2. INTRODUCTION
➢Dermatomyositis is a rare acquired immune-
mediated muscle disease characterized by muscle
weakness and skin rash.
➢It is classified as one of the idiopathic inflammatory
myopathies (IIM) with some clinical differences and
findings.
3. ➢Along with skin findings and symmetric proximal
skeletal muscle weakness, it affects other organ
systems such as pulmonary, cardiovascular, and
gastrointestinal systems.
➢Clinically amyopathic dermatomyositis (CADM) is
a condition in which patients have characteristic
cutaneous findings of dermatomyositis but do not
have muscle weakness.
4. ➢The condition can affect adults and children.
➢In children, it appears between 5 and 15 years of
age.
➢In adults, it occurs in the late 40s to early 60s.
➢Dermatomyositis affects more females than males
with an incidence ratio of 2 to 3:1
5. EPIDEMIOLOGY
➢The estimated prevalence of polymyositis and
dermatomyositis (PM/DM) is 5 to 22 per 100,000
persons. (May 2023)
➢The incidence is approximately 1.2 to 19 per million
persons at risk per year.
➢Black race to white race ratio of incidence is 3 to 4:1.
6. ETIOLOGY
➢It is a condition with an unknown etiology but has various factors
implicating it.
Dermatomyositis
Factors
Genetic
HLA antigens
Immunological
Autoantibodies
(myositis-
specific)
Environmental
Infections,
drugs,
radiation
7. GENETIC
FACTORS
➢Patients with particular HLA haplotypes are at higher
risk.
➢HLA-A*68 North American Whites
➢HLA-DRB1*0301 African Americans
➢HLA-DQA1*0104
➢HLA-DRB1*07
➢DQA1*05
➢DQB1*02
➢DRB1*03-DQA1*05-DQB1*02 haplotypes are
strongly associated with the development of interstitial
lung disease.
→
→
→
→
Han Chinese
UK
11. PATHOPHYSIOLOGY
➢Humoral-mediated attack directed against the muscle capillaries and the endothelium
of arterioles.
➢Activation of completer factor-3 (C3), which forms C3b and C4b, followed by the
formation of the neoantigen C3bNEO and the C5b-C9 membrane attack complex
(MAC)
➢The membrane attack complex deposits on vascular walls and causes inflammation.
➢Hypoxic injury to the muscle fibers ensues, leading to atrophy of muscle fibers,
particularly the fibers at the periphery that are the most remote and away from the
vascular supply.
➢Over time, the capillary density reduces, and muscle fibers start to undergo necrosis
and degeneration.
12. ➢ HISTOPATHOLOGY (muscle and skin)
➢ Perivascular and perimysial inflammatory infiltrate – B cells,
CD4+ T helper cells, macrophages
➢ Perifascicular atrophy – a hallmark feature
➢ Microangiopathy – immunoglobulin and complement deposits,
reduced capillary density, and endothelial hyperplasia
➢ Skin – increased lymphocytic infiltrate and mucin deposition in
the dermis
14. HISTORYAND PHYSICAL
EXAMINATION
➢Insidious or acute onset of the diseased with waxing and
waning course
➢History of Typical Muscular and Cutaneous Signs and
Symptoms
➢Exclude other causes of muscle weakness
➢Detailed review of systems
➢Possible underlying malignancy
15. ➢ MUSCULAR
➢ Gradually progressive symmetric proximal muscle weakness and
difficulty in carrying out activities such as climbing stairs, getting up from
a seated position, lifting objects, combing hair, and raising their head from
a pillow.
➢ Reduced muscle strength in deltoids, hip flexors, and neck flexors.
➢ Mild muscle tenderness
➢ Depressed Deep Tendon Reflexes and Muscle Atrophy in severe cases
➢ Distal muscle strength preserved
16.
17. ➢ CUTANEOUS
➢ Onset may precede or coincide with muscular symptoms
➢ Skin rashes, photosensitivity, changes in pigmentation, and pruritis
➢ Alopecia and nail changes are also seen
➢ Gottron papules - dorsal metacarpophalangeal and interphalangeal joints
may show the presence of overlying erythematous or violaceous papules
with or without scaling or ulceration.
➢ Heliotrope rash - characteristic skin finding of dermatomyositis and
presents with a violaceous, or an erythematous rash affecting the upper
eyelids with or without periorbital edema. This finding may not be
apparent in patients with dark skin patients.
18. ➢OTHER SKIN FINDINGS
➢Gottron sign: erythematous macules or patches over the elbows or knees
➢Facial erythema: erythema over the cheeks and nasal bridge involving
the nasolabial folds. The rash may extend up to the forehead and laterally
up to the ears.
➢Shawl sign: erythema over the posterior aspect of the neck, upper back,
and shoulders at times, extending to the upper arms.
➢V sign: ill-defined erythematous macules involving the anterior aspect of
the neck and the upper chest.
➢Poikiloderma: atrophic skin with changes in pigmentation and
telangiectasia in photo-exposed or non-exposed areas.
19. ➢Holster sign: poikiloderma involving the lateral aspects of the
thighs.
➢Mechanic's hands: hyperkeratotic, cracked horizontal lines on
the palmar and lateral aspects of the fingers.
➢Scalp involvement: diffuse poikiloderma, with scaling and
pruritis.
➢Calcinosis cutis: calcium deposits in the skin
21. ➢ JOINTS
➢ Polyarthritis or arthralgia of the small joints of the hands, may present
with joint pain or swelling.
➢ RESPIRATORY
➢ Exertional dyspnea, exercise intolerance, non-productive cough due to
underlying Interstitial Lung Disease. On Auscultation – B/L dry
crackles
➢ Reduced chest movement due to respiratory muscle weakness
22. ➢ ESOPHAGEAL
➢ Dysphagia – due to weakness of muscles of the oropharynx
and upper esophagus
➢ May have symptoms of gastroesophageal reflux
24. PETER/BOHAN(1975) CRITERIA
FOR DIAGNOSIS
1.Symmetric proximal muscle weakness
2.Elevated serum muscle enzymes
3.Myopathic changes in electromyography (EMG)
4.Characteristic muscle biopsy abnormalities
5.Typical rash of dermatomyositis
25. INVESTIGATIONS
➢Blood analysis-A blood test will give elevated levels of muscle
enzymes that can indicate muscle damage. It can also detect
autoantibodies associated with different symptoms of dermatomyositis
➢Chest X-ray-can check for signs of the type of lung damage that
sometimes occurs with dermatomyositis.
➢Investigations for Malignancy – CA-125, CA-19-9 screening
26. ➢ Electromyography - Needle EMG, changes in the pattern of
electrical activity can confirm a muscle disease.
➢ MRI - assesses inflammation over a large area of muscle.
➢ Skin or muscle biopsy -A skin sample can help confirm the
diagnosis of dermatomyositis. A muscle biopsy might reveal
inflammation in your muscles or other problems, such as
damage or infection.
28. ➢Antimalarial medications. For a persistent rash, antimalarial
medication, such as hydroxychloroquine
➢Sunscreens. Protecting skin from sun exposure by applying
sunscreen and wearing protective clothing and hats is important
for managing the rash of dermatomyositis.
29. ➢Physical therapy- exercises to help maintain and improve
strength and flexibility
➢Speech therapy-If swallowing muscles are affected, speech
therapy can help learn how to compensate for those changes.
➢Diet Management – chewing and swallowing can become
more difficult in later stages. For easy-to-eat foods and changes
in diet.
