Muscle weakness DDx

Muscle weakness – Differential Diagnosis

Common causes

• Injury (including overuse)
• Viral infections
• Joint pains
• Disuse atrophy
• Vitamin D deficiency
• Peripheral nerve lesions
• Hypothyroidism
• Fibromyalgia
• Chronic fatigue syndrome
• Psychogenic

Must Not Miss

• Statins(inc Rhabdomyolysis)
• Polymyalgia rheumatica
• Malignancy
• Peripheral vascular disease
• Guillain-Barré syndrome

Easily missed

• Connective tissue diseases
• Polymyositis
• Peripheral polyneuropathy
  • Diabetic neuropathy
  • Alcohol
  • Vitamin B12 deficiency
  • Metabolic
  • Connective tissue diseases
  • Heavy metals
  • Paraneoplastic syndrome
  • Idiopathic & others

Red flags

• Cold pulseless limb
• Progressive symptoms
• Systemic symptoms (fever, weight loss)

Investigations to consider

• FBC, CRP/ESR
• U&Es, LFTs, TFTs, Bone profile
• Serum glucose, CK, B12 + Folate
• Vitamin D
• Local X-ray
• EMG
• Nerve conduction studies
• Muscle biopsies
• Lumbar puncture
• Angiography