What Causes dermtomyositis?

NEET SS
#1

Dermatomyositis is usually associated with?

  • A. Rheumatoid arthritis
  • B. SLE
  • C. Systemic sclerosis
  • D. Underlying Malignancy
  • E. Polymyalgia Rheumatica

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Answer: D

Description : Dermatomyositis is usually associated with an underlying malignanacy in 25% of patients Source

Study Notes:

What Is Dermatomyositis?

Dermatomyositis:

It is a non-infectious inflammatory disorder of the skin and skeletal muscle. It is characterized by immune-complex deposition in blood vessels with Complement activation causing skeletal muscle inflammation and skin involvement.

What Causes dermtomyositis?

The cause is unknown but dermatomyositis is caused by an autoimmune disorder. The main target of antibodies are small blood vessels (capillaries)

What are the Clinical findings?

The most common sign and symptoms of dermatomyosistis involves Skin changes and muscle weakness.

Symptoms includes:

  • Bilateral symmetrical proximal muscle weakness:
    • Difficulty climbing stairs; arising from chairs, and brushing hair with or without tenderness of the affected area
  • Fever, weight loss and fatigue.
  • Grotton’s papules : (Pathognomonic skin finding)
    • Violaceous, scaly patches symmetrically over knuckles, elbows, and Knees.
  • Heliotrope Eyelids (purple-red eyelid discolouration with periorbital edema)
  • Shawl Sign (erythema of face, neck, shoulders, upper chest, and back

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Organ Involvement:

Dermatomyositis may involve:

  • Esophageal muscles causing Dysphagia.
  • Lungs = Interstitial lung disease.
  • Blood vessels = Vasculitis.
  • Heart = Myocarditis

Association with Malignancy?

It is associated with three-fold increased risk of malignancy.

Common sites are:

  • Ovarian-most common
  • Lung
  • Gastrointestinal Lymphoma

Diagnostic Tests:

1. Muscle Enzymes:

  • Cretinine kinase(Ck): Elevated
  • Aldolase: elevated

2. Antibodies:

  • Anti-neutrophilic antibody (ANA): Positive
  • Anti-synthetase antibody( anti-jo-1): Positive
    • Especially in a patient with interstitial lung disease

3. Chest Xray: For lung involvement

4. Other Procedures:

  1. Muscle biopsy: Most accurate investigation for dermatomyositis

  2. Skin biopsy .

  3. Electromyograpgy

  4. Patient should also be tested for malignancies.

How dermatomyositis is treated?

  • Drug of choice : Steroids – (the mainstay of treatment)
  • When unresponsive to steroids:
    • Methotrexate
    • Azathioprine
    • Intravenous immunoglobulin
    • Mycophenolate.

Complications:

  • Lungs: Respiratory failure due to the weakness of thoracic muscle
  • Cardiovascular : Myocarditis, congestive heart failure and arrhythmias may develop
  • Esophagus: Esophageal disorder (difficulty in swallowing)
  • Calcium deposition: Calcium deposition may occur in skin, muscles and tissues

Differentials

  1. Inflammatory myopathies:
  • Polymyositis
  • Inclusion body myositis

  1. Polymyalgia rheumatica

  2. Fibromyalgia