Quick Diagnosis: Dermatomyositis
Jonathan M S Levy, MD Candidate 20121
Benjamin Barankin, MD, FRCPC is a Toronto dermatologist
1
Faculty of Medicine, University of Toronto
Corresponding author email address: jon.levy@utoronto.ca
MeSH Terms: Dermatomyositis
The Case
A 66 year old female of Caribbean descent presented with a 6 month history of a
pruritic rash of the scalp and chest. The skin lesions were exacerbated by exposure to
sunlight. Further questioning revealed nonspecific weakness resulting in difficulty in
climbing stairs and rising from a chair. She denied any constitutional symptoms and
there is no family history of autoimmune disease.
On examination, periorbital swelling and violaceous papules over the dorsal aspect of
the metacarpophalangeal and interphalangeal joints were noted (Figure 1). As well,
poikilidermatous skin changes (a variegated appearance of the skin with
telangiectasia) were visible on the upper back (Figure 2) and chest (Figure 3).
Bloodwork revealed an elevated creatine kinase (12 500) and a positive ANA (1:320).
Anti-Jo-1 antibodies are present, while anti-Mi-2 are negative. Complete blood count,
thyroid stimulating hormone, creatinine, and liver enzymes were all within normal
limits.
A skin biopsy was performed to help confirm the diagnosis.
What is the diagnosis?
Diagnosis: Dermatomyositis
Clinical Presentation
Dermatomyositis (DM) is an autoimmune idiopathic inflammatory myopathy with
characteristic cutaneous findings such as a heliotrope rash and Gottron papules, as
well as proximal muscle weakness. There is an increased risk of malignancy in
individuals over 55 years of age.1 Five criteria are used in establishing a diagnosis of
DM: progressive proximal symmetrical weakness, elevated muscle enzymes,
characteristic findings on electromyograms, on muscle biopsy, and compatible
cutaneous disease.2
DM is relatively rare with an incidence of 6 cases per million. Age of onset follows a
bimodal distribution with juvenile and adult (>40 years) peaks. Incidence is almost
twice as common in women as men.3 Dermatologists and rheumatologists, and less
commonly neurologists, are typically involved in the care of DM patients. Juvenile
DM is often associated with vasculitis and calcinosis; interstitial pneumonitis,
cardiomyopathy, and arthritis are particularly common in juvenile DM as well.
Meanwhile, adult-onset DM may be associated with an internal malignancy,
especially ovarian cancer in women.4 Malignancy evaluations are thus recommended
for any patient with DM. Examination for an occult malignancy in otherwise
asymptomatic patients should be age-specific, or directed by symptoms and/or
findings on physical examination or laboratory tests.5
The clinical spectrum ranges from amyopathic DM, with only cutaneous symptoms,
to polymyositis, which only involves muscle inflammation. Various histopathologic
features are compatible with DM, but are not pathognomonic; these include: flattening
of the epidermis, hydropic degeneration of basal cell layer, edema of upper dermis,
scattered inflammatory infiltrate, PAS-positive fibrinoid deposits at dermal-epidermal
junction and around upper dermal capillaries, and accumulation of acid
mucopolysaccharides in the dermis.6 Muscle inflammation is confirmed with a deep
muscle biopsy, usually of a weak or tender shoulder or pelvic girdle muscle, by a
surgeon. The biopsy histologically shows segmental necrosis within muscle fibres
with the presence of inflammatory cells including histiocytes, macrophages,
lymphocytes, and plasma cells.6
While the etiology of DM and autoimmune disease in general are unknown, several
factors may be involved, including certain HLA types, polymorphisms in tumour
necrosis factor, abnormal T-cell activity, circulating autoantibodies, certain viruses,
and medications.
The appearance of skin disease may precede myositis or vice versa; alternatively, both
may concurrently appear. Muscle involvement manifests as a progressive muscle
weakness affecting proximal and limb girdle muscles, with or without muscle
tenderness and atrophy. Patients often have difficulty rising from a sitting or supine
position without using arms, raising their arms above their head (e.g. to comb their
hair), and in climbing stairs. Involvement of intercostals muscles may result in
difficulty breathing. Infrequently, facial/bulbar, pharyngeal, and esophageal muscles
may be affected, resulting in dysphagia. Deep tendon reflexes remain intact. The
main, unique skin finding is a periorbital heliotrope (violaceous-purple) rash, often
accompanied with edema. This may extend to involve the scalp (with non-scarring
alopecia) resulting in burning and pruritus, as well as the entire face, upper chest and
arms.6 Papular dermatitis with violaceous erythema may present in the same areas.
Gottron papules (flat-topped, violaceous papules) may appear on the back of the neck
and shoulders, over the metacarpophalangeal and interphalangeal joints, and less often
the knees and elbows. Periungual erythema with telangiectasia may be noted. Longlasting lesions on exposed skin may evolve into poikiloderma, which often distributes
in a V-pattern over the upper chest and back and anterior neck (shawl sign). While
patients do not complain of photosensitivity, the outbreak of dermatomyositis is
photodistributed and photoexacerbated, with the exception of heliotrope rash.
Infrequent skin manifestations include vesiculobullous, erosive lesions, and an
exfoliative erythroderma.
Differential Diagnosis
The differential diagnosis of DM includes seborrheic dermatitis, lupus erythematosus,
mixed connective tissue disease, steroid myopathy, allergic contact dermatitis,
pityriasis rubra pilaris, polymorphous light eruption, and lichen planus. Gottron
papules affect the skin overlying the joints in DM, as opposed to lupus erythematosus
in which lesions occur in the interarticular region of the fingers, sparing the skin
overlying the joints.
Diagnosis
During the active acute phase muscle enzyme levels should be obtained, including
creatine phosphokinase, which is most specific for muscle disease. Other tests of
possible assistance include aldolase and lactate dehydrogenase. The autoantibodies
antinuclear antibody (ANA), anti-Mi-2, and anti-Jo-1 are important tests to help
confirm the diagnosis. Workup may also include electromyography and MRI of the
affected muscle. Diagnosis of DM may be confirmed by the combination of
characteristic skin signs, proximal muscle weakness, elevated serum muscle enzyme
levels, characteristic electromyographic changes, and diagnostic muscle biopsy.2
Electrocardiogram is useful in detecting an associated myocarditis, atrial or
ventricular irritability, and/or atrioventricular block. Chest x-ray is recommended to
recognize interstitial fibrosis.6 Reduced peristalsis, due to myositis, can be diagnosed
with an esophageal x-ray.
Prognosis
Prognosis of DM is guarded, but with treatment prognosis becomes relatively good,
with the exception of patients with underlying malignancy or pulmonary involvement.
Aggressive immunosuppressive treatment improves survival rate dramatically.
Mortality rates in children are below 10% with the early and aggressive use of
glucocorticoids,6 although there is significant morbidity in the subset of patients with
calcinosis cutis. The most common causes of death in DM are malignancy, infection,
cardiac or pulmonary disease. Dramatic improvement of DM often occurs as a result
of treatment of an associated neoplasm.
Treatment
Myositis is treated using prednisone with or without immunosuppressive agents. Skin
manifestations are managed by avoiding sun exposure and by using sunscreens,
topical corticosteroids or topical calcineurin inhibitors, antimalarial agents, and/or
methotrexate or mycophenolate mofetil. High-dose IV immunoglobulin therapy is
useful for patients with recalcitrant DM to achieve or maintain remissions.7
Rituximab, an anti-CD20 antibody specific in targeting B cells, has shown benefit,8
but more research is needed.
Back to the Case
The patient was diagnosed with dermatomyositis on clinical grounds coupled with
laboratory evidence and histopathology. In consultation with rheumatology, she was
started on a tapering dose of prednisone at 50mg orally once daily for 4 weeks. As
well, methotrexate 15mg orally once weekly and folic acid 5mg orally once daily
(except on day of methotrexate) was initiated for long-term immunosuppressive
control. Betamethasone valerate 0.1% cream was to be applied to affected skin areas
twice daily. Sun avoidance and sun protective measures, such as broad-spectrum
sunscreens, were encouraged. A CT scan of the abdomen and pelvis did not reveal
any signs of ovarian or other underlying malignancy. At 2 months follow-up, the skin
lesions were fading and by 6 months her subjective proximal muscle weakness had
significantly improved and her skin greatly improved with only post-inflammatory
hyperpigmentation remaining.
Acknowledgments
None
Conflicts of Interest
None
Supporting Information
N/A
References
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Figures and Figure Captions
Figure 1: Gottron Papules: Violaceous, flat-topped papules are seen over the dorsal
aspect of the metacarpophalangeal andinterphalangeal joints.
Figure 2: Shawl sign: Poikiloderma skin changes on the upper back
Figure 3: Poikiloderma distributed in a V-sign over the anterior neck.