Severe distention of the kidney with dilation of the renal pelvis and calices.

A connection of the right and left kidney by an isthmus of functioning renal parenchyma or fibrous tissue that crosses the midline.

Abnormally long and slender fingers ("spider fingers").

In utero, the ductus arteriosus (DA) serves to divert ventricular output away from the lungs and toward the placenta by connecting the main pulmonary artery to the descending aorta. A patent ductus arteriosus (PDA) in the first 3 days of life is a physiologic shunt in healthy term and preterm newborn infants, and normally is substantially closed within about 24 hours after bith and completely closed after about three weeks. Failure of physiologcal closure is referred to a persistent or patent ductus arteriosus (PDA). Depending on the degree of left-to-right shunting, PDA can have clinical consequences.

Atrial septal defect (ASD) is a congenital abnormality of the interatrial septum that enables blood flow between the left and right atria via the interatrial septum.

Underdevelopment of the arch of aorta.

An abnormal restriction of fetal growth with fetal weight below the tenth percentile for gestational age.

Upper insertion of the ear to the scalp below an imaginary horizontal line drawn between the inner canthi of the eye and extending posteriorly to the ear.

Laterally protruding ear that lacks antihelical folding (including absence of inferior and superior crura).

Hydrocephalus is an active distension of the ventricular system of the brain resulting from inadequate passage of CSF from its point of production within the cerebral ventricles to its point of absorption into the systemic circulation.

Dilated, glial-lined cavity in spinal cord. This cavity does not communicate with the central canal, and usually is between the dorsal columns unilaterally or bilaterally along the side of the cord.

A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age.

Dandy-Walker malformation is defined by hypoplasia and upward rotation of the cerebellar vermis and cystic dilation of the fourth ventricle. Affected individuals often have motor deficits such as delayed motor development, hypotonia, and ataxia; about half have mental retardation and some have hydrocephalus. DWM is a heterogeneous disorder. The low empiric recurrence risk of approximately 1 to 2% for nonsyndromic DWM suggests that mendelian inheritance is unlikely (summary by Murray et al., 1985).

Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist.

An abnormal curvature of the spine in both a coronal (lateral) and sagittal (back-to-front) plane.

The distal interphalangeal joint and/or the proximal interphalangeal joint of the fingers or toes cannot be extended to 180 degrees by either active or passive extension.

A form of developmental hypoplasia of the mandible in which the mandible is mislocalised posteriorly.

Height of the palate more than 2 SD above the mean (objective) or palatal height at the level of the first permanent molar more than twice the height of the teeth (subjective).

The palpebral fissure inclination is more than two standard deviations below the mean.

Although hypertelorism means an excessive distance between any paired organs (e.g., the nipples), the use of the word has come to be confined to ocular hypertelorism. Hypertelorism occurs as an isolated feature and is also a feature of many syndromes, e.g., Opitz G syndrome (see 300000), Greig cephalopolysyndactyly (175700), and Noonan syndrome (163950) (summary by Cohen et al., 1995).