Sandbox Myopathy

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Flow chart

Approach to muscle weakness

Objective Muscle weakness

Yes

No

Malignancy Arthralgia Anemia Firbomyalgia

Generalized

Localized

Myasthenia gravis Periodic paralysis

Asymmetric

Symmetric

Cerebrovascular accidents Demyleinating disorders Atrophy Mononeuropathy

Specific pattern

Specific pattern

Proximal

Hereditary neuropathy Muscular dystrophy

Myoapthy Duchenne muscular dystrophy

Motor neuron disease Peripheral neuropathy

Differentiating Various Muscle Weakness

Organ system	Disease	Symptoms												History	Physical Examination	Diagnosis
		Age of onset	Muscle weakness	Fever	Myalgia	Contractures	Gait abnormality	Neuropathy	Atrophy	Stiffness	Myoglobinuria	Other features	Laboratory Findings			Creatine Kinase	Muscle Biopsy	Electromyogram
Medication−induced	Corticosteroids	Variable	Proximal	−	+	−	−	−	+	−	−	Central obesity Excessive sweating Insomnia Reduced libido  Amenorrhea Infertility  Psychological disturbances	Positive h/o medications	Facial and sphincter muscles are usually spared	Positive ACTH stimulation test 24-hour urine cortisol Low dose dexamethasone suppression test	Normal	Normal	Normal
	Statins	60+	Proximal	−	+	−	−	−	−	−	−/+(Rhabdomyolysis)	N/A	Positive h/o medications H/o other medication use	Tenderness Muscle aches	↑↑ Liver enzymes	↑↑	Necrosis Degeneration, and regeneration of fibers Phagocytic infiltration	Normal
	Alcohol	Variable	Proximal	−	−	−	+	+/−	−	−	−	Swelling Tender Erythema and induration	Alcohol intoxication	Change in mental status Telangiectasia Peripheral neuropathy	Monspecific and are normal in many patients	Normal or ↑↑	Normal	Normal
Organ system	Disease	Age of onset	Muscle weakness	Fever	Myalgia	Contractures	Gait abnormality	Neuropathy	Atrophy	Stiffness	Myoglobinuria	Other features	History	Physical Examination	Laboratory Findings	Creatine Kinase	Muscle Biopsy	Electromyogram
Endocrine	Cushing's disease	25 −45	Proximal	−	−	−	−	−	+	−	−	Decreased libido Obesity/weight gain Plethora Round face Menstrual changes Hirsutism Hypertension Ecchymoses Lethargy Depression Dorsal fat pad Abnormal glucose tolerance	N/A	Facial and sphincter muscles are usually spared Overweight Straie Moon face HTN Hyperpigmentation	Positive ACTH stimulation test 24-hour urine cortisol Low dose dexamethasone suppression test	Normal	Atrophy of type 2 muscle fibers, especially type 2B	Normal
	Adrenal insufficiency	30−50 years	Proximal	−	+	−	−	−	−	+	−	Signs of glucocorticoid, mineralocorticoid, and, androgen deficiency	Signs of postural hypotension History of tuberculosis History of malignancy History of other autoimmune disease	Hypotension  Hyperpigmentation  Auricular−cartilage calcification  Vitiligo	Electrolyte abnormalities Hypoglycemia	Normal	Normal	Normal
	Hyperaldosteronism with myopathy	50	Proximal & distal	−	−	−	−	−	−	−	+ Rhabdomyolysis	Palpitations Hypertension	Episodes of increased heart beats	Hyperpigmentation	Hypokalemia	Normal	Normal	Normal
	Hyperthyroidism	40	Proximal	−	−	−	−	−	+	+	+	Signs of hyperthyroidism	H/o of weight loss	Sweating Tremor Neck swelling	Decreased TSH	↑↑	Non specific	Myotonic
	Hypothyroidism	55	Proximal	−	+	+	−	−	+	+	+ Rhabdomyolysis	Signs of hypothyroidism	H/o weight gain	Myxoedema  Muscle pseudohypertrophy	Increased TSH	↑↑	Nonspecific	Normal
	Diabetic infraction	45	Proximal	+	+	−	−	+	+	−	−	Cramps Sudden onset of pain Anterior thigh muscles are most commonly involved	H/O long standing diabetes	Swelling Tenderness	Elevated ESR Leukocytosis	Normal	Necrosis Edema	Normal
Organ system	Disease	Age of onset	Muscle weakness	Fever	Myalgia	Contractures	Gait abnormality	Neuropathy	Atrophy	Stiffness	Myoglobinuria	Other features	History	Physical Examination	Laboratory Findings	Creatine Kinase	Muscle Biopsy	Electromyogram
Inflammatory/ Rheumatologic	Dermatomyositis	40s−50s Can affect children	Proximal	+	+	−	−	−	−	+	−	Rash Dyspnea Weight loss Cough	Viral infections Cancer	Heliotrope rash on face and hands Telangiectasia Erythema Mechanic's hands Gottron's sign ( violaceous scaly eruption )	↑↑ ESR ↑↑ CRP	↑↑	Perimysial mononuclear infiltrate	Myopathic
	Polymyositis	> 18 years	Proximal	+	+	−	−	−	−	+	−	Similar to dermatomyositis without mucous and skin involvement	N/A	N/A	↑↑ ESR ↑↑ CRP	↑↑	Endomysial mononuclear infiltrate Patchy necrosis
	Inclusion body myositis	50s	Proximal & distal	−	−	−	−	−	−	−	−	Dysphagia Asymmetric weakness	Retrovirus (most common)	N/A	Antibodies to cytoplasmic 5'−nucleotidase	↑↑	Inflammatory cells Invading muscle cells Vacuolar degeneration Inclusions or plaques	Neurogenic
	Fibromyalgia	40−50s	Generalized	−	−	−	−	+	−	−	−	Anxiety or depression features Fatigue Sleep disturbance Numbness Muscle spasms	History of depression	Tenderness in the soft tissue anatomical location	Normal	Normal	Normal	Normal
	Polymyalgia Rheumatica	50s	Diffuse	+	+	−	−	−	−	+	−	Weight loss	History of joints stiffness, worse in the morning	Restricted shoulder motion	↑↑ ESR ↑↑ CRP	Normal	Normal	Normal
	Necrotizing autoimmune myopathy	30-70	Proximal & distal												Anti-SRP Anti-HMGCoAR autoantibodies	↑↑
Organ system	Disease	Age of onset	Muscle weakness	Fever	Myalgia	Contractures	Gait abnormality	Neuropathy	Atrophy	Stiffness	Myoglobinuria	Other features	History	Physical Examination	Laboratory Findings	Creatine Kinase	Muscle Biopsy	Electromyogram
Genetic	Becker muscular dystrophy	<13yrs	Proximal	−	−	+	+	−	+	−	−	Milder form of Duchenne	Growth delay Age of onset of symptoms is much delayed than duchenne	Positive Grower sign	Decreased amount of dystrophin.	↑↑	Muscle fibril degeneration, regeneration Isolated fiber hypertrophy Muscle replacement with fat and connective tissue	Myopathic
	Duchenne muscular dystrophy	<13 yrs	Proximal	−	−	+	+	−	+	−	−	Calf psedohypertrophy Cardiomyopathy Kyphoscoliosis Cognitive impairment	Early onset	Positive Grower sign	Errors in the Xp21 gene. Absence of dystrophin.	↑↑
	Limb−girdle muscular dystrophies	<15 yrs	Proximal	−	+	+	+	−	+	−	−	Calf hypertrophy Scapular winging Cardiomyopathy Cardiac arrhythmias Respiratory muscle weakness	Autosomal dominant Deterioration of ability to run/walk	Muscle weakness is generally symmetric	LMNA gene CAV3 gene	↑↑	N/A	Myopathic
	Myotonic dystrophy	<18 years	Proximal & distal	−	−	+	+	−	−	+	−	Myotonia Cataracts Diabetes mellitus Frontal balding Cardiac arrhythmias Cholecystitis Pregnancy Eyelid ptosis	Positive family history	Muscles often contract and are unable to relax	Mutations in the DMPK gene	N/A	N/A	Myopathic
	Glycogen storage disease	Variable	Proximal	−	−	−	−	−	+	−	−	AR Faituge Hypoglycemia	Exercise intolerance	Hypotonia Hepatomegaly	Lactic acidosis Elevated liver enzymes Ketosis	↑↑	Normal	Normal
Organ system	Disease	Age of onset	Muscle weakness	Fever	Myalgia	Contractures	Gait abnormality	Neuropathy	Atrophy	Stiffness	Myoglobinuria	Other features	History	Physical Examination	Laboratory Findings	Creatine Kinase	Muscle Biopsy	Electromyogram
Infectious	Lyme disease	Variable	Proximal	+	+	−	+/−	+	−	−	−	Erythema Migrans Flu−like symptoms Lyme arthritis Neurological manifestations	H/o tick bite Hiking trip	Target−like lesions HSM	Clinical diagnosis +Serology	N/A	N/A	N/A
	Influenza	Variable	style="background:#F5F5F5;" align="center" + |Negative	+	+	−	+	−	−	−	+	Fever Malaise Rhinorrhea Muscle pain worse with movement	Cold weather H/o Ill contacts	Muscle weakness, tenderness, and swelling.	↑↑ Liver enzymes Positive PCR	↑↑	N/A	N/A
	Polio	<5 yrs	Proximal	−	−	−	+	+	+	−	−	Asymmetrical paralysis Muscle atrophy Tremors Skeletal deformities	History of skipped immunization.	Normal Meningeal signs Asymmetrical flaccid paralysis Pharyngeal paralysis	Isolation from pharyngealsecretions, CSF Positive serology	N/A	N/A	Neurological pattern
	Syphilis	Variable	Negative	−	−	−	+	+	−	−	−	Chancre Lymphadenopathy Condylomata lata Neuro syphilis Cardiovascular syphilis	History of risk factors (MSM, unprotected sex, multiple sex partners)	Non−tender chancre in primary syphilis. Followed by rash Generalized lymphadenopathy in secondary syphilis	Darkfield examinations VDRL RPR FTA−ABS	N/A	N/A	N/A
	Pyomyositis	Variable	Proximal & Distal	+	+	−	−	−	−	+	−	Fever Malaise Psoas abscess	Immunocompromised	Muscles are painful, swollen, tender, and indurated. Depending on the site of involvement, it may mimic appendicitis (psoas muscle), septic arthritis of the hip (iliacus muscle), or epidural abscess (piriformis muscle).	Leukocytosis Elevated ESR	N/A	N/A	N/A
Organ system	Disease	Age of onset	Muscle weakness	Fever	Myalgia	Contractures	Gait abnormality	Neuropathy	Atrophy	Stiffness	Myoglobinuria	Other features	History	Physical Examination	Laboratory Findings	Creatine Kinase	Muscle Biopsy	Electromyogram
Neurologic	ALS	>35	Proximal & Distal Distal	−	−	−	−	+	+	+	−	Dysphagia Spasticity Hyperreflexia Babinski's +	N/A	Both upper and lower motor neuron signs	Clinical diagnosis	Normal	Nonspecific findings of chronic denervation with reinnervation	Neuropathic
	Stroke	>65	Proximal & distal	−	−	−	+	+	+	−	−	Dysphagia Unilateral/Bilateral weakness	H/o HTN, dyslipidaemia DM	Weakness of the involved arm	Head CT	Normal	Normal	Neuropathic
	GBS	18 −350	Proximal	−	−	−	+	−	−	+	−	Ascending paralysis	Precedes a gastrointestinal disease	Weakness of lower extremities followed by upper extremities	Cytologic albumin ratio	Normal	Normal	Neuropathic
	Multiple Sclerosis	30's	Proximal & distal	−	−	−	+	+	−	−	−	Ocular findings Urinary incontinence Problems with speech or swallowing	Attacks or exacerbation	Localized weakness Focal sensory disturbances Hyper reactive reflexes Increased tone or stiffness	Head CT ologo−clonal bands	Normal	N/A	Neuropathic
Organ system	Disease	Age of onset	Muscle weakness	Fever	Myalgia	Contractures	Gait abnormality	Neuropathy	Atrophy	Stiffness	Myoglobinuria	Other features	History	Physical Examination	Laboratory Findings	Creatine Kinase	Muscle Biopsy	Electromyogram
Neuromuscular	Botulinum	Variable	Distal	−	−	−	+	−	−	+	−	Double vision Blurred vision Drooping eyelids Slurred speech Difficulty swallowing	H/O food exposure	Hyporeflexia Decreased strength	+Toxin	Normal	N/A	Myopathic
	Lambert−Eaton syndrome	Variable	Distal	−	−	+	+	−	−	+	−	Weakness of the bulbar muscles Ocular Limb weakness	Weaknessa is often relieved temporarily after exertion or physical exercise.		Antibodies against voltage−gated calcium channels
	Myasthenia gravis	Variable	Proximal	−	−	+	+	−	−	+	−	Ocular Bulbar  Limb weakness Isolated neck, limbs and respiratory weakness	Weakness often worsens with activity		Antibodies that block or destroy nicotinic acetylcholine receptors