Diagnosis of Fragile-X Syndrome
Diagnostic Test list for Fragile-X Syndrome:
The list of medical tests
mentioned in various sources as
used in the diagnosis of Fragile-X Syndrome
includes:
Fragile-X Syndrome Diagnosis: Book Excerpts
Diagnostic Tests for Fragile-X Syndrome: Online Medical Books
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MENTAL RETARDATION:
Ask the Following Questions:
(Algorithmic Diagnosis of Symptoms and Signs)
- Is there decreased hair and skin pigment? These findings would suggest phenylketonuria.
- Are there abnormal secondary sex characteristics? These findings would suggest Klinefelter's syndrome, Turner's syndrome, and Laurence-Moon-Bardet-Biedl syndrome.
- Are there abnormalities of the skull present? Findings of deformities or enlargement of the skull should suggest rickets, microcephaly, hypertelorism, oxycephaly, and hydrocephalus, among other things.
- Is there hepatosplenomegaly? The findings of hepatosplenomegaly suggest galactosemia, Hurler's disease, and Gaucher's disease, among other diagnostic possibilities.
- Are there skin changes? Sturge-Weber syndrome, tuberous sclerosis, neurofibromatosis, and cretinism may present with skin changes. Kernicterus is associated with jaundice.
- Are there other neurologic signs? Tay-Sachs disease, congenital syphilis, Arnold-Chiari malformation, and cerebral diplegia are just a few of the causes of mental retardation that may present with other neurologic signs.
DIAGNOSTIC WORKUP
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.
» READ BOOK EXCERPT ONLINE »
Source: Algorithmic Diagnosis of Symptoms and Signs, 2003
Fragile X syndrome:
Diagnosis
(Professional Guide to Diseases (Eighth Edition))
Confirming diagnosis
Diagnosis of fragile X syndrome requires identification of clinical symptoms and a positive genetic test. DNA analysis of blood or buccal samples is used to detect the size of the CGG repeat and the methylation status of FMR1.
A specific genetic test (polymerase chain reaction) can also be performed to diagnose this disease. This test looks for an expanded mutation (called a triplet repeat) in the FRAXA gene.
Before identification of the FMR1 mutation, a special cytogenetic (chromosome) blood test was used to microscopically detect the fragile site on the long arm of the affected X chromosome. It's now common knowledge that a full FMR1 mutation doesn't always result in a cytogenetically detectable fragile site. Therefore, chromosome analysis alone can provide false-negative results. Chromosome analysis still has utility together with FMR1 mutation analysis when performing a genetic evaluation on a male with mental retardation of unknown etiology.
In addition to diagnosing fragile X syndrome, genetic testing can determine whether the mother of a diagnosed individual is a carrier of the FMR1 premutation or has a full mutation. This information can be used for preconceptional genetic counseling by a trained professional and prenatal testing if the woman so chooses. FMR1 mutation analysis can also be subsequently performed on at-risk family members. It should be noted, however, that communication of genetic test results to at-risk family members constitutes a breech of patient confidentiality and privacy unless prior written permission to communicate results has been obtained from the previously tested patients.
» READ BOOK EXCERPT ONLINE »
Source: Professional Guide to Diseases (Eighth Edition), 2005
Mental retardation:
Diagnosis
(Professional Guide to Diseases (Eighth Edition))
CONFIRMING DIAGNOSIS A score of less than 70 on a standardized IQ test confirms the diagnosis of mental retardation.
The IQ test primarily predicts school performance and must be supplemented by other diagnostic evaluations.
For example, the Adaptive Behavior Scale deals with behaviors important to activities of daily living. This test evaluates self-help skills (toileting and eating), physical and social development, language, socialization, and time and number concepts. It also examines inappropriate behaviors, such as violent or destructive acts, withdrawal, and self-abusive or sexually aberrant behavior.
Age-appropriate adaptive behaviors are assessed by using developmental screening tests such as the Denver Developmental Screening test. These tests compare the subject’s functional level with the normal level for the same chronologic age. The greater the discrepancy between chronologic and developmental age, the more severe the retardation. In most European and North American cultures, the Vineland Social Maturity Scale, a tool used to determine social competence, is recommended for use when appropriate.
In children, the functional level is based on sensorimotor skills, self-help skills, and socialization. In adolescents and adults, it’s based on academic skills, reasoning and judgment skills, and social skills.
» READ BOOK EXCERPT ONLINE »
Source: Professional Guide to Diseases (Eighth Edition), 2005
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