Diagnostic Tests for Prader-Willi syndrome
Prader-Willi syndrome Tests: Book Excerpts
Prader-Willi syndrome Diagnosis: Book Excerpts
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Diagnostic Tests for Prader-Willi syndrome: Online Medical Books
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MENTAL RETARDATION:
DIAGNOSTIC WORKUP
(Algorithmic Diagnosis of Symptoms and Signs)
Routine laboratory tests include a CBC, sedimentation rate, chemistry panel, serum galactose level, VDRL test, thyroid profile, and urine screen for carbohydrates, amino acids, and organic acids. Chromosomal analysis may detect Klinefelter's syndrome, Turner's syndrome, mongolism, and other disorders. If there are deformities of the skull present, a skull x-ray should be done.
An EEG, CT scan of the brain, and psychometric testing will often need to be done, but a referral to a neurologist should be made before ordering these expensive tests.
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Source: Algorithmic Diagnosis of Symptoms and Signs, 2003
OBESITY, PATHOLOGIC:
DIAGNOSTIC WORKUP
(Algorithmic Diagnosis of Symptoms and Signs)
Routine laboratory tests include a CBC, urinalysis, chemistry panel, 2-hr postprandial blood sugar, and thyroid profile. If an insulinoma is strongly suspected, a 24- to 36-hr fast, a 5-hr glucose tolerance test, and tolbutamide tolerance test may be done. If Cushing's syndrome is suspected, a serum cortisol and cortisol suppression test should be done. Pelvic ultrasound will help diagnose polycystic ovaries. Chromosomal analysis will help diagnose Klinefelter's syndrome. Perhaps a psychiatrist should be consulted.
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Source: Algorithmic Diagnosis of Symptoms and Signs, 2003
CRAMPS, MUSCULAR:
DIAGNOSTIC WORKUP
(Algorithmic Diagnosis of Symptoms and Signs)
All patients should have a CBC, sedimentation rate, chemistry panel, electrolytes, and urinalysis. If there is associated diminished or absent peripheral pulses, then Doppler studies and arteriography should be done. If the cramps are acute in onset, time should not be wasted in performing these studies. Magnetic resonance angiography is an excellent alternative to invasive angiography, but it is expensive. If there is associated hypertension, then 24-hr urine aldosterone and plasma renin studies should be done. If there are positive Trousseau's and/or Chvostek's signs, a thorough investigation for hypoparathyroidism should be done. A single serum calcium and phosphorus and alkaline phosphatase is not enough, but repeated studies should be done. In addition, 24-hr urine collection for calcium and serum parathyroid hormones should be done. An endocrinologist should probably be consulted if there is any doubt about the existence of hypoparathyroidism or any of the other causes of hypocalcemia.
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Source: Algorithmic Diagnosis of Symptoms and Signs, 2003
Shortness of Breath:
Physical examination
(The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter)
In the physical examination, focus on signs of respiratory or cardiac disease. For the respiratory system, this means a careful examination starting at the nose. Specifically, on head, eyes, ear, nose, and throat examination look for evidence of obstruction, infection, or postnasal drip. Exclude obstruction, subcutaneous emphysema, or tracheal deviation. On cardiac examination, look for evidence of cardiomegaly, S3 gallop, or hepatojugular reflux (HJR). In this setting, HJR is very specific for CHF (1). Assess the lungs for abnormal breath sound intensity, rales, wheezing, rhonchi, or tachypnea. Examine the chest for abnormal movements or deformities. Exclude abdominal masses, ascites, pregnancy, or abdominal distention. Evaluate the extremities for edema, tenderness, or asymmetry. Do a complete neurologic examination, and screen for weakness atrophy, sensory loss, and fasciculations.
Testing
Most patients require a CXR study and pulse oximetry to screen for cardiac and pulmonary diseases. Use an arterial blood gas (ABG) analysis to confirm hypoxia, hypercapnia, hypocapnia, and acidosis. Complete blood count (CBC), electrolytes, thyroid-stimulating hormone (TSH), and drug screens are useful for suspected cases of anemia, acidosis, hyperthyroidism, hypothyroidism, or drug ingestions.
Pulmonary function studies (PFTs) are important to document the presence of obstructive or restrictive lung diseases. A methacholine challenge test is used if the symptoms are intermittent, the patient is aged less than 40 years, or if lung disease is suspected and the PFTs are normal. In this setting, the results will confirm or exclude asthma (3). In dyspneic patients, a lung diffusion capacity (DLCO) has a high positive predictive value and a high negative predictive value for interstitial lung disease (3). Low maximal inspiratory and expiratory pressures suggest neuromuscular disease.
The cardiac causes of dyspnea are CHF, intracardiac shunts, valvular heart disease, pulmonary hypertension, and pericardial disease. They have abnormal or characteristic findings on echocardiography and Doppler echocardiography. An electrocardiogram (ECG) or exercise stress test (EST) screens for arrhythmias and ischemic heart disease. Warning: A negative EST does not exclude ischemia in dyspneic patients (3) (Chapter 7.1).
Other tests are used in selected patients. High resolution computerized tomography (CT) of the chest detects early interstitial lung disease in patients with normal CXR films. Electromyogram (EMG) and nerve conduction studies are useful for confirming and differentiating the most common neuromuscular problems: myasthenia gravis and Guillain-Barré syndrome. A therapeutic response to H2 blockers confirms gastroesophageal reflux disease (GERD) in most dyspneic patients (2). Screen for acute or chronic pulmonary embolism with a nuclear medicine ventilation and perfusion (·V/Q·) scan.
Diagnostic assessment
The initial assessment usually requires a clinical evaluation, CXR study, and pulse oximetry. This identifies about 70% of the underlying diseases (1). For the remainder, a systematic evaluation for the most common diseases will correctly identify the cause. If appropriate, consider obtaining an ECG, CBC, TSH, and electrolytes. If theses are nondiagnostic, then further testing is indicated.
Exclude pulmonary diseases if the initial evaluation is nondiagnostic, or if pulmonary diseases are suspected, which account for 75% of the cases (3). Start with PFTs and an ABG. If the PFTs are normal, then order a methacholine challenge test to rule out asthma. If interstitial lung disease is suspected or if the PFTs show a restrictive pattern, then order a DLCO. Abnormally low maximal inspiratory and expiratory pressures suggest neuromuscular disease. Confirm the diagnosis with an EMG.
When pulmonary disease has been excluded, or if cardiac disease is suspected, the next step should be a cardiac evaluation. An echocardiogram will suggest or identify most of the cardiac causes. If the echocardiogram is normal, consider exercise stress testing or a Holter monitor. If these are normal, then most patients will have either GERD, deconditioning, or psychogenic disorders. Other low frequency causes of shortness of breath that need further evaluation include neuromuscular diseases, pulmonary emboli, postnasal drip, and sleep apnea. With a clinical suspicion of these disorders, obtain an EMG, ·V/Q· scan, or polysomnogram. Otherwise, they are not indicated.
References
1. Mulrow CD, Lucey CR, Farnett LE. Discriminating causes of dyspnea through clinical examination. J Gen Intern Med 1993;8:383–392.
2. DePaso WJ, Winterbauer RH, Lusk JA, Dreis DF, Springmeyer SC. Chronic dyspnea unexplained by history, physical examination, chest roentgenogram, and spirometry. Chest 1991;100:1293–1299.
3. Pratter MR, Curley FJ, Dubois J, Irwin RS. Cause and evaluation of chronic dyspnea in a pulmonary disease clinic. Arch Intern Med 1989;149:2277–2282.
4. Schmitt BP, Kushner MS, Wiener SL. The diagnostic usefulness of the history of the patient with dyspnea. J Gen Intern Med 1986;1:386–393.
5. Mahler DA, Harver A, Lentine T, Scott JA, Beck K, Schwartzstein M. Descriptors of breathlessness in cardiorespiratory diseases. Am J Respir Crit Care Med 1996;154:1357–1363.
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Source: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, 2000
Obesity:
Diagnostic Approach
(Field Guide to Bedside Diagnosis)
Body mass index (BMI) 5 mass (kilograms)/height (meters)2. Overweight is
a BMI 25 to 30 kg/m2 and obesity is a BMI .30 kg/m2. A body mass index .30 correlates with increased risk of type 2 diabetes, sleep apnea syndrome, fatty liver, gallstones, gout, degenerative joint disease, and accelerated atherogenesis. Abdominal obesity (waist–hip ratio .0.95 in men and .0.85 in women) with excess visceral (intra-abdominal) fat is associated with elevated trigylceride, insulin and glucose levels, and confers an especially increased incidence of adverse outcomes.
Less than 1% of patients with obesity have an endocrine or other secon-dary cause.
Rapid weight gain is usually due to fluid accumulation, seen with congestive heart failure, renal failure or chronic liver disease. Ascites with the latter can
produce a prominent abdomen, which can be mistaken for obesity by the patient.
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Source: Field Guide to Bedside Diagnosis, 2007
Hypotonia and Weakness:
Diagnostic Approach
(The Diagnostic Approach to Symptoms and Signs in Pediatrics)
First stepis to determine whether disorder involves nervous system includingneuromuscular system. This can usually be accomplished by historyand physical exam.If disorder involves nervous system,next step is to define anatomic level of abnormality—brain,spinal cord, anterior horn cell, peripheral nerve, neuromuscularjunction, or muscle. This can usually be accomplished by consideringdistinguishing features (e.g., pattern of weakness, deep tendonreflexes, presence of sensory loss or fasciculations, serum muscleenzyme levels, CSF findings, electromyographic pattern, nerve conductionvelocities, and muscle biopsy).Final step is to make specific diagnosis,which usually can be done by analysis of the above findings, otherclinical findings, and other investigations. Brain
Characteristicfindings with brain disorders include weakness of extremities (proximalas much as or more than distal), normal or increased deep tendonreflexes, seizures, developmental delay, and cognitive change.Degree of weakness is usually lessstriking than degree of hypotonia. Cranial nerve nuclei also maybe involved.Serum muscle enzymes, electromyography,and muscle biopsy are normal, except for particular disorders (e.g.,congenital muscle dystrophies) in which muscle and brain may beabnormal.Neuroimaging is useful in diagnosisof many of these disorders. Spinal Cord
Disordersaffecting spinal cord may produce flaccid weakness of all extremitiesif injury involves cervical region; usually normal or hypoactivedeep tendon reflexes, which can become hyperactive in next few weeksor months; sphincter abnormalities; and sensory level on trunk.Cranial nerve function is normal.MRI is useful in defining locationand extent of spinal cord lesion. Anterior Horn Cell
Characteristicfindings of spinal muscular atrophies include severe hypotonia and weakness(proximal as much as or more than distal), muscle fasciculations,and absence of deep tendon reflexes. Facial weakness also may occur.Sensory function, spinal fluid analysis, and serum muscle enzymelevels are normal.Fibrillations can be demonstrated byelectromyography.Muscle biopsy shows denervation patternin which hallmark is atrophy of group of muscle fibers. Enteroviralinfection affecting anterior horn cells commonly produces asymmetricweakness and abnormal spinal fluid. Peripheral Nerve
Characterizedby marked weakness (usually distal more than proximal), decreasedor absent deep tendon reflexes, abnormal sensory examination, increasedcerebrospinal fluid protein concentration, and decreased nerve conductionvelocities.Muscle biopsy shows denervation pattern,and nerve biopsy is usually abnormal. Neuromuscular Junction
Disordersof neuromuscular junction produce generalized weakness (proximalas much as distal). Facial weakness is usual finding, and extraocularmuscles may be involved. Deep tendon reflexes are usually normal.Sensory function, spinal fluid analysis, serum muscle enzyme levels,and muscle biopsy are normal.Electromyography shows characteristicdecremental response to repetitive stimulation with myasthenia gravis.There is usually positive response to neostigmine or edrophonium.Typical electromyographic findingsin botulism are incremental response with repetitive stimulationand frequent, brief duration, small amplitude motor unit potentials.Pupillary responses to light are impaired or absent with botulism. Muscle
Muscle disordersproduce weakness, with proximal weakness often more pronounced thandistal weakness. Facial weakness is variable but may occur withseveral muscle disorders. These include central core disease, myotubularmyopathy, nemaline myopathy, congenital fiber disproportion, congenitalmuscular dystrophy, facioscapulohumeral dystrophy, and myotonicdystrophy. Deep tendon reflexes are usually decreased in proportionto weakness.Sensory function and spinal fluid analysisare normal. Increased serum concentration of muscle enzymes is variable.Electromyography shows small-amplitude,short-duration motor unit potentials and myopathic polyphasic potentials.Muscle biopsy shows myopathic pattern,and nongrouped atrophy is essential feature.Various studies of muscle (histologic,histochemical, biochemical, immunocytochemical, electron microscopic)are often needed for diagnosis.Molecular genetic analysis can nowbe performed for definitive diagnosis of many muscle disorders.
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Source: The Diagnostic Approach to Symptoms and Signs in Pediatrics, 2006
Obesity:
Diagnostic Approach
(The Diagnostic Approach to Symptoms and Signs in Pediatrics)
If physicalexam and linear growth are normal, combination of genetic influencesand environmental factors is almost always the cause of obesity.If decreased linear growth occurs,glucocorticoid excess, hypothyroidism, and growth hormone deficiencyshould be considered.Many unusual syndromes associated withobesity may be distinguished by their clinical findings and moleculargenetic analysis.
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Source: The Diagnostic Approach to Symptoms and Signs in Pediatrics, 2006
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