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).

Congenital absence of the anus, i.e., the opening at the bottom end of the intestinal tract.

A decreased magnitude of the sensory perception of sound.

A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.

An abnormal pattern in the quality, quantity, or characteristics of sleep.

A degree of language development that is significantly below the norm for a child of a specified age.

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.

Persistent deficits in social interaction and communication and interaction as well as a markedly restricted repertoire of activity and interest as well as repetitive patterns of behavior.

Attention-deficit/hyperactivity disorder (ADHD) is a behavioral disorder that typically begins in childhood and is characterized by a short attention span (inattention), an inability to be calm and stay still (hyperactivity), and poor impulse control (impulsivity). Some people with ADHD have problems with only inattention or with hyperactivity and impulsivity, but most have problems related to all three features.\n\nIn people with ADHD, the characteristic behaviors are frequent and severe enough to interfere with the activities of daily living such as school, work, and relationships with others. Because of an inability to stay focused on tasks, people with inattention may be easily distracted, forgetful, avoid tasks that require sustained attention, have difficulty organizing tasks, or frequently lose items.\n\nHyperactivity is usually shown by frequent movement. Individuals with this feature often fidget or tap their foot when seated, leave their seat when it is inappropriate to do so (such as in the classroom), or talk a lot and interrupt others.\n\nIn most affected individuals, ADHD continues throughout life, but in about one-third of individuals, signs and symptoms of ADHD go away by adulthood.\n\nImpulsivity can result in hasty actions without thought for the consequences. Individuals with poor impulse control may have difficulty waiting for their turn, deferring to others, or considering their actions before acting.\n\nMore than two-thirds of all individuals with ADHD have additional conditions, including insomnia, mood or anxiety disorders, learning disorders, or substance use disorders. Affected individuals may also have autism spectrum disorder, which is characterized by impaired communication and social interaction, or Tourette syndrome, which is a disorder characterized by repetitive and involuntary movements or noises called tics.

A type of motor delay characterized by a delay in acquiring the ability to control the large muscles of the body for walking, running, sitting, and crawling.

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.

A type of motor delay characterized by a delay in acquiring the ability to control the fingers and hands.

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.

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

Occipitofrontal (head) circumference greater than 97th centile compared to appropriate, age matched, sex-matched normal standards. Alternatively, a apparently increased size of the cranium.

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

Increased susceptibility to otitis media, as manifested by recurrent episodes of otitis media.

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

Facial contour, as viewed from the front, triangular in shape, with breadth at the temples and tapering to a narrow chin.

Height of the vermilion of the upper lip in the midline more than 2 SD below the mean. Alternatively, an apparently reduced height of the vermilion of the upper lip in the frontal view (subjective).

The onset of secondary sexual characteristics before a normal age. Although it is difficult to define normal age ranges because of the marked variation with which puberty begins in normal children, precocious puberty can be defined as the onset of puberty before the age of 8 years in girls or 9 years in boys.

Presence of more than two nipples.