Dermatomyositis is a chronic inflammatory disorder of the skin and muscles that is characterized by an autoimmune pathogenesis. It commonly presents with characteristic rashes like Gottron's papules and heliotrope rash as well as proximal muscle weakness. Dermatomyositis can also involve internal organs like the lungs, esophagus and heart. Diagnosis involves assessing clinical features, muscle enzymes, electromyography, muscle/skin biopsies and identifying myositis-specific antibodies. Prognosis depends on the severity and organ involvement, with risks of residual weakness, contractures and death from respiratory or cardiac complications.

1. DERMATOMYOSITIS

2. DERMATOMYOSITIS
 Dermatomyositis (DM) is a chronic inflammatory disorder of the skin and
muscles.
 An autoimmune disease
 Skin involvement in DM usually manifests with characteristic papules over digits,
erythema over the elbows and knees, a heliotrope rash around the eyes,
periungual telangiectasias, and dystrophic cuticles.
 Muscle involvement usually manifests as proximal muscle weakness initially,
with or without myalgias or tenderness.

3. AMYOPATHIC DERMATOMYOSITIS
 Amyopathic dermatomyositis can be a challenging diagnosis because patients lack
traditional muscle findings.
 "Clinically amyopathic" dermatomyositis (CADM) accounts for the presence of
subclinical muscle disease in some of these patients.
 These patients represent a substantial minority of dermatomyositis cases and have
similar co-morbidities to "classic" dermatomyositis patients, including interstitial lung
disease and malignancy.
 Clinically amyopathic dermatomyositis patients should not be considered as a distinct
clinical entity from "classic" dermatomyositis, as they share antibody sub-types and
associated co-morbidities, likely representing clinical spectrum of a common disease.

4. DESCRIPTION
 Dermatomyositis occurs more commonly in female patients.
 There are 2 types of DM: adult onset type & juvenile type.
 It presents as a proximal symmetrical muscle weakness with vasculitis affecting the
skin, muscles and internal organs.
 Patients find it hard to raise their arms to comb their hair or walk up the stairs due
to the proximal muscle weakness.
 It can be severe enough to affect the muscles needed for speech and swallowing
and is also known to cause respiratory compromise.

5. EPIDEMIOLOGY
 The estimated incidence of dermatomyositis is 9.63 cases per million
population.
 The estimated incidence of AMD is 2.08 cases per million.
 Dermatomyositis can occur in people of any age. Two peak ages of onset
exist: in adults, the peak age of onset is approximately 50 years, whereas
in children, the peak age is approximately 5-10 years.
 Dermatomyositis and polymyositis are twice as common in women as in
men. Neither condition shows any racial predilection

6. CAUSE
 The cause of dermatomyositis is unknown. However, genetic, immunologic,
infectious, and environmental factors have been implicated.
Infectious agents have been suggested as possible triggers of dermatomyositis.
These include the following:
1. Viruses (eg, coxsackievirus, parvovirus, echovirus, human T-cell lymphotropic
virus type 1 [HTLV-1], HIV)
2. Toxoplasma species
3. Borrelia species

7. CAUSE
 Cases of drug-induced dermatomyositis have been reported.
Dermatomyositis-like skin changes have been reported with
hydroxyurea in patients with chronic myelogenous leukemia or essential
thrombocytosis.

8. AGENTSTHAT MAYTRIGGERTHE
DISEASE
 Statins
 Penicillamine
 Anti–tumor necrosis factor drugs
 Anti–programmed cell death drugs [28]
 Interferon
 Cyclophosphamide
 Bacillus Calmette-Guérin (BCG) vaccine
 Quinidine

9. IMMUNOPATHOGENESIS
 DM is an immune-mediated disorder, with proven immunohistopathology and
response to immunosuppression.
 The typical histopathologic findings of DM in muscle include perifascicular
atrophy, endothelial cell swelling, vessel wall membrane attack complex (MAC)
deposition, capillary necrosis, infarcts, major histocompatibility complex (MHC)
I upregulation, and the presence of an inflammatory infiltrate consisting of T
and B lymphocytes, macrophages, and plasma cells.

10. IMMUNOPATHOGENESIS
 There are findings of predominant perimysial and perivascular B/CD4+ T cell infiltrate
and intravascular MAC deposition.
 Recent studies have provided evidence that 30–90% of the CD4+ cells found in DM
muscle are actually plasma cytoid dendritic cells.
 The typical histopathologic findings in DM skin include epidermal basal cell vacuolar
degeneration, apoptosis of epidermal basal and suprabasal cells often with epidermal
atrophy, and increased dermal mucin deposition.
 Features that are more specific to DM over cutaneous lupus include C5b-deposition in
both dermal vasculature and the dermal-epidermal junction and a perivascular
lymphocytic infiltrate.

11. IMMUNOPATHOGENESIS
 DM has traditionally been viewed as a humorally mediated vasculopathic disease
given the findings of autoantibodies and complement deposition in vessels.
 The proposed mechanism has been that binding of antibodies targeting the
endothelium of the endomysial capillaries leads to activation of the complement
system with subsequent MAC deposition.
 This in turn may lead to endothelial swelling, capillary necrosis, perivascular
inflammation, and muscle ischemia.
 Relative hypoperfusion of the perifascicular regions is thought to explain the
findings of atrophy in this region on muscle biopsy.

12. CLINICAL MANIFESTATIONS
Muscle disease
Skin disease
Lung disease

13. MUSCLE DISEASE
 DM presents with a varying degree of muscle weakness that is insidious in
onset and gradually worsens over weeks to months, but a more fulminant
progression can occur.
 The initial presentation of muscle involvement is typically symmetric and
proximal, with distal muscle weakness occurring late in the course of the
disease.
 Patients often have difficulty with activities such as rising from a chair, climbing
stairs, lifting objects, or washing their hair.

14. MUSCLE DISEASE
 Difficulty holding and manipulating objects can occur with distal muscle
involvement.
 When the neck extensor muscles are involved, patients can present with
head drop. With more severe disease, patients can develop dysphagia,
dysphonia, and weakness in the muscles of respiration.
 Myalgias and muscle tenderness are less common but can occur in up to
30% of patients.

15. SKIN DISEASE
 The characteristic rash of DM can occur before, shortly after, or
at the same time as muscle weakness.
 A hallmark sign of DM are Gottron's papules

16. GOTTRON’S PAPULES
 These lesions primarily consist of erythematous
to violaceous papules and plaques over the
extensor surfaces of the metacarpophalangeal
and interphalangeal joints.
 These lesions may have accompanying scale, and
can sometimes develop ulcerations; active
lesions tend to resolve with dyspigmentation,
atrophy, and scarring.
• Gottron's sign refers to erythematous macules and patches overlying the elbows and/or
knees, and are less specific findings for DM

17. SKIN DISEASE
 Another hallmark sign of DM is the heliotrope
rash which consists of violaceous erythema of
the upper eyelids often with associated edema
and telangiectasia.
 It should be noted that in darker skin types, this
erythema may be subtle and overlooked.
 Erythematous patches and/or plaques in other
characteristic sun-exposed or nonsun-exposed
areas may also be seen in DM.

18. HELIOTROPE RASH
 A confluent erythema in the malar distribution
involving the cheeks and extending over the nasal
bridge may be seen, and can often involve the
nasolabial folds.
 More extensive involvement can be seen in other
areas including the forehead, lateral face, and
ears.
 Confluent macular erythema over the lower
anterior neck and upper anterior chest can also be
seen (the so-called “V” sign)

19. SKIN DISEASE
 A shawl sign refers to erythema over the upper back, posterior neck,
and shoulders, sometimes with extension to the lateral arms (figure d)
 Nonsun-exposed areas can also be involved, especially the sclap, lower
back, and lateral thighs (Holster sign). (figure e)

20. VASCULOPATHIC LESIONS
 Vasculopathic lesions of DM include livedo reticularis, ulceration, and
telangiectasia (including gingival and periungual).
 On nailfold capillary examination, DM patients can have prominent
dilated and tortuous blood vessels accompanied by avascular areas.
 The degree of telangiectasias and vessel drop-out reflects ongoing
disease activity, particularly in the skin.

21. VASCULOPATHIC LESIONS
(a) Shallow, crusted erosions arising in an area of intense inflammation.
(b) Telangiectatic macules and papules on the breast in a patient with longstanding disease

22. HAND LESIONS
 Rough and cracked, hyperkeratotic, “dirty” horizontal lines on the lateral
and palmer areas of the fingers, resembling “mechanics” hands.
 Cuticular overgrowth and irregularity on the nail plate.
 Palmar and plantar erythema occasionally associated with a mottled
appearance may be indicative of vascular instability in DM patients.
 In addition, raised, often tender papules or plaques can be present
overlying joint creases of the palmar hands.
 On biopsy, these lesions demonstrate mucin deposition in the dermis.

23. HAND LESIONS
(a) Mechanic hands: Erythematous, scaling papules located on the lateral aspect of
the second and third digits.
(b) Overgrown cuticles are seen containing multiple hemorrhages.

24. OTHER CUTANEOUS FEATURES
 Other potentially significant cutaneous features of DM include panniculitis,
alopecia (focal, due to areas of inflammation on the scalp, or diffuse), and
flagellate erythema (linear streaks in the upper back occurring in association with
excoriations from pruritus).
 Poikiloderma is a manifestation of disease chronicity with a mottled pattern of
hyperpigmented and hypopigmented macules interspersed with telangiectasias.
 Lastly, calcinosis involving the skin, subcutaneous tissue, fascia, or muscle seen in
areas of potential trauma or inflammation is often a late complication, seen more
often in juvenile than in adult cases.

25. LUNG DISEASE
 ILD is a significant source of morbidity and mortality in patients with
inflammatory myositis.
 It has been estimated that about 35–40% of patients with either polymyositis or
dermatomyositis will suffer from ILD during the course of their illness.
 Large case series have suggested that over 75% of patients who have an anti-
synthetase antibody will develop ILD, however, a small prospective longitudinal
study suggested that anti-Jo antibody positivity may portend a better ILD
prognosis.

26. INERSTITIAL LUNG DISEASE(ILD)
 Pulmonary function testing typically reveals a restrictive disease pattern (forced
vital capacity [FVC] or total lung capacity [TLC] <80% predicted for age) or a
decrease in diffusing capacity of carbon monoxide (DLCO).
 High-resolution CT (HRCT) scanning is very sensitive for the
detection of ILD and can be helpful to follow disease progression. Characteristic
features on HRCT include nodules, linear opacities, fibrosis with or without
honeycombing, consolidation, traction bronchiectasis, and bronchiolectasis
 Bronchoscopy with bronchoalveolar lavage is helpful to rule out occult infections
in patients who are chronically immunosuppressed.

27. OESOPHAGEAL INVOLVEMENT
 Esophageal disease in DM patients most commonly presents with
dysphagia to solids and liquids due to loss of pharyngo–esophageal
muscle tone.
 Other signs of pharyngo–esophageal involvement include nasal
speech, hoarseness, nasal regurgitation, and aspiration pneumonia.
 A diagnosis can be confirmed by manometry with low amplitude/absent
pharyngeal contractions and decreased upper esophageal sphincter
pressures

28. SYSTEMIC MANIFESTATIONS
 General systemic disturbances, fever, arthralgia, malaise, weight loss, Raynaud phenomenon
 Dysphagia due to esophageal skeletal muscle involvement
 Gastroesophageal reflux due to esophageal smooth muscle involvement
 Dysphonia
 Atrioventricular defects, tachyarrhythmias, dilated cardiomyopathies
 Gastrointestinal ulcers and infections, more common in children
 Pulmonary involvement due to weakness of thoracic muscles, interstitial lung disease
 Subcutaneous calcification, which may result in contracture of joints; more common in children
 Children may also develop a tiptoe gait secondary to flexion contracture of the ankles in early childhood
 Malignancy in adult patients

29. LABORATORYTESTING
 Muscle enzyme levels
 Myositis-specific antibodies, Antinuclear antibody levels
 Pulmonary function studies with diffusion capacity
 Electrocardiography, Esophageal manometry
 Colonoscopy to screen for underlying malignancy
 Papanicolaou smear in women for malignancy screening
 CA-125 and CA-19-9 for malignancy screening

30. DIAGNOSIS
 In classic DM, in addition to cutaneous manifestations and proximal muscle
weakness, patients have abnormal muscle enzymes (creatine kinase [CK],
aldolase, aspartate aminotransferase [AST], alanine aminotransferase [ALT], and/or
lactate dehydrogenase [LDH]).
 Electromyogram (EMG) studies are useful early in disease and show abnormal
findings in 70–90% of cases but are nonspecific and can be seen in other muscle
diseases.

31. DIAGNOSIS
 Typical EMG findings include increased spontaneous and insertional activity with
fibrillation potentials, positive sharp waves, complex repetitive discharges, early
recruitment, and small polyphasic motor until potentials.
 Imaging with magnetic resonance imaging (MRI) is a sensitive technique for
evaluation of myositis with the presence of muscle edema.
 Areas of inflammation are hyperintense on T2-weighted images with clearer
images seen with fat suppression or short tau inversion recovery sequences

32. DIAGNOSIS
 Muscle and/or skin biopsies are required to make a definite diagnosis and to rule
out other disease mimickers.
 The muscle biopsy should be obtained from moderately weak muscle areas as
assessed by physical exam, areas of inflammation located by MRI, or muscles
contralateral to those identified as abnormal on EMG.

33. BOHAN AND PETER’S CRITERIA

34. DALAKAS AND HOHLFELD’S
CRITERIA

36. BIOMARKERS
Targets, prevalence, and clinical association of myositis-specific antibodies. ILD: interstitial lung disease;TIF:
transcription intermediary factor; RNA: ribonucleic acid; MDA: melanoma differentiation-associated gene; CADM:
clinical amyopathic dermatomyositis; NXP: nuclear matrix protein; SAE: small ubiquitin-like modifier-activating
enzyme;ARS: aminoacyl tRNA synthetase.

37. DIFFERENTIAL DIAGNOSIS
 Discoid Lupus Erythematosus
 GraftVersus Host Disease
 Lichen Myxedematosus
 Lichen Planus
 Multicentric Reticulohistiocytosis
 Parapsoriasis
 Pityriasis Rubra Pilaris
 Polymorphous Light Eruption
 Psoriasis
 Rosacea
 Sarcoidosis
 Subacute Cutaneous Lupus
Erythematosus (SCLE)
 Systemic Lupus Erythematosus (SLE)
 Tinea Corporis

38. PROGNOSIS
 Dermatomyositis may spontaneously remit in as many as 20% of affected
patients.
 About 5% of patients have a fulminant progressive course with eventual death.
 However, patients who survive the disease may experience residual weakness
and disability.
 Children with severe dermatomyositis may develop contractures.
 Therefore, many patients require long-term therapy.

39. PROGNOSIS
 Risk factors for a poorer prognosis in patients with dermatomyositis include the
following:
 An associated malignancy
 Cardiac, pulmonary, or esophageal involvement
 Older age (ie, >60 years)
 Dermatomyositis may cause death because of muscle weakness or
cardiopulmonary involvement.
 Patients with an associated cancer may die of the malignancy.

40. PROGNOSIS
 The association between malignancy and dermatomyositis has long
been recognized.
 An estimated 25% of patients with dermatomyositis have or will develop
an associated malignancy, and the risk appears to remain elevated for 3-
5 years.

41. TREATMENT
Therapy for the muscle component of dermatomyositis involves the use of corticosteroids,
typically with an immunosuppressive agent.
Therapy for the skin disease includes the following, among other options:
 Sun avoidance, Sunscreens and photoprotective clothing
 Topical corticosteroids
 Antimalarial agents
 Methotrexate
 Mycophenolate mofetil
 Immune globulins

42. TREATMENT OF MUSCLE
DISEASE
 The mainstay of therapy for the muscle disease is systemically
administered corticosteroids.
 Traditionally, prednisone (0.5-2 mg/kg/d) up to a dose of 60 mg/d is
given as initial therapy.
 The drug should be slowly tapered to avoid relapse of the disease.
Because most patients develop steroid-related toxic effects, most
authorities administer a steroid-sparing immunosuppressive or cytotoxic
agent early in the course

43. TREATMENT OF MUSCLE
DISEASE
Drugs reported to be steroid-sparing in some patients or in small open-label studies have included the
following
 Methotrexate
 Azathioprine
 Cyclophosphamide
 Cyclosporine
 Mycophenolate mofetil
 Leflunomide
 Chlorambucil
 Tacrolimus

44. TREATMENT OF MUSCLE
DISEASE
 Generally, methotrexate, mycophenolate mofetil, or azathioprine are
used first line as glucocorticoid-sparing agents for muscle involvement.
 Response rates to methotrexate have been reported to be approximately
70-80%.
 In addition, one small, randomized trial supported the long-term benefits
of azathioprine as compared with prednisone monotherapy.
 Results with cyclophosphamide in severe cases have been disappointing.

45. TREATMENT OF MUSCLE
DISEASE
 For refractory cases, the use of monthly high-dose intravenous immune
globulin (IVIG) for 6 months has proved beneficial in the short term.
 In addition to its positive effects on refractory muscle and skin disease,
IVIG has been reported to be beneficial for other systemic manifestations,
including severe esophageal dysfunction.

46. TREATMENT OF MUSCLE
DISEASE
 The calcineurin inhibitor tacrolimus appears to be effective, safe, and well
tolerated in patients with dermatomyositis that is refractory to other
treatments.
 In addition to improvement in muscle strength and physical function,
amelioration of skin lesions and interstitial lung disease have been
reported.
 However, randomized, controlled trials have yet to be conducted

47. TREATMENT OF SKIN DISEASE
 Therapy of cutaneous disease of dermatomyositis is often difficult
 First-line therapy is to recognize that the patient is photosensitive and to
prescribe sun avoidance and sun protection measures, including broad-
spectrum sunscreens and photoprotective clothing.
 The cutaneous component of dermatomyositis is exacerbated by sunlight
and other sources of ultraviolet light; in addition, the muscle component
may be exacerbated.

48. TREATMENT OF SKIN DISEASE
 Hydroxychloroquine and chloroquine have been beneficial in small, open-
label case studies; however, roughly 25-30% of patients with
dermatomyositis who are treated with hydroxychloroquine develop a
drug eruption, and patients should be counseled regarding this potential
side effect.
 Some patients who develop a drug eruption to hydroxychoroquine may
go on to tolerate chloroquine

49. TREATMENT OF SKIN DISEASE
 Methotrexate is often considered first-line systemic therapy if
antimalarials fail or are contraindicated.
 Mycophenolate mofetil has been reported to be useful as well.
 Azathioprine has been reported to be effective for muscle involvement,
but
 Azathioprine appears to be less effective for cutaneous disease. Sirolimus,
tactrolimus, and dapsone inhibitors are among other immunomodulatory
medications that may be of value in some patients.

50. TREATMENT OF SKIN DISEASE
 Intravenous immune globulin (IVIG) has benefited muscle involvement and
cleared the skin lesions in the patients in whom it was used.
 A study found that muscular and cutaneous involvement were significantly
improved at 6 months in the IVIG-treated group, and modified Cutaneous
Dermatomyositis Area and Severity Index (CDASI) scores were significantly
improved over pretreatment scores during 4 years of follow-up
 Subcutaneous IgG has also been effective in dermatomyositis.
 Rituximab has been used for skin disease, but the results are mixed.

51. GUIDELINES RECOMMENDATION

52. EMERGINGTHERAPEUTIC
OPTIONS

53. REFERENCES
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https://doi.org/10.1155/2019/9141420
3. Dalakas MC and Hohlfeld R, Lancet 362:971-82, 2003
4. Bohan A and Peter JB, N Engl J Med. 292:344-7, 1975; Bohan A and Peter JB, N Engl J Med. 292:403-7,
1975
5. Hautarzt. 2015 Aug;66(8):604-10.
6. Current Rheumatology Reports (2019) 21:53 https://doi.org/10.1007/s11926-019-0850-9
7. Medscape dermatomyositis