Sandbox Myopathy

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

Flow chart

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

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
Medications
Corticosteroids	Variable	Proximal		-	+	-	-	-	+	-	-	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	Normal	Normal	Normal
Statins	60+	Proximal		-	+	-	-	-	-	-	-/+(rhabdomyolysis)	N/A	Positive medication history	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	nonspecific and are normal in many patients	Normal or ↑↑	Normal	Normal
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 usually are spared Overweight Straie Moon face HTN Hyperpigmentation	+ ACTH Stimulation test 24-hour urine cortisol Low dose dexamethasonesuppression 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' Swelling on neck examination	Decreased TSH	↑↑	Non specific	Myotonic
Hypothyroidism	>55	Proximal		-	+	+	-	-	+	+	+ Rhabdomyolysis	Signs of hypothyroidism	H/o weight gain	Myoedema  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	Elevation of the erythrocyte sedimentation rate Leukocytosis	Normal	Necrosis Edema	Normal
Inflammatory / Rheumatologic
Dermatomyositis	40s-50s Can affect childreen	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		↑↑	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 depressive disorder	Tenderness in the soft tissue anatomical location	Normal	Normal	Normal	Normal
Polymyalgia Rheumatica	50s	Diffuse		+	+	-	-	-	-	+	-	Weight loss	History of joints stiffness which is worse in the morning	Restricted shoulder motion	↑ CRP ↑ ESR	Normal	Normal	Normal
Genetic
Becker muscular dystrophy	<13yrs	Proximal		-	-	+	+	-	+	-	-	Milder form of Duchenne	Growth delay Age of onset of symptoms is much delayed than duchenne	+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	+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	↑↑	-	Myopathic
Myotonic dystrophy	<18 years	Proximal Distal		-	-	+	+	-	-	+	-	Myotonia Cataracts Diabetes mellitus Frontal balding Cardiac arrhythmias Cholecystitis Pregnancy Eyelid ptosis	+Family history	Muscles often contract and are unable to relax	Mutations in the DMPK gene	-	-	Myopathic
Infectious
Lyme disease	Variable	Proximal		+	+	-	+/-	+	-	-	-	Erythema Migrans Flu-like symptoms Lyme arthritis Neurological manifestations	+ Tick bite Hiking/Tip	Target-like lesions HSM	Clinical diagnosis +Serology	-	-	-
Influenza	Variable	Negative		+	+	-	+	-	-	-	+	Fever Malaise Rhinorrhea Muscle pain worse with movement	Cold weather H/o Ill contacts	Muscle weakness, tenderness, and swelling.	↑↑ Liver enzymes +PCR	↑↑	-	-
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 +Serology	-	-	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	-	-	-
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	-	-	-
Neurologic
ALS	>35	Proximal 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
Neuro-muscular
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
Hereditary
Glycogen storage disease	Variable	Proximal		-	-	-	-	-	+	-	-	AR Faituge Hypoglycemia	Exercise intolerance	Hypotonia Hepatomegaly	Lactic acidosis Elevated liver enzymes Ketosis	↑↑	Normal	Normal