DERMATOMYOSTIS-CAUSES,PATHOGENESIS,CLINICAL FEATURES,ANTIBODIES,SKIN SIGNS,DIFFERENCE WITH OTHER INFLAMMATORY MYOSITIS

1. INFLAMMATORY MYOPATHIES
PART -1 DERMATOMYOSITIS

2. INTRODUCTION:
 Largest group of acquired and potentially treatable
myopathies in children and adults.
- Primary causes include-dermatomyositis,polymyositis,inclusion body
myositis
Commonly immune mediated and some are associated
 With SLE,Systemic sclerosis,sarcoidosis.
 symptoms of muscle weakness, fatigue &
inflammation are commonly seen

3. Causes
INFECTIOUSBACTERIAL,VIRAL, PARASITIC and FUNGAL
IDIOPATHIC/primary
1. POLYMYOSITIS
2. DERMATOMYOSITIS
3. INCLUSION BODY MYOSITIS

4. COLLAGEN DISEASE ASSOCIATED
1. LUPUS ERYTHEMATOUS
2. RHEUMTOID DISEASE
3. SJOGREN S SYNDROME
4. POLYARTERITIS
DRUG INDUCED

5. PATHOGENESIS
• Immunologic disease-d/t damage to small blood vessels-
muscle injury.
• Humoral immune mechanisms
• Immune complex deposition in endothelium of capillaries of
myofibers
• Complement component deposition in vessel wall

6. • MAC formation
• Perivascular inflammation
• Decrease in number of intramuscular blood vessels
• Hypoxia of muscle-Perifascicular atrophy as these
fibers.

7. • AUTOANTIBODIES
1. Anti-Mi2 ab-against a helicase implicated in nucleosome
remodeling- GOTTRON PAPULES & HELIOTROPE RASH.
2. Anti –jo ab-against the enzyme histidyl t-RNA synthetase-
Interstitial lung disease, non-erosive arthritis, mechanics
hands.
3. Anti-P155/P140 ab-against several transcriptional regulators-
paraneoplastic & juvenile dermatomyositis.
 Direct link between these autoantibodies & disease pathogenesis is not yet
established.

9. CLINICAL FEATURES
 M/C-Females.
 4th to 6th decade.
 Muscle weakness –slow in onset, symmetric
 Myalgias
 Proximal muscles affected first- getting up from chair &
climbing steps is difficult..
 Distal muscles controlling fine movements are affected late .
DERMATOLOGIC MANIFESTATIONS:
 Precedes muscle weakness.

10.  HELIOTROPE RASH- Periorbital violaceous erythema with or
without edema of eyelids & periorbital tissue.
Highly characteristic.
 GOOTRON PAPULES- scaly erythematous eruption or dusky red
Patches over the knuckles ,elbow & knees.
 V-sign- macular violaceous erythema over V –shaped region
of neck & upper chest.
 SHAWL-sign- macular violaceous erythema over nape, back &
shoulders. May show photosensitivity.
 NAIL FOLD TELENGECTASIA- occurs in 30 to 60% early in
disease.

11.  Mechanics hands- hyperkeratosis, scaling, & horizontal
fissuring of the palms & fingers bilaterally.
 DYSPHAGIA-one third of cases.
 INTERSTITIAL LUNG DISEASE- rapidly progressive & sometimes
lead to death-in 30% cases.
 CARDIAC INVOLVEMENT– is common but cardiac failure rare.
 15% to 24% patients have associated malignancy .
 Dermatomyositis is viewed as paraneoplastic disorder.

13. Gotron papules

15. Nail fold telengectasia

16. JUVENILE DERMATOMYOSITIS
 C/F similar to DM with following differences:
 Age of onset-7 years.
 Less incidence of malignancy , ILD, cardiac involvement &
Myositis
 Specific antibodies.
 Lipodystrophy & calcinosis.
 Increased risk of vasculopathy-git peripheral nerves
 Prognosis is better in children than in adults.

17.  Some cases have no rash or an unrecognized rash
in darker skinned individuals (dermatomyositis sine
dermatitis)
 Some cases lack muscle involvement
(dermatomyositis sine myositis or amyopathic
myositis)
 CK LEVELS- increased upto 50 times UNL in 90%
pts, while in others its normal.

21. DIAGNOSIS
 Direct IF- shows deposits of IgG , IgM & C3 in intramuscular
blood vessels-in most children & adult cases.
 C5-9 complement components or MAC are also seen.
 EM shows granular appearance of immune complexes deposits-
in perimysial venules & arterioles.
 B lymphocytes & CD4 infiltrate around blood vessels.

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