- Atypical behavior (HP:0000708): Atypical behavior is an abnormality in a person's actions that can be controlled or modulated by the will of the individual. While abnormal behaviors can be difficult to control, they are distinct from other abnormal actions that cannot be affected by the individual's will. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:177910)
- Global developmental delay (HP:0001263): 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. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:177910)
- Neonatal hypotonia (HP:0001319): Muscular hypotonia (abnormally low muscle tone) manifesting in the neonatal period. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:177910)
- Obesity (HP:0001513): Accumulation of substantial excess body fat. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:177910)
- Decreased fetal movement (HP:0001558): An abnormal reduction in quantity or strength of fetal movements. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:177910)
- Short foot (HP:0001773): A measured foot length that is more than 2 SD below the mean for a newborn of 27 - 41 weeks gestation, or foot that is less than the 3rd centile for individuals from birth to 16 years of age (objective). Alternatively, a foot that appears disproportionately short (subjective). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:177910)
- Abnormal facial shape (HP:0001999): An abnormal morphology (form) of the face or its components. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:177910)
- Polyphagia (HP:0002591): A neurological anomaly with gross overeating associated with an abnormally strong desire or need to eat. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:177910)
- Short stature (HP:0004322): 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). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:177910)
- Feeding difficulties in infancy (HP:0008872): Impaired feeding performance of an infant as manifested by difficulties such as weak and ineffective sucking, brief bursts of sucking, and falling asleep during sucking. There may be difficulties with chewing or maintaining attention. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:177910)
- Small hand (HP:0200055): Disproportionately small hand. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:177910)
- Abnormal ulnar metaphysis morphology (HP:0004039): Any structural abnormality of the portion of the ulna between the epiphysis and the diaphysis. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:177910)
- Narrow palm (HP:0004283): For children from birth to 4 years of age, the palm width is more than 2 SD below the mean; for children from 4 to 16 years of age the palm width is below the 5th centile; or, the width of the palm appears disproportionately narrow for its length. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:177910)
- Hypogonadotropic hypogonadism (HP:0000044): Hypogonadotropic hypogonadism is characterized by reduced function of the gonads (testes in males or ovaries in females) and results from the absence of the gonadal stimulating pituitary hormones: follicle stimulating hormone (FSH) and luteinizing hormone (LH). Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:177910)
- Hypopigmentation of the skin (HP:0001010): A reduction of skin color related to a decrease in melanin production and deposition. Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:177910)
- External genital hypoplasia (HP:0003241): Underdevelopment of part or all of the external reproductive organs. Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:177910)
- Hypopigmentation of hair (HP:0005599). Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:177910)
- Iris hypopigmentation (HP:0007730): An abnormal reduction in the amount of pigmentation of the iris. Evidence: TAS. Frequency: Very rare (HP:0040284). (ORPHA:177910)
These phenotypes are associated with the disease Prader-Willi syndrome due to imprinting mutation (ORPHA:177910).