A foot where the longitudinal arch of the foot is in contact with the ground or floor when the individual is standing; or, in a patient lying supine, a foot where the arch is in contact with the surface of a flat board pressed against the sole of the foot by the examiner with a pressure similar to that expected from weight bearing; or, the height of the arch is reduced.

An abnormality of the mitral valve characterized by insufficiency or incompetence of the mitral valve resulting in retrograde leaking of blood through the mitral valve upon ventricular contraction.

An aneurysm (severe localized balloon-like outward bulging) in the pulmonary artery.

Aortic dissection refers to a tear in the intimal layer of the aorta causing a separation between the intima and the medial layers of the aorta.

The presence of a localized dilatation or ballooning of a cerebral artery.

An increase in size of the ventricular system of the brain.

Displacement or malalignment of joints.

Bilateral bulging of the lateral frontal bone prominences with relative sparing of the midline.

A flexion contracture is a bent (flexed) joint that cannot be straightened actively or passively. It is thus a chronic loss of joint motion due to structural changes in muscle, tendons, ligaments, or skin that prevents normal movement of joints.

An abnormal lack of stability of the cervical spine.

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.

The ability of a joint to move beyond its normal range of motion.

A relatively mild degree of macrocephaly in which the head circumference is not above two standard deviations from the mean, but appears dysproportionately large when other factors such as body stature are taken into account.

Underdevelopment of the malar prominence of the jugal bone (zygomatic bone in mammals), appreciated in profile, frontal view, and/or by palpation.

An anomaly of the sternum, also known as the breastbone.

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

Uvula separated into two parts most easily seen at the tip.

An eye that is protruding anterior to the plane of the face to a greater extent than is typical.

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).