- Short philtrum (HP:0000322): Distance between nasal base and midline upper lip vermilion border more than 2 SD below the mean. Alternatively, an apparently decreased distance between nasal base and midline upper lip vermilion border. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1598)
- Protruding ear (HP:0000411): Angle formed by the plane of the ear and the mastoid bone greater than the 97th centile for age (objective); or, outer edge of the helix more than 2 cm from the mastoid at the point of maximum distance (objective). Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1598)
- Hypodontia (HP:0000668): The absence of five or less teeth from the normal series by a failure to develop. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1598)
- Delayed speech and language development (HP:0000750): A degree of language development that is significantly below the norm for a child of a specified age. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1598)
- Brachydactyly (HP:0001156): Digits that appear disproportionately short compared to the hand/foot. The word brachydactyly is used here to describe a series distinct patterns of shortened digits (brachydactyly types A-E). This is the sense used here. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1598)
- Intellectual disability (HP:0001249): The term intellectual disability or intellectual developmental disorder is used to describe significantly sub-average intellectual and adaptive functioning based on clinical assessment and as measured by individually administered, appropriately normed, standardized and validated tests of intellectual functioning and adaptive behavior, with onset during the developmental period from infancy through adolescence. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1598)
- 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: Very frequent (HP:0040281). (ORPHA:1598)
- 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: Very frequent (HP:0040281). (ORPHA:1598)
- Abnormal antihelix morphology (HP:0009738): An abnormality of the antihelix. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:1598)
- Cleft palate (HP:0000175): 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). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Brachycephaly (HP:0000248): An abnormality of skull shape characterized by a decreased anterior-posterior diameter. That is, a cephalic index greater than 81%. Alternatively, an apparently shortened anteroposterior dimension (length) of the head compared to width. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Microcephaly (HP:0000252): Head circumference below 2 standard deviations below the mean for age and gender. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Epicanthus (HP:0000286): A fold of skin starting above the medial aspect of the upper eyelid and arching downward to cover, pass in front of and lateral to the medial canthus. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Micrognathia (HP:0000347): Developmental hypoplasia of the mandible. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Macrotia (HP:0000400): 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). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Wide nasal bridge (HP:0000431): Increased breadth of the nasal bridge (and with it, the nasal root). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Webbed neck (HP:0000465): Pterygium colli is a congenital skin fold that runs along the sides of the neck down to the shoulders. It involves an ectopic fibrotic facial band superficial to the trapezius muscle. Excess hair-bearing skin is also present and extends down the cervical region well beyond the normal hairline. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Short neck (HP:0000470): Diminished length of the neck. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Ptosis (HP:0000508): The upper eyelid margin is positioned 3 mm or more lower than usual and covers the superior portion of the iris (objective); or, the upper lid margin obscures at least part of the pupil (subjective). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Carious teeth (HP:0000670): Caries is a multifactorial bacterial infection affecting the structure of the tooth. This term has been used to describe the presence of more than expected dental caries. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Tooth malposition (HP:0000692): Abnormal alignment, positioning, or spacing of the teeth, i.e., misaligned teeth. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Pectus excavatum (HP:0000767): A defect of the chest wall characterized by a depression of the sternum, giving the chest ("pectus") a caved-in ("excavatum") appearance. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Hypertension (HP:0000822): The presence of chronic increased pressure in the systemic arterial system. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Hypotonia (HP:0001252): 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. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Low posterior hairline (HP:0002162): Hair on the neck extends more inferiorly than usual. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Downturned corners of mouth (HP:0002714): A morphological abnormality of the mouth in which the angle of the mouth is downturned. The oral commissures are positioned inferior to the midline labial fissure. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Kyphoscoliosis (HP:0002751): An abnormal curvature of the spine in both a coronal (lateral) and sagittal (back-to-front) plane. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Wide intermamillary distance (HP:0006610): A larger than usual distance between the left and right nipple. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Enlarged thorax (HP:0100625). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:1598)
- Microphthalmia (HP:0000568): A developmental anomaly characterized by abnormal smallness of one or both eyes. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:1598)
- 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: Occasional (HP:0040283). (ORPHA:1598)
- Hypothyroidism (HP:0000821): Deficiency of thyroid hormone. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:1598)
- Lymphedema (HP:0001004): Localized fluid retention and tissue swelling caused by a compromised lymphatic system. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:1598)
- Holoprosencephaly (HP:0001360): Holoprosencephaly is a structural anomaly of the brain in which the developing forebrain fails to divide into two separate hemispheres and ventricles. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:1598)
- Alopecia (HP:0001596): A noncongenital process of hair loss, which may progress to partial or complete baldness. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:1598)
- Autoimmunity (HP:0002960): The occurrence of an immune reaction against the organism's own cells or tissues. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:1598)
- Generalized dystonia (HP:0007325): A type of dystonia that affects all or most of the body. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:1598)
- Abnormal cardiovascular system morphology (HP:0030680): Any structural anomaly of the heart and blood vessels. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:1598)
These phenotypes are associated with the disease Monosomy 18p syndrome (ORPHA:1598).