Sandbox Myopathy

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

Differentiating Various Muscle Weakness

Disease	Symptoms									History	Physical Examination	Diagnosis
	Age of onset	Muscle weakness		Fever	Muscle pain	Gait abnormality	Neuropathy	Myoglobinuria	Other features			Laboratory Findings		Creatine Kinase	Muscle Biopsy	Electromyogram
		Proximal	DIstal
Medications
Corticosteroids	Variable	+	-	-	+	-	-	-	Central obesity Excessive sweating Insomnia Reduced libido  Amenorrhea Infertility  Psychological disturbances	+ History of medications	Facial and sphincter muscles usually are spared	+ ACTH Stimulation test 24-hour urine cortisol Low dose dexamethasone suppression test		-	-	-
Statins	60+	+	-	-	+	-	-	-/+(rhabdomyolysis)	N/A	Positive medication history	Tenderness Muscle aches	↑↑ liver enzymes		↑↑	Necrosis Degeneration, and regeneration of fibers Phagocytic infiltration	-
Chemotherapeutic						-
Organophosphate intoxication						-
Alcohol	Variable	+				+					Change in mental status Telangiectasia Peripheral neuropathy
Endocrine
Cushing's disease
Adrenal insufficiency
Secondary hyperparathyroidism
Hyperthyroidism
Hypothyroidism
Inflammatory / Rheumatologic
Dermatomyositis	40s-50s Can affect childreen	+	-	+	+	-	-	-	Rash Dyspnea Weight loss Cough		Heliotrope rash on face and hands Telangectasia Erythema Mechanic's hands Gottron's sign ( violaceous scaly eruption )			↑↑	Perimysial mononuclear infiltrate	Muscle inflammation and damage
Polymyositis	> 18 years	+	-	+	+	-	-	-	-		-			↑↑	Endomysial mononuclear infiltrate Patchy necrosis
Inclusion body myositis	50s	+	+											↑↑
Fibomyalgia	40-50s	+	-	-	-	-	++	-	Anxiety or depression features Fatigue Sleep disturbance Numbness Muscle spasms	History of depressive disorder	Tenderness in the soft tissue anatomical location	Normal		Normal	Normal	Normal
Polymyalgia Rheumatica	50s	+	-	+	+	-	-	-	Weight loss	History of joints stiffness which is worse in the morning	Restricted shoulder motion	↑ CRP ↑ ESR		Normal	Normal	Normal
Chronic Pain Syndrome
Genetic
Becker muscular dystrophy	<13yrs	+	-	-	-	+	-	-	Milder form of Duchenne			Decreased amount of dystrophin.		↑↑	Muscle fibril degeneration, regeneration Isolated fiber hypertrophy Muscle replacement with fat and connective tissue	Weakness is caused by destruction of muscle.
Duchenne muscular dystrophy	<13 yrs	+	-	-	-	+	-	-	Calf psedohypertrophy Cardiomyopathy Kyphoscoliosis Cognitive impairment		+Grower sign	Errors in the Xp21 gene. Absence of dystrophin.		↑↑
Limb-girdle muscular dystrophies	<15 yrs	+	-	-	+	+	-	-	Calf hypertrophy Scapular winging Cardiomyopathy Cardiac arrhythmias Respiratory muscle weakness	Autosomal dominant		LMNA gene CAV3 gene		↑↑	-
Myotonic dystrophy type 1		+	+	-	-	+	-	-	Myotonia Cataracts Diabetes mellitus Frontal balding Cardiac arrhythmias Cholecystitis Pregnancy Eyelid ptosis
Infectious
Lyme disease	Variable	+	-	+	+	+/-	+	-	Erythema Migrans Flu-like symptoms Lyme arthritis Neurological manifestations	+ Tick bite Hiking/Tip	Target-like lesions HSM	Clinical diagnosis +Serology		-	-	-
Infulenza	Variable	-	-	+	+	+	-	+	Fever Malaise Rhinorrhea Muscle pain worse with movement		Muscle weakness, tenderness, and swelling.	↑↑ Liver enzymes +PCR		↑↑	-	-
Polio	<5 yrs	+	-	-	-	+	+	-	Asymmetrical paralysis Muscle atrophy Tremors Skeletal deformities		Normal Meningeal signs Asymmetrical flaccid paralysis Pharyngeal paralysis	Isolation from pharyngealsecretions, CSF +Serology		-	-	Neurological pattern
Syphilis	Variable	-	-	-	-	+	+	-	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		-	-	-
Pyomyositis	Variable	+/-	+/-	+	+	-	-	-	Fever Malaise Psoas abscess	Immunocopmprimised	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		-	-	-
Neurologic
ALS
Stroke
GBS
Multiple Sclerosis
Neuro-muscular
Botulisim
Lambert-Eaton myaes
Myasthenia gravis
Paraneoplastic
Metabolic
Glycogen storage disease
Lipid storage disease
Mitochondrial