All the following are features of Down's syndrome except –
Clinical features of Down's syndrome

A most striking feature in the neonate is hypotonia and although the diagnosis is usually evident at this time, it may sometimes be missed if the baby is very premature or his facial features are concealed by ventilatory apparatus.

CLINICAL FEATURES IN DOWN SYNDROME

General

Neonatal hypotonia
Mild-moderate mental retardation
Short Stature

Cranio-facial

Brachycephaly
Clinodactyly
Epicanthic folds
Protruding tongue
Small ears
Upward sloping palpebral fissures
Strabismus and/or nystagmus
Brushfield spots in the iris

Increased incidence of leukaemia (1%)
Limbs

Fifth finger clinodactyly
Single palmar crease (simian crease)
The wide gap between first and second toes

Other

Congenital heart disease (40%) e.g. common atrioventricular canal, ASD, PDA, VSD, Fallot tetralogy
Anal atresia & Hirschsprung disease
Duodenal atresia & annular pancreas
Hypothyroidism & DM
Delayed fontanel closure
Three fontanel
Obesity & obstructive sleep apnea
Brushfield's spots in iris
Simian crease
Mental retardation
Hypertonicity