Duchenne muscular dystrophy

Duchenne muscular dystrophy is an inherited disorder that involves rapidly worsening muscle weakness.

Causes

Duchenne muscular dystrophy is a rapidly-worsening form of muscular dystrophy. Other muscular dystrophies (including Becker's muscular dystrophy) get worse much more slowly.

Duchenne muscular dystrophy is caused by a defective gene for dystrophin (a protein in the muscles). However, it often occurs in people without a known family history of the condition.

Because of the way the disease is inherited, males are more likely to develop symptoms than are women. The sons of females who are carriers of the disease (women with a defective gene but no symptoms themselves) each have a 50% chance of having the disease. The daughters each have a 50% chance of being carriers.

Duchenne muscular dystrophy occurs in approximately 1 out of every 3,600 male infants. Because this is an inherited disorder, risks include a family history of Duchenne muscular dystrophy.

Symptoms

Symptoms usually appear before age 6 and may appear as early as infancy. They may include:

• Fatigue
• Mental retardation (possible, but does not worsen over time)
• Muscle weakness
• Begins in the legs and pelvis, but also occurs less severely in the arms, neck, and other areas of the body
• Difficulty with motor skills (running, hopping, jumping)
• Frequent falls
• Rapidly worsening weakness
• Progressive difficulty walking
• Ability to walk may be lost by age 12

By age 10, the person may need braces for walking. By age 12, most patients are confined to a wheelchair.

Exams and Tests

A complete nervous system (neurological), heart, lung, and muscle exam may show:

• Abnormal heart muscle (cardiomyopathy)
• Congestive heart failure or irregular heart rhythm (arrhythmias) -- rare
• Deformities of the chest and back (scoliosis)
• Enlarged calf muscles, which are eventually replaced by fat and connective tissue (pseudohypertrophy)
• Loss of muscle mass (wasting)
• Muscle contractures in the heels, legs
• Muscle deformities
• Respiratory disorders, including pneumonia and aspiration of food or fluid into the lungs (in late stages of the disease)

Tests may include:

• Electromyography (EMG)
• Genetic tests
• Muscle biopsy
• Serum CPK

Treatment

There is no known cure for Duchenne muscular dystrophy. Treatment aims to control symptoms to maximize quality of life. Gene therapy may become available in the future.

Activity is encouraged. Inactivity (such as bedrest) can worsen the muscle disease. Physical therapy may be helpful to maintain muscle strength and function. Orthopedic appliances (such as braces and wheelchairs) may improve mobility and the ability to care for yourself.

Outlook (Prognosis)

Duchenne muscular dystrophy leads to quickly worsening disability. Death usually occurs by age 25, typically from lung disorders.

Possible Complications

• Cardiomyopathy
• Congestive heart failure (rare)
• Deformities
• Heart arrhythmias (rare)
• Mental impairment (varies, usually minimal)
• Permanent, progressive disability
• Decreased mobility
• Decreased ability to care for self
• Pneumonia or other respiratory infections
• Respiratory failure

Alternative Names

Pseudohypertrophic muscular dystrophy; Muscular dystrophy - Duchenne type

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Becker muscular dystrophy

Becker muscular dystrophy is an inherited disorder that involves slowly worsening muscle weakness muscle weakness of the legs and pelvis.

Causes

Becker muscular dystrophy is very similar to Duchenne muscular dystrophy, except that it gets worse at a much slower rate.

The disorder is passed down through families (inherited). Having a family history of the condition raises your risk.

Becker muscular dystrophy occurs in approximately 3 - 6 out of every 100,000 males. It is less common than Duchenne muscular dystrophy.

Symptoms

Females rarely develop symptoms. Males will develop symptoms if they inherit the defective gene. Symptoms usually appear in boys at about age 12, but may begin later.

Muscle weakness of the lower body, including the legs and pelvis area, slowly gets worse, causing:

• Difficulty walking that gets worse over time; by age 25-30 the person is usually unable to walk
• Frequent falls
• Difficulty with running, hopping, and jumping
• Loss of muscle mass

Muscle weakness in the arms, neck, and other areas is not as severe as in the lower body.

Other symptoms may include:

• Breathing problems
• Cognitive problems (these do not get worse over time)
• Fatigue
• Loss of balance and coordination

Exams and Tests

The health care provider will do a nervous system (neurological) and muscle examination. A careful medical history is also important, because the pattern of symptom development resembles that of Duchenne's muscular dystrophy. However, Becker muscular dystrophy gets worse much more slowly.

An exam may find:

• Abnormally developed bones, leading to deformities of the chest and back (scoliosis)
• Abnormality of heart muscle function (cardiomyopathy)
• Congestive heart failure or irregular heartbeat (arrhythmias) - rare
• Muscle deformities, including:
• Contractures of heels and legs
• Abnormal fat and connective tissue in calf muscles
• Muscle loss that begins in the legs and pelvis, then moves on to the muscles of the shoulders, neck, arms, and respiratory system

Tests that may be done include:

• CPK blood test
• Electromyography (EMG) nerve testing
• Muscle biopsy or genetic blood test

Treatment

There is no known cure for Becker muscular dystrophy. The goal of treatment is to control symptoms to maximize the person's quality of life. Some doctors prescribe steroids to help keep a patient walking for as long as possible.

Activity is encouraged. Inactivity (such as bed rest) can make the muscle disease worse. Physical therapy may be helpful to maintain muscle strength. Orthopedic appliances such as braces and wheelchairs may improve mobility and self-care.

Genetic counseling may be recommended. Daughters of a man with Becker muscular dystrophy may carry the defective gene and could pass it onto their sons.

Outlook (Prognosis)

Becker muscular dystrophy leads to slowly worsening disability, although the degree of disability varies. Some men may need a wheelchair, while others may only need to use walking aids such as canes or braces.

Possible Complications

• Heart-related complications such as cardiomyopathy
• Lung failure
• Pneumonia or other respiratory infections
• Increasing and permanent disability, that leads to:
• Decreased ability to care for self
• Decreased mobility

Alternative Names

Benign pseudohypertrophic muscular dystrophy; Becker's dystrophy

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NORMAL LABORATORY VALUES

NORMAL LABORATORY VALUES

Laboratory Test	Normal Range in US Units	Normal Range in SI Units	To Convert US to SI Units
ALT (Alanine aminotransferase)	W 7-30 units/liter M 10-55 units/liter	W 0.12-0.50 µkat/liter M 0.17-0.92 µkat/liter	x 0.01667
Albumin	3.1 - 4.3 g/dl	31 - 43 g/liter	x 10
Alkaline Phosphatase	W 30-100 units/liter M 45-115 units/liter	W 0.5-1.67 µkat/liter W 0.75-1.92 µkat/liter	x 0.01667
Amylase (serum)	53-123 units/liter	0.88-2.05 nkat/liter	x 0.01667
AST (Aspartate aminotransferase)	W 9-25 units/liter M 10-40 units/liter	W 0.15-0.42 µkat/liter M 0.17-0.67 µkat/liter	x 0.01667
Basophils	0-3% of lymphocytes	0.0-0.3 fraction of white blood cells	x 0.01
Bilirubin - Direct	0.0-0.4 mg/dl	0-7 µmol/liter	x 17.1
Bilirubin - Total	0.0-1.0 mg/dl	0-17 µmol/liter	x 17.1
Blood pressure	Normal: 120/70 to 120/80 millimeters of mercury (mmHg). The top number is systolic pressure, when the heart is pumping. Bottom number is diastolic pressure then the heart is at rest. Blood pressure can be too low (hypotension) or too high (hypertension).		No conversion
C peptide	0.5-2.0 ng/ml	0.17-0.66 nmol/liter	x 0.33
Calcium, serum	8.5 -10.5 mg/dl	2.1-2.6 mmol/liter	x 0.25
Calcium, urine	0-300 mg/24h	0.0-7.5 mmol/24h	x 0.025
Cholesterol, total Desirable Marginal High	239 mg/dL	6.18 mmol/liter	x 0.02586
Cholesterol, LDL Desirable Marginal High Very High	190 mg/dL	4.91 mmol/liter	x 0.02586
Cholesterol, HDL Desirable Moderate Low (heart risk)	>60 mg/dL 40-60 mg/dL	>1.55 mmol/liter 1.03-1.55 mmol/liter	x 0.02586
Cortisol: serum	0-25 µg/dl (depends on time of day)	0-690 nmol/liter	x 27.59
Cortisol: free (urine)	20-70 µg/dl	55-193 nmol/24h	x 2.759
Creatine kinase	W 40-150 units/liter M 60-400 units/liter	W 0.67-2.50 µkat/liter M 1.00-6.67 µkat/liter	x 0.01667
DHEA	W 130-980 ng/dl M 180-1250 ng/dl	W 4.5-34.0 nmol/liter M 6.24-43.3 nmol/liter	x 0.03467
DHEA Sulfate	W Pre-menopause: 12-535 µg/dl W Post-menopause: 30-260 µg/dl M 10-619 µg/dl	W Pre-menopause: 120-5350 µg/liter W Post-menopause: 300-2600 µg/liter M 100-6190 µg/liter	x 10
Eosinophils	0-8% of white blood cells	0.0-0.8 fraction of white blood cells	x 0.01
Erythrocyte sedimentation rate (Sed Rate)	W<=30 mm/h M<=20 mm/h	W<=30 mm/h M<=20 mm/h	No conversion
Folate	3.1-17.5 ng/ml	7.0-39.7 nmol/liter	x 2.266
Glucose, urine	<0.05>	<0.003>	x 0.05551
Glucose, plasma	70-110 mg/dl	3.9-6.1 mmol/liter	x 0.05551
GGT (Gamma glutamyl transferase)	W <=45U/L M <=65 U/L	W <=45U/L M <=65 U/L	No conversion
Hematocrit	W 36.0% - 46.0% of red blood cells M 37.0% - 49.0% of red blood cells	W 0.36-0.46 fraction of red blood cells M 0.37-0.49 fraction of red blood cells	x 0.01
Hemoglobin	W 12.0-16.0 g/dl M 13.0-18.0 g/dl	W 7.4-9.9 mmol/liter M 8.1-11.2 mmol/liter	x 0.6206
LDH (Lactate dehydrogenase) (total)	<=270 U/L	<=4.5 µkat/liter	x 0.016667
Lactic acid	0.5-2.2 mmol/liter	0.5-2.2 mmol/liter	No conversion
Leukocytes (WBC)	4.5-11.0x103/mm3	4.5-11.0x109/liter	No conversion
Lymphocytes	16%-46% of white blood cells	0.16-0.46 fraction of white blood cells	x 0.01
Mean corpuscular hemoglobin (MCH)	25.0-35.0 pg/cell	25.0-35.0 pg/cell	No conversion
Mean corpuscular hemoglobin concentration (MCHC)	31.0-37.0 g/dl	310-370 g/liter	x 10
MCV (Mean corpuscular volume)	W 78-102 µm3 M 78-100 µm3	W 78-102 fl M 78-100 fl	No conversion
Monocytes	4-11% of white blood cells	0.04-0.11 fraction of white blood cells	x 0.01
Neutrophils	45%-75% of white blood cells	0.45-0.75 fraction of white blood cells	x 0.01
Phosphorus	2.5 – 4.5 mg/dL	0.81-1.45 mmol/L	x 0.323
Platelets (Thrombocytes)	130 – 400 x 10 3µL	130 – 400 x 10 9L	No conversion
Potassium	3.4-5.0 mmol/liter	3.4-5.0 mmol/liter	No conversion
RBC (Red blood cell count)	W 3.9 – 5.2 x 106/µL3 M 4.4 – 5.8 x 10 6/µL3	W 3.9 – 5.2 x 1012/L M 4.4 – 5.8 x 10 12/L	No conversion
Sodium	135-145 mmol/liter	135-145 mmol/liter	No conversion
Testosterone, total (morning sample)	W 6-86 ng/dl M 270-1070 ng/dl	W 0.21-2.98 nmol/liter M 9.36-37.10 nmol/liter	x 0.03467
Testosterone, free Age 20-40 Age 41-60 Age 61-80	W 0.6-3.1, M 15.0-40.0 pg/ml W 0.4-2.5, M 13.0-35.0 pg/ml W 0.2-2.0, M 12.0-28.0 pg/ml	W 20.8-107.5, M 520-1387 pmol/liter W 13.9-86.7, M 451-1213 pmol/liter W 6.9-69.3, M 416-971 pmol/liter	x 34.67
Triglicerides (fasting) Normal Borderline High Very high	40-150 mg/dl 150-200 mg/dl 200-500 mg/dl >500 mg/dl	0.45-1.69 mmol/liter 1.69-2.26 mmol/liter 2.26-5.65 mmol/liter >5.65 mmol/liter	x 0.01129
Urea, plasma (BUN)	8-25 mg/dl	2.9-8.9 mmol/liter	x 0.357
Urinalysis - pH Specific gravity	5.0-9.0 1.001-1.035	5.0-9.0 1.001-1.035	No conversion
WBC (White blood cells, leukocytes)	4.5-11.0x10 3 /mm 3	4.5-11.0x10 9 liter	No conversion

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TERMINOLOGY:

UNITS:

gram : common measurement of weight. Used in this table: pg (picograms), g (grams), mg (milligrams), etc. per liter
katal (kat) : a unit of catalytic activity, used especially in the chemistry of enzymes. Used in this table: µkat (microkatals), nkat (nanokatals) per liter
micrometer (µm) : a unit of length. Mean Corpuscular Volume is expressed in cubic micrometers
mole : also “gram molecular weight,” a quantity based on the atomic weight of the substance. Many test results in the Système Internationale are expressed as the number of moles per liter. In US units, these measurements are usually in grams per liter. Used in this table: mmol (millimoles), µmol, (micromoles), nmol (nanomoles), pmol (picomoles) per liter

Some units of measurement include the following fractions and multipliers:
mega (M) : 10 ⁶ or x1,000,000
kilo (k) : 10 ³ or x1,000
deca or deka : 10 ¹ or x10
deci (d) : 10 ^-1 or ÷10
milli (m) : 10 ^-3 or ÷1,000
micro (µ) : 10 ^-6 or ÷1,000,000
nano (n) : 10 ^-9 or ÷1,000,000,000
pico (p) : 10 ^-12 or ÷1,000,000,000,000

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