Clinical features Down's syndrome is usually suspected at birth because of the baby's facial appearance

Typical craniofacial appearance 1. Round face and flat nasal bridge 2. Upslanted palpebral fissures 3. Epicanthic folds (a fold of skin running across the inner edge of the palpebral fissure) 4. Brushfield spots in iris (pigmented spots) 5. Small mouth and protruding tongue Small ears 6. Flat occiput and third fontanelle

Other anomalies 1. Short neck 2. Single palmar creases, incurved fifth finger and wide 'sandal' gap between toes 3. Hypotonia 4. Congenital heart defects (40%) 5. Duodenal atresia 6. Hirschsprung's disease

Later medical problems 1. Delayed motor milestones 2. Moderate to severe learning difficulties Small stature 3. Increased susceptibility to infections 4. Hearing impairment from secretory otitis media 5. Visual impairment from cataracts, squints, myopia 6. Increased risk of leukaemia and solid tumours 7. Risk of atlantoaxial instability 8. Hypothyroidism and coeliac disease 9. Epilepsy 10. Alzheimer's disease

Edwards' syndrome (trisomy 18) and Patau's syndrome (trisomy 13) Although rarer than Down's syndrome (1 in 8000 and 1 in 14 000 live births, respectively), particular constellations of severe multiple abnormalities suggest the diagnosis at birth and most affected babies die in infancy The diagnosis is confirmed by chromosome analysis

Clinical features of Edwards' syndrome (trisomy 18) Low birthweight Prominent occiput Small mouth and chin Short sternum Flexed, overlapping fingers Rocker-bottom feet Cardiac and renal malformations

Clinical features of Patau's syndrome (trisomy 13) Structural defect of brain Scalp defects Small eyes (microphthalmia) and other eye defects Cleft lip and palate Polydactyly Cardiac and renal malformations

Turner's syndrome (45, X) Usually (>95%) this results in early miscarriage. In live-born females, the incidence is about 1 in 2500 short stature may be the only clinical abnormality in children.

Clinical features of Turner's syndrome Lymphoedema of hands and feet in neonate, which may persist Short stature - cardinal feature Neck webbing or thick neck Wide carrying angle (cubitus valgus) Widely spaced nipples Congenital heart defects (particularly coarctation of the aorta) Delayed puberty

Ovarian dysgenesis resulting in infertility, although pregnancy may be possible with in-vitro fertilisation (IVF) with donated ova Hypothyroidism Renal anomalies Pigmented moles Recurrent otitis media Normal intellectual function in most

Treatment 1. growth hormone therapy 2. oestrogen replacement for development of secondary sexual characteristics at the time of puberty (but infertility persists).

Klinefelter's syndrome (47, XXY) 1.Infertility - most common presentation 2. Hypogonadism with small testes 3. Pubertal development apparently normal (some males benefit from testosterone therapy) 4. Gynaecomastia in adolescence 5. Tall stature 6. Intelligence - usually in the normal range, but may have educational and psychological problems