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).

Abnormally small penis. At birth, the normal penis is about 3 cm (stretched length from pubic tubercle to tip of penis) with micropenis less than 2.0-2.5 cm.

An abnormal shortening of the femur.

Underdevelopment of the fibula.

Underdevelopment (reduced size) of the tibia.

Underdevelopment of the ulna.

A small/hypoplastic or absent/aplastic radius.

Absent thumb, i.e., the absence of both phalanges of a thumb and the associated soft tissues.

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).

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.

The presence of more than 12 rib pairs.

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.

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

Distance between the commissures of the mouth more than 2 SD below the mean. Alternatively, an apparently decreased width of the oral aperture (subjective).

Height of the vermilion of the medial part of the lip more than 2 SD below the mean, or apparently reduced height of the vermilion of the lip in the frontal view. The vermilion is the red part of the lips (and confusingly, the vermilion itself is also often referred to as being equivalent the lips).

A misalignment of the eyes so that the visual axes deviate from bifoveal fixation. The classification of strabismus may be based on a number of features including the relative position of the eyes, whether the deviation is latent or manifest, intermittent or constant, concomitant or otherwise and according to the age of onset and the relevance of any associated refractive error.