2.0 mo between first symptom and diagnosis. The median time between rash and diagnosis was 2.5 mo in JDM, 6.1 mo in JCTM, 4.0 mo in anti-p155/140 and 1 mo in anti-ARS Ab groups (P < 0.007). Twenty-three percent of JIIM pts had one and 5.7% had ≥ 2 misdiagnoses. Common misdiagnoses included infections (9.6%), other autoimmune diseases (4.6%), musculoskeletal (2.4%) and dermatologic conditions (17.6%), neurologic diseases (1.5%), and psychologic disorders (0.7%). JPM and pts with anti-SRP Abs were often misdiagnosed with hepatitis (15.2-28.6%) and neurologic conditions (9.1%) including Guillain-Barre (3-14%). Pts with JDM and JCTM, including those with p155/140 and MJ Abs, were often misdiagnosed with other skin conditions (11-21%), including eczema (11-21%).

Conclusion: JIIM clinical and Ab groups vary in their type of rash and weakness and misdiagnosis at illness onset. Most present with rash before weakness, and with Gottron’s papules first.  Better recognition of these varied presentations of illness should enhance recognition of JIIM phenotypes and help decrease delay in diagnosis and therapy.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/illness-onset-features-and-misdiagnosis-in-juvenile-idiopathic-inflammatory-myopathies-jiim-differ-among-clinical-and-autoantibody-ab-subgroups/