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ORPHA:221Disease
Also called Adult dermatomyositis
What it is
A rare idiopathic inflammatory myopathy (IIM) characterized by evocative skin lesions, muscle involvement with symmetrical proximal muscle weakness, and specific histological features. The clinical subtypes are defined by the presence of myositis-specific antibodies (anti-Mi2, anti-NXP2, anti-TIF1-γ, anti-MDA5, or anti-SAE antibodies) and are associated with specific clinical phenotypes and prognosis.
Key facts
- Prevalence
- 1-9 / 100 000
- Age of onset
- Adult, Elderly
- Inheritance
- Not applicable
- Classified as
- Disease
Prevalence figures describe populations, not individuals, and are often estimates from a single study. Where the figure is an incidence or a birth prevalence, it says so.
Signs and symptoms
Very common80–99%
8- Autoimmunity
- Edema
- Erythema
- Inflammatory myopathy
- Limb-girdle muscle weaknessDiagnostic criterion
- Myalgia
- Periorbital edema
- Proximal muscle weaknessDiagnostic criterion
Common30–79%
28- Abnormal pulmonary interstitial morphology
- Acrocyanosis
- Anti-SUMO-activating enzyme subunit 1 antibody positivity
- Anti-SUMO-activating enzyme subunit 2 antibody positivity
- Arthralgia
- Arthritis
- Diffuse reticular or finely nodular infiltrations
- Elevated circulating aldolase concentrationDiagnostic criterion
- Elevated circulating creatine kinase concentrationDiagnostic criterion
- Elevated circulating hepatic transaminase concentrationDiagnostic criterion
- EMG: myopathic abnormalitiesDiagnostic criterion
- Facial erythema
- Fatigue
- Gottron's papulesPathognomonic sign
- Heliotrope rashPathognomonic sign
- Hypotonia
- Increased circulating lactate dehydrogenase concentrationDiagnostic criterion
- MyositisDiagnostic criterion
- Papule
- Periungual erythema
- Pruritus
- Pulmonary fibrosis
- Respiratory insufficiency
- Respiratory insufficiency due to muscle weaknessDiagnostic criterion
- Shawl sign
- Skin rashDiagnostic criterion
- Skin ulcer
- Weight loss
Sometimes5–29%
30- Alopecia
- Anti-histidyl tRNA synthetase antibody positivity
- Anti-MDA5 antibody positivity
- Anti-Mi2 antibody positivity
- Anti-nuclear matrix protein-2 antibody positivity
- Anti-SUMO-activating enzyme antibody positivity
- Anti-transcription intermediary factor-1gamma antibody positivity
- Arrhythmia
and 22 more in this range
These ranges are how often a sign appears across everyone diagnosed, not a prediction for one person — most people have some of these and not others. Orphanet also records findings that are specifically absent in this disease; those are in the data but not listed here.
ICD-10 codes
ICD-10 has no distinct code for most rare diseases, so many are filed under the nearest available one. A shared code identifies the group, not this disease — the ORPHAcode above is what identifies it.
Related health topics
Reached through the ICD-10 categories this disease is filed under, so these describe the broader group rather than this disease specifically.
Cross-references
Orphadata Science: Free access data from Orphanet. © INSERM 1999. Data version 2026-06-23. Available under CC BY 4.0. This is a reference, not medical advice.
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