Muscle Weakness Causes

Aka: Muscle Weakness Causes, Generalized Muscle Weakness Causes, Myopathy Causes, Polymyositis Differential Diagnosis, Dermatomyositis Differential Diagnosis

1. See Also
   1. Polymyositis
   2. Dermatomyositis
   3. Muscle Weakness
   4. Muscle Weakness in Children
   5. Acute Motor Weakness Causes (Emergent Bilateral Motor Weakness)
   6. Acute Flaccid Paralysis
   7. Medication Causes of Myositis
   8. Unilateral Weakness
   9. Neuropathy
   10. Peripheral Neuropathy
   11. Symmetric Peripheral Neuropathy
   12. Asymmetric Peripheral Neuropathy
   13. Fatigue Causes
   14. Dyspnea Causes
   15. Arthralgia Causes
2. Differential Diagnosis: Cutaneous (Dermatomyositis)
   1. Dermatomyositis
   2. HIV Infection (once Immunodeficiency occurs)
   3. Lichen Planus
   4. Polymorphous light eruption
   5. Seborrheic Dermatitis
   6. Systemic Lupus Erythematosus
   7. Psoriasis
   8. Contact Dermatitis
   9. Atopic Dermatitis
   10. Trichinosis
   11. Alcohol
3. 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
4. Differential Diagnosis: Nerve Disorders
   1. Combined Upper Motor Neuron and Lower Motor Neuron
      1. Amyotrophic Lateral Sclerosis
   2. Upper Motor Neuron disorders
      1. CNS Lesion
      2. Spinal Cord Syndrome
      3. Multiple Sclerosis
      4. Cranial Dysraphism (e.g. Encephalocele)
      5. Spinal Dysraphism (e.g. Spina bifida)
   3. Lower Motor Neuron disorders
      1. Myasthenia Gravis
      2. Lambert-Eaton Syndrome
      3. Guillain-Barre (other autoimmune polyneuropathies)
      4. Neuropathy
         1. See Peripheral Neuropathy
         2. See Symmetric Peripheral Neuropathy
         3. See Asymmetric Peripheral Neuropathy
         4. Diabetic Neuropathy
         5. Peripheral Nerve Injury or Compression Neuropathy (e.g. Carpal Tunnel Syndrome, Lumbar Radiculopathy)
5. 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
6. Differential Diagnosis: Toxic Myopathy or Neuropathy
   1. See Medication Causes of Myositis
   2. Steroid Myopathy
   3. Acute Rhabdomyolysis
   4. Amyloidosis
   5. Porphyria
   6. Organophosphate Poisoning
   7. Botulism
   8. Substances of Abuse
      1. Alcoholic Myopathy or Neuropathy
      2. Volatile Inhalant Abuse (Toluene in glues)
      3. Cocaine
   9. Heavy Metal Poisoning
      1. Arsenic Poisoning
      2. Lead Poisoning
      3. Mercury Poisoning
      4. Thallium Poisoning (contained in rat poisons)
   10. Venoms
       1. Tick Paralysis
       2. Snake Envenomation
7. Differential Diagnosis: Infections
   1. Viral
      1. Influenza
      2. Epstein Barr Virus
      3. Coxsackievirus
      4. Rubella
      5. Human Immunodeficiency Virus (HIV)
      6. Polio
      7. Rabies
      8. West Nile Virus
      9. Dengue Fever
   2. Bacterial
      1. Staphylococcus
      2. Streptococcus
      3. Clostridium
      4. SalmonellaTyphus
      5. Mycobacterium leprae
      6. Lyme Disease
      7. Syphilis
   3. Parasitic
      1. Toxoplasmosis
      2. Trichinella
      3. Schistosomiasis
      4. Cysticercosis
8. Differential Diagnosis: Rheumatologic
   1. Polymyalgia Rheumatica
   2. Systemic Sclerosis
   3. Sarcoidosis
9. References
   1. Euwer (1994) Curr Opin Rheumatol 6:583-9 [PubMed]
   2. Koler (2001) Am Fam Physician 64(9):1565-72 [PubMed]
   3. Larson (2020) Am Fam Physician 101(2):95-108 [PubMed]
   4. Pachman (1995) Pediatr Clin North Am 42:1071-98 [PubMed]