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
Polymyositis
Inclusion body myositis
Fibomyalgia
Polymyalgia Rheumatica
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	+/-	+/-	+	+	-
Neurologic
ALS
Stroke
GBS
Multiple Sclerosis
Neuro-muscular
Botulisim
Lambert-Eaton myaes
Myasthenia gravis
Paraneoplastic
Metabolic
Glycogen storage disease
Lipid storage disease
Mitochondrial