This document discusses muscle weakness and skin rash (dermatomyositis). It provides information on the clinical presentation, causes, diagnostic criteria and classification, investigations, histopathological findings, treatment and prognosis of dermatomyositis. Key points include that dermatomyositis involves proximal muscle weakness and a skin rash. Diagnosis involves elevated muscle enzymes, electromyography, muscle biopsy and the presence of a skin rash. Treatment primarily involves oral steroids. Prognosis depends on factors like age, presence of malignancy and disease recalcitrance.
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Muscle weakness & rash (Dermatomyositis)
1. MUSCLE WEAKNESS & SKIN RASH
( DERMATOMYOSITIS )
Dr. Mohammad Tanvir Islam
Assistant Professor , Dept of Medicine
Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh
2. IS THIS A CASE OF MYOPATHY??
Proximal muscle weakness evident by-
Difficulty in standing from sitting position,
combing hair etc.
Normal tendon reflexes
Pain & tenderness often present
3. WHAT MAY BE THE CAUSE OF THIS MYOPATHY
Inflammatory myopathy
Drug induced
Endocrine
Infection
Alcohol
4. MYOPATHY WITH SKIN RASH
Dermatomyositis
Steroid induced myopathy
Hypothyroidism
Other CTDs
5. DERMATOMYOSITIS
Double peak of onset
Average age of onset is 40
In 40% individuals the skin disease is the sole
manifestation at onset
Muscle disease may occur-
Concurrently,
Precede the skin disease, or
Follow the skin disease by weeks to years.
10. Rash in Shawl distribution
SKIN RASH OF DERMATOMYOSITIS
11. COMPLICATIONS
Dermatomyositis & malignancy
6-7 fold increase risk of malignacy
Usually early within 3 years of diagnosis
chances decreases thereafter
Highest in patients diagnosed after 45yrs of
age
Ovarian and gastric cancer and lymphoma
are most common
13. CLASSIFICATION CRITERIA FOR POLYMYOSITIS
AND DERMATOMYOSITIS*
1. Skin lesions
Heliotrope: red-purple edematous erythema on the upper palpebra
Gottron’s sign: red-purple keratotic, atrophic erythema or macules on the
extensor surface of finger joints
Erythema on the extensor surface of extremity joints, slight raised red-purple
erythema over elbows or knees
2. Proximal muscle weakness (upper or lower extremity and trunk)
3. Elevated serum creatine kinase or aldolase level
4. Muscle pain on grasping or spontaneous pain
5. Myogenic changes on electromyography (short-duration, polyphasic motor
unit potentials with spontaneous fibrillation potentials)
6. Positive anti-Jo-1 antibody test (histidyl-tRNA synthetase)
7. Nondestructive arthritis or arthralgias
8. Systemic inflammatory signs (temperature: more than 37°C [98.6°F] at axilla,
elevated serum C-reactive protein level or accelerated erythrocyte
sedimentation rate of more than 20 mm per hour by Westergren)
9. Pathologic findings compatible with inflammatory myositis (inflammatory
infiltration of skeletal evidence of active regeneration may be seen)
14. CLINICAL CRITERIA
1975, Bohan and Pete
Set of 5 criteria to aid in the diagnosis and
classification of dermatomyositis
and polymyositis
1. progressive proximal symmetrical weakness,
2. elevated levels of muscle enzymes,
3. an abnormal finding on electromyography,
4. an abnormal finding on muscle biopsy
5. Cutaneous disease.
15. SUBSETS OF MYOSITIS
Bohan and Peter suggested 5 subsets of myositis, as
follows :
Dermatomyositis
Polymyositis
Myositis with malignancy
Childhood dermatomyositis/polymyositis
Myositis overlapping with another collagen-vascular
disorder
Others-
postmyopathic dermatomyositis
amyopathic dermatomyositis [ADM], or dermatomyositis
sine myositis
16. HOW WILL YOU INVESTIGATE
Enzymes –
CK
Aldolase
LDH
carbonic anhydrase isoenzyme III
17. ANTIBODIES
ANA commonly positive (60-80%)
Anti –Mi-2 highly specific but sensitivity only
25%
Anti-Jo-1 more in polymyositis,associated
with ILD,raynauds and arthritis (positive in
20%)
autoantibody against p155 highly associated
with cancer
18. IMAGING
MRI- useful in diagnosing inflammatory
myopathy(even in patients without weakness), it
also helps in taking muscle biopsy in choosing
proper site
EMG- helps to differentiate from neuropathy and
choosing biopsy site.
CXR
Barium swallow
USG
CT scan
19. HISTOPATHOLOGICAL FINDINGS
Findings on muscle biopsy can be
diagnostic.
Perivascular and interfascicular
inflammatory infiltrates with adjoining groups
of muscle fiber degeneration/regeneration
This contrasts with polymyositis infiltrates,
which are mainly intrafascicular
(endomysial inflammation) with scattered
individual muscle fiber necrosis.
20. Figure 2
A, B: Depletion of capillaries
in dermatomyositis (A) with
dilatation of the lumen of the
remaining capillaries,
compared with a normal
muscle (B). C: Perifascular
atrophy in dermatomyositis.
D: Endomysial inflammation
in polymyositis and inclusion-
body myositis with
lymphocytic cells invading
healthy fibres. E: The MHC-
I/CD8 complex in polymyositis
and inclusion-body myositis.
HISTOPATHOLOGICAL FINDINGS OF DERMATOMYOSITIS & POLY MYOSITIS
Source: The Lancet 2003; 362:971-982 (DOI:10.1016/S0140-6736(03)14368-1)
Terms and Conditions
21. TREATMENT
Oral prednisolone is the mainstay of treatment
0.5-1.5 mg/kg starting dose.given untill CK level
is normal , then tapered slowly over 12 month
period
Prednisolone itself worsen myopathy in some
cases and steroid induced myopathy is
differentiated by sparing the neck flexor
strength
22. TREATMENT
Other drugs used- methotrexate,azathiprine,
cyclophosphamide, cyclosporine
IV immunoglobulin for refractory cases
Physiotherapy
24. PROGNOSIS
Spontaneous remission in 20%
5% have fulminant progression and eventual
death
Poor prognostic factor-recalcitrant disease,
delay in diagnosis, older age, malignancy,
fever, asthenia-anorexia, pulmonary
interstitial fibrosis, dysphagia and
leukocytosis.
Cause of death-Malignancy, cardiac and
pulmonary dysfunction, and infection