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Am Fam Physician. 2000;62(5):958-960

The article “Identification and Evaluation of Mental Retardation” (February 15, page 1059) contained an error in Table 2; the correct term for the fourth entry in the diagnosis column should be velocardiofacial syndrome rather than DiGeorge syndrome. The corrected table is reprinted on the following pages.

DiagnosisIncidenceEtiology, including inheritanceClinical manifestations and early recognitionAssociated conditionsDiagnostic evaluation*PrognosisSpecial considerations
Down syndrome1 in 600 to 800 birthsResults from extra copy of chromosome 21, usually a sporadic event; 2% of cases may be inherited from a balanced translocation carrier parentHypotonia; flat facial profile; upslanting palpebral fissures; small ears; in-curving fifth fingers; single transverse palmar creasesSlow growth; congenital heart defect; thyroid dysfunction; developmental delay, especially speechChromosome analysis in all patients; chromosome analysis of parents if translocation is found; pediatric cardiology evaluation with echocardiogram by 6 weeks of ageCognitive limitations, with most in mild to moderate MR range; decreased life expectancy can be associated with congenital heart defect, especially if not recognized in early infancyExcept in cases where parent has a translocation, risk for recurrence is 1%
Fetal alcohol syndrome0.05 to 3 in 1,000 children diagnosed annually in United StatesAlcohol consumption by mother during pregnancyDiagnosis can be made at birth, based on history, baby's facial features (medial epicanthal folds, wide nasal bridge, small upturned nose, long philtrum, narrow or wide upper lip), low birth measurementsMay include retardation, behavior problems, ADHD, seizures, autismGood history and physical examination imperative; history of maternal drinking, pre- and postnatal growth retardation, dysmorphic facial features, CNS involvement; no laboratory tests availableVaries; growth may improve during adolescence and facial features may soften, but behaviors may cause serious problemsMany of these children are adopted; FAS and fetal alcohol effects (usually developmental and behavioral problems) are totally preventable
Fragile X syndrome1 in 2,000 to 3,000 male live births; females may also be affectedAbnormality in FMR-1 gene located on X chromosome; inherited in X-linked manner so males are more severely affectedMacrocephaly; large ears; enlarged testicles after puberty; hyperextensible fingersAutism/autistic- like behaviors; developmental delay, especially speech; clumsiness; mitral valve prolapseDNA testing for fragile X mutation (chromosome testing for fragile X misses up to 7% of cases); mothers of affected boys are obligate carriers of the geneNormal life expectancy; mild to profound MRFemales usually less severely affected than males; up to 50% of females with mutation have MR or educational difficulties; risk for recurrence is 50%
Velocardio- facial syndrome1 in 700 live birthsDeletion of chromosome 22; usually de novo but may be inherited in an autosomal dominant mannerCleft palate; congenital heart defect; speech delay; elongated face with almond- shaped eyes; wide nose with hypoplastic alae nasi; small ears; slender, hyperextensible fingersLearning disabilities ± mild MR; psychiatric disorder in 10%High-resolution chromosome analysis with chromosome painting (FISH) to detect chromosome 22 deletion; parents should also be testedNormal life expectancy unless severe heart defect (e.g., truncus arteriosus, interrupted aortic arch) is presentRisk for recurrence as high as 50%, depending on family history
Unknown cause of MR30 to 50% of all cases of MRVariable; diagnosis may evolve over time, so repeated evaluations may be helpfulNonspecific cluster of minor malformations; delayed milestones, especially language developmentBehavioral phenotype may also aid diagnosis as course evolvesCytogenetic studies; brain imaging; metabolic studiesWill vary considerably based on etiology (if it can be established) and/or severityDiagnostic techniques that may aid in diagnosis are constantly being refined

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