Application of a Diagnostic Algorithm to Identify Inflammatory Myopathy in Systemic Sclerosis

Vandana Bhushan^1,2, Adam Maundrell¹, Charlotte Proudman^1,2, Leah McWilliams¹, Llew Spargo¹, Robert Metcalf¹, Jennifer Walker³, Mandana Nikpour^4,5, Wendy Stevens⁴, Vidya Limaye^1,2 and Susanna Proudman^1,2, ¹Rheumatology Unit, Royal Adelaide Hospital, South Australia, Adelaide, Australia, ²Discipline of Medicine, University of Adelaide, South Australia, Adelaide, Australia, ³Flinders University of South Australia, Adelaide, Australia, ⁴St Vincent's Hospital, Melbourne, Victoria, Melbourne, Australia, ⁵Department of Medicine, University of Melbourne, Victoria, Melbourne, Australia

Meeting: ACR/ARHP Annual Meeting 2017

Date of first publication: September 18, 2017

Keywords: muscle biopsy, Myositis and scleroderma

Session Information

Date: Sunday, November 5, 2017

Title: Systemic Sclerosis, Fibrosing Syndromes and Raynaud's – Clinical Aspects and Therapeutics I

Session Type: ACR Concurrent Abstract Session

Session Time: 4:30PM-6:00PM

Background/Purpose:

Muscle involvement in systemic sclerosis (SSc) is under-recognised and poorly understood. Reported prevalence varies up to 15%, reflecting lack of consistent definition, the heterogeneous spectrum of muscle involvement, ranging from non-specific myopathic changes to idiopathic inflammatory myopathies such as polymyositis, but also lack of a standardised approach to detection. Early diagnosis of inflammatory myopathy by muscle biopsy is important to guide immunosuppressive therapy to minimise irreversible loss of muscle power and function. We sought to determine the prevalence of inflammatory myopathy in patients with SSc assessed annually for features of muscle involvement according to a standardised algorithm.

Methods:

Consecutive patients with SSc, according to the 1980 ACR or LeRoy and Medsger criteria, enrolled in the Australian Scleroderma Cohort Study (ASCS) since 2007, are assessed annually for features of myopathy: proximal muscle weakness based on the Medical Research Centre scale and elevated creatine kinase (CK) > 150 U/L. No specific guidelines for further investigation are followed. In a subset of patients from a single ASCS centre, if proximal weakness and/or elevated CK were present, myositis immunoblot for myositis specific antibodies (MSA) and/or MRI of upper or lower limbs for increased T2 signal or fatty infiltration and atrophy were performed; positive findings prompted a muscle biopsy. Features of patients with and without histopathological features of inflammation on biopsy were compared.

Results:

Among 1197 patients enrolled in the ASCS, 176 (14.7%) had elevated CK with or without weakness at any time during follow up, 128 (10.7%) had weakness with a normal CK, and 18 (1.5%) patients had biopsy-proven inflammatory myopathy. In a separate ASCS cohort of 333 patients in South Australia, 89 of 323 (27.6%) had elevated CK, 83 of 326 (25.5%) had proximal weakness and 34 (10.2%) were selected for muscle biopsy. Abnormalities were present in all 34 biopsies, with inflammatory myopathy (polymyositis, 10; dermatomyositis, 4; inclusion body myositis, 3; necrotising, 1; other, 2) confirmed in 20 (58.8%) and nonspecific features of myopathy reported in 14.

Among the biopsied patients, incidence of diffuse cutaneous subtype and levels of CK were significantly higher in those with inflammatory compared with non-inflammatory myopathy (Table 1). Immunosuppressive use at time of biopsy was similar in the two groups.

Table 1: Characteristics of SSc patients selected for muscle biopsy

	Inflammatory myopathy n = 20	Non-inflammatory myopathy n = 14	P value¹
Diffuse SSc	6	0	0.031
SSc antibodies: ACA Scl70 RNA polymerase III RNP	10/20 3 2 1 4	9/14 2 2 3 2	0.500
Immunosuppressive therapy at time of biopsy	9	9	0.147
Elevated CK	14	7	0.238
CK level U/L (median, IQR)	436 (243-571)	132 (63-383)	0.023²
Proximal weakness	15	11	1.000
Myositis immunoblot +ve: Ro52 Mi-2 Ku PM-Scl75 Jo-1 SRP PL7 PL12	10/17 7 1 1 2 1 1 1 1	4/10 2 0 1 1 1 0 0 0	0.440
Increased T2 signal on MRI muscle	6/7	2/7	0.103

IQR, interquartile range

¹Fisher’s exact test except where indicated. ²Mann Whitney U.

Conclusion:

A diagnostic algorithm including MSA and MRI, detected biopsy-proven muscle involvement in 10.2% of patients with SSc and increased the detection of inflammatory myopathy to 6% of patients compared with 1.5% in the whole ASCS cohort.

Disclosure: V. Bhushan, None; A. Maundrell, None; C. Proudman, None; L. McWilliams, None; L. Spargo, None; R. Metcalf, None; J. Walker, Actelion Australia, Bayer, CSL Biotherapies, GlaxoSmithKline Australia and Pfizer, 2; M. Nikpour, Actelion Australia, Bayer, CSL Biotherapies, GlaxoSmithKline Australia and Pfizer, 2; W. Stevens, Actelion Australia, Bayer, CSL Biotherapies, GlaxoSmithKline Australia and Pfizer, 2; V. Limaye, None; S. Proudman, Actelion Australia, Bayer, CSL Biotherapies, GlaxoSmithKline Australia and Pfizer, 2,Actelion Australia, 8.

To cite this abstract in AMA style:

Bhushan V, Maundrell A, Proudman C, McWilliams L, Spargo L, Metcalf R, Walker J, Nikpour M, Stevens W, Limaye V, Proudman S. Application of a Diagnostic Algorithm to Identify Inflammatory Myopathy in Systemic Sclerosis [abstract]. Arthritis Rheumatol. 2017; 69 (suppl 10). https://acrabstracts.org/abstract/application-of-a-diagnostic-algorithm-to-identify-inflammatory-myopathy-in-systemic-sclerosis/. Accessed .

ACR Meeting Abstracts - https://acrabstracts.org/abstract/application-of-a-diagnostic-algorithm-to-identify-inflammatory-myopathy-in-systemic-sclerosis/