Infection:
Viral infection (e.g. Influenza)
Bacterial infection
Spirochete infection (E.g. Dengue fever; Trichinella)
Drugs:
Statins
Bisphosphonates
Corticosteroids
Ciprofloxacin
Clofibrate
Colchicine
Chloroquine
Emetine
Aminocaproic acid
Zidovudine
Bretylium
Penicillamine
Drugs causing hypokalemia
Metabolic disorders:
Vitamin D deficiency
Mitochondrial myopathy
Scurvy
Osteomalacia
Fibromyalgia
Endocrine:
Hypothyroidism
Hyperthyroidism
Cushing’s syndrome
Adrenal insufficiency
Hyperparathyroidism
Polymyalgia rheumatica
Rhabdomyolysis
Myositis<unk> 
Dermatomyositis
Myositis (peds)
Systemic lupus erythematosus
Rheumatoid arthritis
Inclusion body myositis
Sarcoidosis
Scleroderma
Sjögren’s syndrome
Psychiatric (e.g. somatic manifestations of depression)
Domestic abuse
Crush injury
Lyme disease
Ehlers-Danlos syndrome(hypermobility syndrome)
HIV myopathy
Hypophosphatemia
Hypokalemia
Hypothermia
Prolonged immobility
Strenuous exercise (overuse) or heat stroke
Seizure
Severe volume contraction
Alcoholism
Muscular dystrophy
Duchenne
Becker
Limb-girdle
Facioscapulohumeral
Myotonic dystrophy
Myotonia congenita
Compartment syndrome; Muscle infarction
Neuropathic
Chronic fatigue syndrome
Vasculitis
Sarcocystosis
Spinal stenosis
Diabetic lumbosacral plexopathy
Viral infection (e.g. Influenza)
Bacterial infection
Spirochete infection (E.g. Dengue fever; Trichinella)
Statins
Bisphosphonates
Corticosteroids
Ciprofloxacin
Clofibrate
Colchicine
Chloroquine
Emetine
Aminocaproic acid
Zidovudine
Bretylium
Penicillamine
Drugs causing hypokalemia
Vitamin D deficiency
Mitochondrial myopathy
Scurvy
Osteomalacia
Hypothyroidism
Hyperthyroidism
Cushing’s syndrome
Adrenal insufficiency
Hyperparathyroidism<unk> 
Dermatomyositis
Myositis (peds)
Duchenne
Becker
Limb-girdle
Facioscapulohumeral
Myotonic dystrophy
Myotonia congenita
Neuromuscular weakness
Upper motor neuron:
CVA
Hemorrhagic stroke
Multiple sclerosis
Amyotrophic Lateral Sclerosis (ALS) (UMN & LMN)
Lower motor neuron:
Spinal and bulbar muscular atrophy (Kennedy's syndrome)
Spinal cord disease:
Infection (Epidural abscess)
Infarction/ischemia
Trauma (Spinal Cord Syndromes)
Inflammation (Transverse Myelitis)
Acute flaccid myelitis
Degenerative (Spinal muscular atrophy)
Tumor
Peripheral nerve disease:
Guillain-Barre syndrome
Toxins (Ciguatera)
Tick paralysis
Diabetic peripheral neuropathy
NMJ disease:
Myasthenia gravis crisis
Botulism
Organophosphate toxicity
Lambert-Eaton myasthenic syndrome
Muscle disease:
Rhabdomyolysis
Dermatomyositis<unk> 
Alcoholic myopathy
Non-neuromuscular weakness
Can't miss diagnoses:
ACS
Arrhythmia/Syncope
Severe infection/Sepsis
Hypoglycemia
Periodic paralysis (electrolyte disturbance, K, Mg, Ca)
Hypokalemic periodic paralysis
Thyrotoxic periodic paralysis
Respiratory failure
Emergent Diagnoses:
Symptomatic Anemia
Severe dehydration
Hypothyroidism
Polypharmacy
Malignancy
Other causes of weakness and paralysis
Acute intermittent porphyria (ascending weakness)
Upper motor neuron:
CVA
Hemorrhagic stroke
Multiple sclerosis
Amyotrophic Lateral Sclerosis (ALS) (UMN & LMN)
Lower motor neuron:
Spinal and bulbar muscular atrophy (Kennedy's syndrome)
Spinal cord disease:
Infection (Epidural abscess)
Infarction/ischemia
Trauma (Spinal Cord Syndromes)
Inflammation (Transverse Myelitis)
Acute flaccid myelitis
Degenerative (Spinal muscular atrophy)
Tumor
Peripheral nerve disease:
Guillain-Barre syndrome
Toxins (Ciguatera)
Tick paralysis
Diabetic peripheral neuropathy
NMJ disease:
Myasthenia gravis crisis
Botulism
Organophosphate toxicity
Lambert-Eaton myasthenic syndrome
Muscle disease:
Rhabdomyolysis
Dermatomyositis<unk> 
Alcoholic myopathy
CVA
Hemorrhagic stroke
Multiple sclerosis
Amyotrophic Lateral Sclerosis (ALS) (UMN & LMN)
Spinal and bulbar muscular atrophy (Kennedy's syndrome)
Infection (Epidural abscess)
Infarction/ischemia
Trauma (Spinal Cord Syndromes)
Inflammation (Transverse Myelitis)
Acute flaccid myelitis
Degenerative (Spinal muscular atrophy)
Tumor
Acute flaccid myelitis
Guillain-Barre syndrome
Toxins (Ciguatera)
Tick paralysis
Diabetic peripheral neuropathy
Myasthenia gravis crisis
Botulism
Organophosphate toxicity
Lambert-Eaton myasthenic syndrome
Rhabdomyolysis
Dermatomyositis<unk> 
Alcoholic myopathy
Can't miss diagnoses:
ACS
Arrhythmia/Syncope
Severe infection/Sepsis
Hypoglycemia
Periodic paralysis (electrolyte disturbance, K, Mg, Ca)
Hypokalemic periodic paralysis
Thyrotoxic periodic paralysis
Respiratory failure
Emergent Diagnoses:
Symptomatic Anemia
Severe dehydration
Hypothyroidism
Polypharmacy
Malignancy
Other causes of weakness and paralysis
Acute intermittent porphyria (ascending weakness)
ACS
Arrhythmia/Syncope
Severe infection/Sepsis
Hypoglycemia
Periodic paralysis (electrolyte disturbance, K, Mg, Ca)
Hypokalemic periodic paralysis
Thyrotoxic periodic paralysis
Respiratory failure
Hypokalemic periodic paralysis
Thyrotoxic periodic paralysis
Symptomatic Anemia
Severe dehydration
Hypothyroidism
Polypharmacy
Malignancy
Acute intermittent porphyria (ascending weakness)
Polymyositis
Infection:
Dermatomyositis
Viral infection 
Lambert-Eaton myasthenic syndrome
Bacterial infection
Amyotrophic lateral sclerosis
Spirochete infection 