The 47, XYY syndrome was first described in 1961 [9]. Since then, many cases have been reported, mostly in late childhood, adolescence, and adulthood. The reason for delayed detection is a lack of specific dysmorphic signs. Mental disability varies from case to case, ranging from normal to an IQ of 70. Most cases were evaluated because of specific behavioral problems at school, or later in life, because of tall stature beyond their target height [10]. Moreover, larger craniofacial dimensions than normal (vault, facial height, chin) can raise suspicion for this syndrome. Ellis et al. [11] suggested the important role of Y-specific growth genes, which promote growth in 47, XYY individuals.
Urogenital malformations causing olygohydramnios and, consequently Potter sequence (microbrachycephaly, flat face, wide-spaced eyes, large and poorly developed ears, abnormal positioning of hands and feet, pulmonary hypoplasia) are reported to be more frequent than normal [12]. It has been suggested that newborns having Potter sequence of unknown origin should be checked for the 47,XYY karyotype.
Many minor features described in the literature were present in our patient. The presence of minor dysmorphic features in our case, although non specific, is described in different cases in the literature. The difficulty of regular detection of this syndrome is mentioned by many authors due to the different combination of signs. Many cases were detected by chance. However, a combination of mental retardation and stature higher than predicted, can raise the suspicion for the syndrome.
Most XYY individuals have borderline intelligence, while some are mildly retarded. A higher degree of mental retardation is associated with a higher number of behavioral problems [13]. Adequate specialist training and counseling of the family could provide sufficient control of the antisocial behavior.
A relationship between autistic and violent behavior and XYY syndrome is still controversial. The frequent presence of persons with XYY syndrome in prisons and correctional institutions associates this chromosomal disorder with violent behavior. About 1% of male prisoners have the XYY karyotype, an incidence higher than that found in the newborn population [14]. However, these prisoners are reported to commit mainly misdemeanors such as theft, fighting, burglary, drug abuse and only rarely serious crimes such as murder [15]. Other psychiatric disorders such as pervasive developmental disorders [16], autism [17], and schizophrenia [18] have been described. The biochemical effects of the double dosage of gene products on the Y chromosome on the behavioral and psychiatric disorders is still unknown [19], but the extra Y chromosome may be related to abnormal brain development [16]. The question of whether such individuals should be declared not guilty for medical reasons in criminal proceedings is still unsolved [15].
Our patient had some degree of aggressive behavior. However, it is difficult to attribute it to the XYY phenotype since his father was also prone to violent behavior.
This syndrome has been referred in association with fragile X syndrome [20], congenital heart disease [4], Prader-Willi syndrome [21], and myotonic dystrophy [22]. Such associations appear to be coincidental, and do not depend on presence of the XYY chromosome complement.
Unlike other trisomies, where the abnormality occurs during maternal meiosis I, in XYY syndrome, the error occurs during paternal meiosis [23]. In most cases, the non-disjunction occurs during paternal meiosis II, but in some it occurs during the first mitotic divisions in the embryo [24].
Conventional cytogenetics is a standard method for detection of the chromosomal abnormality. The FISH analysis with a fluorochrome-labeled, chromosome-specific DNA probe, is also used as a complementary technique to detect the origin of the marker chromosome, to detect low rate mosaicism in a large number of cells, as well as XX and XY disomy in spermia during in vitro fertilization procedures, as it is impossible to detect aneu­ploidy in non-dividing cells with conventional karyo­typing [5].
The XYY individuals have normal genitalia and normal sexual development, except in some cases where cryptorchidism and hypospadias have been described [7]. However, hypospermia and infertility have been reported [25,26]. The 47, XYY individuals frequently have normal offspring, since the extra Y chromosomes in the disomic spermatozoa have usually been lost during spermato­genesis, mostly in pachytene during meiosis 1, and in the remaining disomic spermatogonia, during postreductional divisions [6,27]. Many studies reported a wide range for the percentage of disomic sperm in XYY individuals, varying from 0.3% [28] to15% [29], but most of them average around 1% [5,30]. Their offspring have slightly increased risk for gonosomal and autosomal aneuploidy than average and should be examined.
Follow-up of XYY children will provide information for assessment of their quality of life and of their fertility rate. Since 47, XYY is detected more frequently prenatally, this information would help future parents in making the decision of whether to terminate the pregnancy. It is worth noting that the rate of pregnancy termination of these fetuses is steadily declining [31-33].