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A frequent multiple congenital anomaly/mental retardation syndrome of unknown etiology which affects 1/10,000 newborn infants. The most commonly occurring defects include growth deficiency, retarded psychomotor development, upper limb abnormalities, microbrachycephaly, and peculiar hair patterns giving the face its characteristic appearance, frequently associated with various neurological, behavioral, cardiovascular, gastrointestinal, dermatoglyphic abnormalities, and occasional Sandifer anomaly (abnormal body posturing, torticollis, and gastro-esophageal reflux with or without a hiatus hernia). The phenotype is variable and the affected infants may show different clusters of abnormalities. A proposed classification identifies three distinct categories of this syndrome: Type I (classic) is marked by prenatal growth deficiency becoming more severe after birth, moderate to profound psychomotor retardation, and severe malformations usually leading to disability or death; Type II (mild) is characterized by facial and skeletal abnormalities which are similar to those in Type I but are much less severe, moderate pre- and postnatal growth retardation, and the absence of major malformations; and Type III in which phenotypic manifestations are related to chromosomal aneuploidies or teratogenic factors. The syndrome was first observed in Amsterdam, hence its synonyms Amsterdam dwarf, Amsterdam type, and typus amstelodamensis. Manifestations of duplication of the long arm of chromosome 3 are similar to those in de Lange syndrome. Intrauterine growth retardation, prominent philtrum, proximally placed thumbs, oligodactyly, and phocomelia are more frequent in de Lange syndrome, while craniosynostosis, cleft palate, and urinary tract anomalies are more common in dup(3q). Most de Lange syndrome patients have normal chromosomes.
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