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Phenotype Phebrurary 2023 - P7 - Adult dermatomyositis

Hello! My name is Chris Mecoli; a bit of background – I work as a rheumatologist at Johns Hopkins in our Myositis Center. I’m joined by Zach Wang (data science graduate student) and Will Kelly (database manager) who bring their data science expertise to this project. We are all relatively new to OHDSI, and are excited to increase our involvement. Thanks to @Gowtham_Rao et al for holding an interactive session to help review our phenotype. Now, on to the Phenotype of interest: Adult Dermatomyositis.

Adult Dermatomyositis

Develop a shared clinical understanding of the phenotype

Adult Dermatomyositis (DM – not diabetes!) is a rare disease (estimated incidence 10 cases per million people) that causes muscle inflammation and skin rash. It’s one of a group of muscle diseases that cause muscle inflammation and swelling. It’s different from other muscle diseases because it also causes skin problems. Dermatomyositis is the term used to describe both muscle and skin symptoms. Because of the heterogeneity of this condition, often times many different providers/specialists will care for DM patients, including rheumatologists, neurologists, primary care physicians, pulmonologists, and dermatologists. DM can occur at any age, but it most often affects adults ages 50 to 70. Women are twice as likely as men to be diagnosed with the disease. The symptoms include rashes throughout the body, proximal muscle weakness, trouble swallowing (dysphagia), muscle pain (myalgia), difficulty breathing (dyspnea), and joint pains (polyarthralgia).

How is dermatomyositis diagnosed?

No single test can make the diagnosis of DM; rather, it is the entire clinical picture of history, physical examination, blood work and ancillary testing. The most common blood tests include the muscle enzyme ‘creatine kinase’ and myositis-specific autoantibodies (e.g. Jo1, SAE, Mi2). Additional studies performed often include an electromyelogram (EMG), muscle MRI, and skin or muscle biopsy.

How is dermatomyositis treated?

There’s no cure for the condition, but the symptoms can be managed. Essentially all patients receive some form of immunosuppression (drugs such as prednisone, methotrexate, mycophenolate, azathioprine rituximab, intravenous immunoglobulin, and several others).

What is the prognosis?

DM is often a chronic condition lasting many years, although in a minority of patients, drug-free clinical remission can be achieved. The majority of patients will require monitoring and long-term treatment with some form of immunosuppressive/immunomodulatory therapy.

Differential diagnosis

Often on the list of DM mimics includes other rheumatic diseases such as systemic lupus erythematosus and systemic sclerosis. In addition, dermatologic diseases such as atopic dermatitis (eczema) and psoriasis can mimic dermatomyositis. Lastly, other forms of myositis (polymyositis, immune-mediated necrotizing myopathies) are considered when evaluating a patient for DM.

The goal of this phenotype is to study incident DM cases in any health care setting (inpatient, outpatient, ER).

Literature Review of DM in Observational Research

Several research groups have studied DM patients in observational research using diagnosis codes. The majority of these studies use ICD-9/ICD-10 codes for “dermatomyositis” – specifically codes 710.3 (ICD-9) and M33xxx (ICD-10). DM patients can be seen in any context (inpatient, ER, outpatient), and have been studied in all of these locations. Very few prior studies have incorporated other criteria beyond diagnosis codes (such as whether a specialist saw the patient, or whether the patient received corticosteroids/prednisone or underwent a muscle biopsy).

Pavon MR, Sanchez JE, Pescatore J, Edigin E, Richardson C, Manadan A. Reasons for Hospitalization and In-Hospital Mortality in Adults With Dermatomyositis and Polymyositis. J Clin Rheumatol. 2022 Mar 1;28(2):e433-e439. doi: 10.1097/RHU.0000000000001754. PMID: 34262001.

Kwa MC, Ardalan K, Laumann AE, Nardone B, West DP, Silverberg JI. Validation of International Classification of Diseases Codes for the Epidemiologic Study of Dermatomyositis. Arthritis Care Res (Hoboken). 2017 May;69(5):753-757. doi: 10.1002/acr.23010. PMID: 27564726.

Yafasova A, Diederichsen LP, Schou M, Sun G, Torp-Pedersen C, Gislason GH, Fosbøl EL, Køber L, Butt JH. Increased long-term risk of heart failure and other adverse cardiac outcomes in dermatomyositis and polymyositis: Insights from a nationwide cohort. J Intern Med. 2021 Sep;290(3):704-714. doi: 10.1111/joim.13309. Epub 2021 Jun 3. PMID: 34080737.

Dobloug C, Garen T, Bitter H, Stjärne J, Stenseth G, Grøvle L, Sem M, Gran JT, Molberg Ø. Prevalence and clinical characteristics of adult polymyositis and dermatomyositis; data from a large and unselected Norwegian cohort. Ann Rheum Dis. 2015 Aug;74(8):1551-6. doi: 10.1136/annrheumdis-2013-205127. Epub 2014 Apr 2. PMID: 24695011.

Smoyer-Tomic KE, Amato AA, Fernandes AW. Incidence and prevalence of idiopathic inflammatory myopathies among commercially insured, Medicare supplemental insured, and Medicaid enrolled populations: an administrative claims analysis. BMC Musculoskelet Disord. 2012 Jun 15;13:103. doi: 10.1186/1471-2474-13-103. PMID: 22703603; PMCID: PMC3480956.

Building a Cohort Set Expression

DM diagnostic and classification criteria exist that are considered the ‘gold standard’ for defining DM cohorts. The two most common diagnostic/classification criteria used in research are referred to as “Bohan and Peter” established in the 1970s and the ACR/EULAR 2017 Classification Criteria. However, the criteria in each are typically not available in most EHR or claims data sets (e.g. concepts such as “Gottron’s sign”, “proximal muscle weakness”, “elevated CPK levels”, and “myopathic findings on electromyogram” are rarely coded as such).

It is likely that only consortia/registries that specialize in Myositis will have this level of detail within their OMOP data (custom concepts would need to be created and mapped to OMOP standard vocabulary). For datasets that do not have this level of granularity, an alternative approach is needed. Therefore, we constructed two cohort definitions for adult DM patients, one to maximize sensitivity, one to maximize specificity, depending on the research question. These will be included in a follow-up post leading into the weekend.

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Thanks @Christopher_Mecoli for your leadership and particiapation, I really look forward to learning about the other DM :slight_smile: Given that the symptoms and treatments are both largely non-specific, I’ll be curious to see how the evaluation results play out, particularly if we’re able to run PheValuator @jswerdel .

Video recording Phenotype Phebruary 2023 Discussion: Inflammatory Myopathieis - YouTube

In this video recording, Christopher Mecoli, MD, and team demonstrated progress in the development of a cohort definition for Inflammatory Dermatomyositis at Johns Hopkins University. The team discussed their experience running Cohort Diagnostics, and reviewed the results on data.ohdsi.org. They discussed the impact of design choices, specifically the use of lab values in cohort definitions. Decisions were made to improve the cohort definition logic.

OK apologies for the delay! Here it is:

We developed two phenotypes for adult DM - sensitive cohort ID #302 and specific cohort ID #303.

The sensitive cohort was essentially two separate diagnoses of “dermatomyositis” within one year. We reviewed descendents for each concept ID included in the cohort definition and ensured we were excluding “juvenile” and “childhood” dermatomyositis as our phenotype is focusing on the adult population. We also wanted to exclude “drug-induced dermatomyositis” as this is a different entity than the phenotype of interest.

With the sensitive cohort, the following output was observed across databases (thank you @Gowtham_Rao for the assist):


When run against our own Hopkins Myositis Database, this resulted in N=794, which is a very good approximation (we have about 820 adult DM patients enrolled per gold standard chart review).

In taking a deeper dive at demographics:

This looks good! We expect this distribution in age and sex given what is known about the epidemiology of adult DM. HOWEVER, clearly there are some patients <18 who are included, which is of course not adult DM. I suspect these are patients with juvenile DM who “aged into” an adult clinic. Alternatively, children with dermatomyositis were simply diagnosed with “dermatomyositis”. We can think about ways of excluding these patients in future iterations of this cohort definition (inclusion >/=18 years old).

One thing that caught my eye is the frequency of the OTHER DM, “diabetes”:

It’s certainly plausible these are real - many older patients have DM, particularly those who have received a lot of prednisone for their adult dermatomyositis. However I do wonder how much cross-reactivity these is between diabetes ‘DM’ and dermatomyositis ‘DM’ from potential coding errors.

With regards to the specific cohort, we attempted to increase specificity by adding requirements for both immunosuppressive medications (used to treat essentially all patients with adult DM) and autoantibodies (adds further confidence of diagnosis, as well as provides a potential pathway to further subgroup dermatomyositis patient populations in future research studies).

However, adding these two inclusion criteria essentially wiped out all cases:


In taking a deeper dive, this appears to largely be related to requiring the antibody test. Based on feedback from our OHDSI calls, there was an idea to separate “test performed” from “test positive”, similar to the approach described in the SLE phenotype this month.

In terms of next steps, we are refining both of our sensitive and specific cohort definitions based on Phenotype Workgroup feedback/Peer Review. The goal will be to finalize these phenotypes within our team, and submit them for further cohort diagnostics and PheValuator with the generous help of @Gowtham_Rao @Joel_Swerdel, @agolozar and others!

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@Christopher_Mecoli for next step, are you OK with focusing on the sensitive definition? I know you are trying to run PheValuator. Should we set a call to fully evaluate the sensitive cohort and push it to peer review as soon as pheValuator results are available?

Hi Chris - would you put the links to the 2 DM phenotypes (#302 and # 303) here in the post?
Thanks - Joel

A short meeting will be held on this phenotype today at 2pm. Meeting invite is here