Cryptorchidism, or failure of testicular descent, is a common human congenital abnormality with a multifactorial etiology that likely reflects the involvement of endocrine, environmental, and hereditary factors. Cryptorchidism can result in infertility and increases risk for testicular tumors. Testicular descent from abdomen to scrotum occurs in 2 distinct phases: the transabdominal phase and the inguinoscrotal phase (summary by Gorlov et al., 2002).

Ventral, lateral, or ventrolateral bowing of the shaft and glans penis of more than 30 degrees.

Abnormal position of urethral meatus on the ventral penile shaft (underside) characterized by displacement of the urethral meatus from the tip of the glans penis to the ventral surface of the penis, scrotum, or perineum.

Webbing or fusion of the fingers or toes, involving soft parts only or including bone structure. Bony fusions are referred to as "bony" syndactyly if the fusion occurs in a radio-ulnar axis. Fusions of bones of the fingers or toes in a proximo-distal axis are referred to as "symphalangism".

A type of knee joint contracture in which the knee is in a fixed bent (flexed) configuration such that it cannot be straightened actively or passively.

An abnormal osseous union (fusion) between the radius and the humerus.

A soft tissue continuity in the A/P axis between two fingers that extends distally to at least the level of the proximal interphalangeal joints, or a soft tissue continuity in the A/P axis between two fingers that lies significantly distal to the flexion crease that overlies the metacarpophalangeal joint of the adjacent fingers.

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

A height below that which is expected according to age and gender norms. Although there is no universally accepted definition of short stature, many refer to "short stature" as height more than 2 standard deviations below the mean for age and gender (or below the 3rd percentile for age and gender dependent norms).

Failure to thrive (FTT) refers to a child whose physical growth is substantially below the norm.

Anterior malposition of the anus.

A type of hearing impairment in one or both ears related to an abnormal functionality of the cochlear nerve.

Median longitudinal ear length greater than two standard deviations above the mean and median ear width greater than two standard deviations above the mean (objective); or, apparent increase in length and width of the pinna (subjective).

Moderate mental retardation is defined as an intelligence quotient (IQ) in the range of 35-49.

The closed form of spina bifida with incomplete closure of a vertebral body with intact overlying skin.

The corpus callosum is the largest fiber tract in the central nervous system and the major interhemispheric fiber bundle in the brain. Formation of the corpus callosum begins as early as 6 weeks' gestation, with the first fibers crossing the midline at 11 to 12 weeks' gestation, and completion of the basic shape by age 18 to 20 weeks (Schell-Apacik et al., 2008). Agenesis of the corpus callosum (ACC) is one of the most frequent malformations in brain with a reported incidence ranging between 0.5 and 70 in 10,000 births. ACC is a clinically and genetically heterogeneous condition, which can be observed either as an isolated condition or as a manifestation in the context of a congenital syndrome (see MOLECULAR GENETICS and Dobyns, 1996). Also see mirror movements-1 and/or agenesis of the corpus callosum (MRMV1; 157600). Schell-Apacik et al. (2008) noted that there is confusion in the literature regarding radiologic terminology concerning partial absence of the corpus callosum, where various designations have been used, including hypogenesis, hypoplasia, partial agenesis, or dysgenesis.

Dysplasia and dysgenesis of the corpus callosum are nonspecific descriptions that imply defective development of the corpus callosum. The term dysplasia is applied when the morphology of the corpus callosum is altered as a congenital trait. For instance, the corpus callosum may be hump-shaped, kinked, or a striped corpus callosum that lacks an anatomically distinct genu and splenium.

Underdevelopment of the anterior pituitary gland.

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

Intellectual disability, previously referred to as mental retardation, is characterized by subnormal intellectual functioning that occurs during the developmental period. It is defined by an IQ score below 70.

Atrophy of the cortex of the cerebrum.

Protrusion of the contents of the abdominal cavity through the inguinal canal.

Developmental hypoplasia of the mandible.

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.

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

Absence of one half of the vertebral body.

Infants normally have two fontanels at birth, the diamond-shaped anterior fontanelle at the junction of the coronal and sagittal sutures, and the posterior fontanelle at the intersection of the occipital and parietal bones. The posterior fontanelle usually closes by the 8th week of life, and the anterior fontanel closes by the 18th month of life on average. This term applies if there is delay of closure of the fontanelles beyond the normal age.

An elbow contracture that limits the ability of the elbow joint to be extended (straightened), meaning that the elbow is fixed in an flexed (bent) position.

Increased width (cross-sectional diameter) of the clavicles.

In newborns, the two frontal bones, two parietal bones, and one occipital bone are joined by fibrous sutures, which form a small posterior fontanelle, and a larger, diamond-shaped anterior fontanelle. These regions allow for the skull to pass the birth canal and for later growth. The fontanelles gradually ossify, whereby the posterior fontanelle usually closes by eight weeks and the anterior fontanelle by the 9th to 16th month of age. Large fontanelles are diagnosed if the fontanelles are larger than age-dependent norms.

A decreased rate of skeletal maturation. Delayed skeletal maturation can be diagnosed on the basis of an estimation of the bone age from radiographs of specific bones in the human body.

Progressively increasing bone density of the skull base without significant changes in bony contour.

Tubulation refers to the size and shape of tubular bones. In children and adolescents, the modeling process regulates normal bone growth. Final shaft (tube) diameter depends on appositional bone growth and the equilibrium between periosteal and endosteal bone resorption and formation. Undertubulation refers to a broad, widened form of the shafts (diaphyses) of long bones.

The ability of the finger joints to move beyond their normal range of motion.

The capability that a joint (or a group of joints) has to move, passively and/or actively, beyond normal limits along physiological axes.

Increased width of ribs

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.

The presence of a splayed (i.e.,flared) metaphyseal segment of one or more long bones.

Generalized muscular hypotonia (abnormally low muscle tone).

The term proximal symphalangism refers to a bony fusion of the middle and proximal phalanges of the digits of the hand, in other words the proximal interphalangeal joint (PIJ) is missing which can be seen either on x-rays or as an absence of the proximal interphalangeal finger creases.

Head circumference below 2 standard deviations below the mean for age and gender.

Absence or abnormal closure of the choana (the posterior nasal aperture). Most embryologists believe that posterior choanal atresia results from a failure of rupture between the 35th and 38th day of fetal life of the partition which separates the bucconasal or buccopharyngeal membranes. The resultant choanal atresia may be unilateral or bilateral, bony or membranous, complete or incomplete. In over 90 per cent of cases the obstruction is bony, while in the remainder it is membranous. The bony type of atresia is commonly located 1-2 mm. anterior to the posterior edge of the hard palate, and the osseous septum varies in thickness from 1 to 10 mm. In the membranous form of choanal atresia the obstruction usually occurs further posteriorly. In approximately one third of cases the atresia is bilateral.

Developmental hypoplasia of the dental enamel.

Decreased length and width of the tongue.

Narrowing of a tear duct (lacrimal duct).

Any abnormality of the teeth.

Abnormal prominence of the chin related to increased length of the mandible.

Abnormal narrowing of the choana (the posterior nasal aperture).

Forward prominence of the entire forehead, due to protrusion of the frontal bone.

Width of the forehead or distance between the frontotemporales is more than two standard deviations above the mean (objective); or apparently increased distance between the two sides of the forehead.

Cleft palate is a developmental defect of the palate resulting from a failure of fusion of the palatine processes and manifesting as a separation of the roof of the mouth (soft and hard palate).

Wrinkled, redundant, inelastic and sagging skin.

A reticular discoloration of the skin with cyanotic (reddish-blue appearing) areas surrounding pale central areas due to dilation of capillary blood vessels and stagnation of blood within the vessels. Cutis marmorata generally occurs on the legs, arms and trunk and is often more severe in cold weather.

Reduction in thickness of the skin, generally associated with a loss of suppleness and elasticity of the skin.

Reduced density of hairs.

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).