Sir.—The fragile X syndrome is the most common form of inherited mental retardation occurring in approximately one per 1000 live births.1 The disorder is manifested not only by mental retardation or learning disabilities but also by the clearly defined physical characteristics that include large, prominent ears; joint laxity; macro-orchidism; puffiness around the eyes; broad palpebral fissures; and a long, narrow face. There are also cognitive, behavioral, and temperamental characteristics associated with the syndrome.2 Autistic features are common, including poor eye contact, perseveration in speech and behavior, and tactile defensiveness, suggesting an increased sensitivity to a variety of stimuli.3 There is also an aberrant approach-withdrawal behavioral pattern in social interactions.4 Among the most common physical findings in these individuals is hypotonia and hyperextensibility of the joints, suggesting a connective tissue dysplasia in fragile X syndrome.2,5 Prolapse of the mitral valve is seen frequently, and the
GOLDSON E, HAGERMAN RJ. Fragile X Syndrome and Failure to Thrive. Am J Dis Child. 1993;147(6):605–607. doi:10.1001/archpedi.1993.02160300011002
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