Klinefelter (47,XXY) syndrome (KS), the most common form of sex-chromosomal aneuploidy, is characterized by physical, endocrinologic, and reproductive abnormalities. Individuals with KS also exhibit a cognitive/behavioral phenotype characterized by language and language-based learning disabilities and executive and attentional dysfunction in the…

Objective: The goal of this study was to contrast the cognitive phenotypes in boys with 47,XYY (XYY) karyotype and boys with 47,XXY karyotype [Klinefelter syndrome, (KS)], who share an extra copy of the X-Y pseudoautosomal region but differ in their dosage of strictly sex-linked genes. Methods: Neuropsychological evaluation of general cognitive…

Variation in the number of sex chromosomes is a relatively common genetic condition, affecting as many as 1/400 individuals. The sex chromosome aneuploidies (SCAs) are associated with characteristic behavioral and cognitive phenotypes, although the degree to which specific individuals are affected can fall within a wide range. Understanding the…

Klinefelter syndrome (47,XXY) was initially described in the context of its endocrinologic and physical features; however, subsequent studies have revealed specific impairments in verbal skills and social functioning. Males with sex chromosomal aneuploidies are known to have variability in their developmental profile with the majority presenting…

Fragile X syndrome (FXS), a single gene disorder with an expanded CGG allele on the X chromosome, is the most common form of inherited cognitive impairment. The cognitive deficit ranges from mild learning disabilities to severe intellectual disability. The phenotype includes hyperactivity, short attention span, emotional problems including…

Fragile X syndrome (FraX) remains the most common inherited cause of intellectual disability and provides a valuable model for studying gene-brain-behavior relationships. Over the past 15 years, structural and functional magnetic resonance imaging studies have emerged with the goal of better understanding the neural pathways contributing to the…

Research into the determinants and developmental course of fragile X syndrome (FXS) has made remarkable progress over the last 25 years. However, treatments to ameliorate the symptoms of FXS have been less forthcoming. While there is optimism in the field that the pace of intervention research is quickening, there has been a bias toward…

X-linked intellectual disability (XLID) accounts for approximately 16% of males with intellectual disability (ID). This is, in part, related to the fact that males have a single X chromosome. Progress in the clinical and molecular characterization of XLID has outpaced progress in the delineation of ID due to genes on the other 22 chromosomes.…

Memorizing the basic number combinations, such as 9 + 7 = 16 and 16 - 9 = 7, is a punishing and insurmountable task for children with difficulties learning mathematics. Two perspectives on such learning lead to different conclusions about the primary source of this key learning difficulty. According to the conventional wisdom (the Passive Storage…

According to the American Psychiatric Association [DSM-IV-TR, 2000], Attention-Deficit Hyperactivity Disorder (ADHD) affects approximately 3-7% of the school aged population and 2-4% of the adult population. Recently, college students with ADHD have begun to receive more attention, largely due to the increase in numbers of high school students…

This article extends previous reviews regarding the peer problems of children with Attention Deficit Hyperactivity Disorder (ADHD) in several ways. In addition to summarizing past and current literature regarding the social behaviors of children with ADHD, these behaviors are discussed in terms of subtype and gender differences and treatment…

Although children with Attention-Deficit Hyperactivity Disorder (ADHD) exhibit significant academic difficulties in school settings, considerably less attention is devoted to remediating their academic problems when compared to behavioral and social difficulties. The purpose of this article is to review empirically supported academic interventions…

Velo-cardio-facial syndrome is one of the names that has been attached to one of the most common multiple anomaly syndromes in humans. The labels DiGeorge sequence, 22q11 deletion syndrome, conotruncal anomalies face syndrome, CATCH 22, and Sedlackova syndrome have all been attached to the same disorder. Velo-cardio-facial syndrome has an…

Several recurrent, constitutional genomic disorders are present on chromosome 22q. These include the translocations and deletions associated with DiGeorge and velocardiofacial syndrome and the translocations that give rise to the recurrent t(11;22) supernumerary der(22) syndrome (Emanuel syndrome). The rearrangement breakpoints on 22q cluster…

Velo-cardio-facial syndrome/DiGeorge syndrome (VCFS/DGS), the most common micro-deletion disorder in humans, is characterized by craniofacial, parathyroid, and thymic defects as well as cardiac outflow tract malformations. Most patients have a similar hemizygous 3 million base pair deletion on 22q11.2. Studies in mouse have shown that "Tbx1", a…