II. Differential Diagnosis: Cutaneous (Dermatomyositis)

III. Differential Diagnosis: Muscular Disorders

  1. Myotonia (muscle stiffness)
  2. Spinal Muscular Atrophy
  3. Critical Illness Myopathy
  4. Myositis
    1. Polymyositis
    2. Inclusion body Myositis
    3. Necrotizing Myositis
  5. Muscular Dystrophy
    1. Becker Muscular Dystrophy
    2. Limb-Girdle Muscular Dystrophy
    3. Myotonic Dystrophy

V. Differential Diagnosis: Endocrine and Metabolic Disorders

  1. Electrolyte
    1. Hypokalemia (e.g. Hypokalemic Periodic Paralysis)
    2. Hypocalcemia
    3. Hypomagnesemia
  2. Thyroid and Paraythyroid Disorders
    1. Hypothyroidism
    2. Hyperthyroidism
    3. Hypoparathyroidism
    4. Hyperparathyroidism
  3. Adrenal Disorder
    1. Cushing's Syndrome
    2. Addison's Disease (Adrenal Insufficiency)
  4. Disorders of Energy Metabolism (e.g. Glycogen Storage Disease)
    1. McArdle's disease (Glycogen Phosphorylase Deficiency)
    2. Adult acid maltase deficiency
    3. Carnitine-palmitoyltransferase deficiency

VI. Differential Diagnosis: Toxic Myopathy or Neuropathy

VIII. Differential Diagnosis: Rheumatologic

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