Treatment of Clinically Amyopathic Dermatomyositis in Adults

A Systematic Review

J. Callander; Y. Robson; J. Ingram; V. Piguet

Disclosures

The British Journal of Dermatology. 2018;179(6):1248-1255. 

In This Article

Abstract and Introduction

Abstract

Clinically amyopathic dermatomyositis (CADM) affects a subset of 5–20% of patients with dermatomyositis and is defined as the presence of cutaneous features of dermatomyositis without clinical muscle weakness for ≥ 6 months. There is no consensus on first-line treatment for CADM and whether treatment should differ from treatment of classic dermatomyositis with muscle weakness. We carried out a systematic review of published literature about treatment of adult patients with CADM, via the Embase, Medline, CINAHL and ClinicalTrials.gov databases on 17 February 2015. The aim was to establish which treatments have been used for adult-onset CADM and what evidence is available regarding the efficacy of these treatments including topical treatments, dapsone, antimalarials, intravenous immunoglobulin (IVIG), nonsteroidal oral immunosuppressants and biological therapies. Eighteen cases series and 42 case reports were found. These provided data on 153 adult patients who met the inclusion criteria. No randomized controlled trials or robust observational studies were found. The majority of patients (60%) had tried more than one treatment due to side-effects or lack of efficacy. Antimalarial agents were the most commonly used treatment type. In the majority of patients (55%), antimalarial treatments were discontinued due to lack of improvement or inability to wean concomitant steroids. IVIG was the treatment that led to improvement or remission in the greatest proportion of patients. Further robust, high-quality studies are needed to assess treatment efficacy in CADM without bias.

Introduction

Amyopathic dermatomyositis (ADM) is a subtype of dermatomyositis that has been increasingly recognized over the past 25 years. It is defined as the presence of cutaneous signs of dermatomyositis with no clinical evidence of muscle weakness or abnormal muscle enzymes for ≥ 6 months.[1,2] While cutaneous signs may precede muscle weakness in classic dermatomyositis, ADM does not seem to progress in this way. At present, ADM is not included in the diagnostic criteria for dermatomyositis, originally created in 1975 (Table 1).[3,4]

More recently, the term 'clinically amyopathic dermatomyositis' (CADM) has been coined. It includes patients with no clinical muscle weakness but with evidence of myositis on investigation (hypomyopathic dermatomyositis), as well as patients without clinical muscle weakness or evidence of myositis on investigation (ADM).[5–7] The CADM category has allowed skin-only and skin-predominant disease to be studied independently of classic dermatomyositis. The reported incidence of CADM is between 5% and 20% in patients with dermatomyositis, although it may be underdiagnosed.[8,9]

A systematic review of patients with adult-onset CADM in 2004 identified 291 cases.[5] The authors found that, as with dermatomyositis, most patients were female and white. Overall 14% were associated with underlying malignancy, 13% developed muscle weakness after 6 months and 13% developed interstitial lung disease (ILD). A small proportion of patients with CADM developed rapidly progressive ILD associated with the onset of the rash.[5] Several studies of Asian patients have also found that CADM is associated with higher rates of acute ILD, and that CADM-associated ILD has a poorer prognosis than dermatomyositis-associated ILD.[10–14]

In 2005, the CADM140 antibody and the related autoantigen, melanoma differentiation associated gene (MDA)5, were identified as being closely associated with CADM.[15,16] MDA5 antibodies have been found exclusively in CADM (50–73%) and dermatomyositis (11–25%).[17,18]

Despite increasing knowledge about CADM there is little consensus about treatment.[19] The aim of this systematic review is to establish which treatments have been used for CADM and what evidence is available regarding the efficacy of these treatments.

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