1. Background

• XXX Syndrome is the most frequent X chromosomal anomaly in females
• first described by P.A. Jacobs, Lancet 2:423 (1959).
• also called Chromosome X, Triplo-X and Chromsome 47, XXX karyotype

2. Pathogenesis

• due to parental meiotic nondisjunction (usually maternal)
• the XXX Syndrome phenotype is quite variable

1. Dysmorphisms

• hypertelorism
• tall stature (average height 172 cm)
• widely-spaced nipples
• webbed neck

2. Neurological Manifestations

• variable IQ from superior to moderate-to-severe mental retardation
• transient gross motor delays
• speech and language delays
• fine motor delays
  • coordination problems with awkwardness
• behavioural problems
  • mild depression, conduct disorder, immature behaviour, socializing problems
• occasionally seizures

3. Endocrine Manifestations

• normal sexual development and menarche
• may be some fertility problems
• Mullerian anomalies

1. Karyotype

• 47, XXX karyotype

2. CT (Head)

• occasionally mild ventricular enlargement

1. Supportive

• Paediatrics, Endocrinology, Neurology, Psychology
• genetic counselling - no XXX daughter of an XXX mother has been reported

2. Prognosis

• normal life span
• may need supplemental teaching for poor academic performance

1. Jones, K.L., Smith's Recognizable Patterns of Human Malformation (5th Edition). p. 78-79. (1997).

2. Baraitser, M. and R.M. Winter, Color Atlas of Congenital Malformation Syndromes (1st Edition). p. 11. (1996).