- 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:412069)
- 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:412069)
- 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: Very frequent (HP:0040281). (ORPHA:412069)
- 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:412069)
- Motor delay (HP:0001270): A type of Developmental delay characterized by a delay in acquiring motor skills. Evidence: TAS. Frequency: Very frequent (HP:0040281). (ORPHA:412069)
- Strabismus (HP:0000486): 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. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:412069)
- Abnormality of the vertebral column (HP:0000925): Any abnormality of the vertebral column. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:412069)
- Seizure (HP:0001250): 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. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:412069)
- Ataxia (HP:0001251): Ataxia refers to impaired coordination of voluntary muscle movement. Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- or overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly). Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:412069)
- Abnormal corpus callosum morphology (HP:0001273): Abnormality of the corpus callosum. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:412069)
- Joint hypermobility (HP:0001382): The capability that a joint (or a group of joints) has to move, passively and/or actively, beyond normal limits along physiological axes. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:412069)
- Failure to thrive (HP:0001508): Failure to thrive (FTT) refers to a child whose physical growth is substantially below the norm. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:412069)
- Abnormal facial shape (HP:0001999): An abnormal morphology (form) of the face or its components. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:412069)
- Expressive language delay (HP:0002474): A delay in the acquisition of the ability to use language to communicate needs, wishes, or thoughts. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:412069)
- Upper airway obstruction (HP:0002781): Increased resistance to the passage of air in the upper airway. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:412069)
- Obstructive sleep apnea (HP:0002870): Obstructive Sleep Apnea is a condition characterized by the obstruction of the airway and pauses in breathing during sleep, which occur multiple times throughout the night. It is related to the relaxation of muscle tone that typically happens during sleep, leading to a partial collapse of the soft tissues in the airway and causing airflow obstruction. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:412069)
- Upbeat nystagmus (HP:0011477): In primary position, the eyes drift slowly downward and then spontaneously beat upward. Upward gaze accentuates the nystagmus. The associated oscillopsias are often very irritating, but the symptoms are usually transient. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:412069)
- Feeding difficulties (HP:0011968): Impaired ability to eat related to problems gathering food and getting ready to suck, chew, or swallow it. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:412069)
- Abnormal brain morphology (HP:0012443): A structural abnormality of the brain, which has as its parts the forebrain, midbrain, and hindbrain. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:412069)
- Delayed ability to walk (HP:0031936): A failure to achieve the ability to walk at an appropriate developmental stage. Most children learn to walk in a series of stages, and learn to walk short distances independently between 12 and 15 months. Evidence: TAS. Frequency: Frequent (HP:0040282). (ORPHA:412069)
- Hypertelorism (HP:0000316): Interpupillary distance more than 2 SD above the mean (alternatively, the appearance of an increased interpupillary distance or widely spaced eyes). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Micrognathia (HP:0000347): Developmental hypoplasia of the mandible. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Hearing impairment (HP:0000365): A decreased magnitude of the sensory perception of sound. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Low-set ears (HP:0000369): Upper insertion of the ear to the scalp below an imaginary horizontal line drawn between the inner canthi of the eye and extending posteriorly to the ear. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Small earlobe (HP:0000385): Reduced volume of the earlobe. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- 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: Occasional (HP:0040283). (ORPHA:412069)
- Deeply set eye (HP:0000490): An eye that is more deeply recessed into the plane of the face than is typical. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Downslanted palpebral fissures (HP:0000494): The palpebral fissure inclination is more than two standard deviations below the mean. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Esotropia (HP:0000565): A form of strabismus with one or both eyes turned inward ('crossed') to a relatively severe degree, usually defined as 10 diopters or more. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Upslanted palpebral fissure (HP:0000582): The palpebral fissure inclination is more than two standard deviations above the mean for age (objective); or, the inclination of the palpebral fissure is greater than typical for age. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Autism (HP:0000717): Autism is a neurodevelopmental disorder characterized by impaired social interaction and communication, and by restricted and repetitive behavior. Autism begins in childhood. It is marked by the presence of markedly abnormal or impaired development in social interaction and communication and a markedly restricted repertoire of activity and interest. Manifestations of the disorder vary greatly depending on the developmental level and chronological age of the individual (DSM-IV). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Craniosynostosis (HP:0001363): Craniosynostosis refers to the premature closure of the cranial sutures. Primary craniosynostosis refers to the closure of one or more sutures due to abnormalities in skull development, and secondary craniosynostosis results from failure of brain growth. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Laryngomalacia (HP:0001601): Laryngomalacia is a congenital abnormality of the laryngeal cartilage in which the cartilage is floppy and prolapses over the larynx during inspiration. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Hypoplasia of the corpus callosum (HP:0002079): Underdevelopment of the corpus callosum. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- EEG abnormality (HP:0002353): Abnormality observed by electroencephalogram (EEG), which is used to record of the brain's spontaneous electrical activity from multiple electrodes placed on the scalp. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Scoliosis (HP:0002650): The presence of an abnormal lateral curvature of the spine. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Tracheomalacia (HP:0002779). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Respiratory failure requiring assisted ventilation (HP:0004887): A state of respiratory distress that requires a life saving intervention in the form of gaining airway access and instituting positive pressure ventilation. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Depressed nasal bridge (HP:0005280): Posterior positioning of the nasal root in relation to the overall facial profile for age. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Retrocerebellar cyst (HP:0006951). Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Uplifted earlobe (HP:0009909): An abnormal orientation of the earlobes such that they point out- and upward. That is, the lateral surface of ear lobe faces superiorly. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Delayed myelination (HP:0012448): Delayed myelination. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Snoring (HP:0025267): Deep, noisy breathing during sleep, accompanied by hoarse or harsh sounds, is caused by the vibration of respiratory structures, especially the soft palate. This vibration results in sound due to obstructed air movement during breathing while sleeping. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Mild myopia (HP:0025573): A mild form of myopia with up to -3.00 diopters. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
- Cerebral visual impairment (HP:0100704): A form of loss of vision caused by damage to the visual cortex rather than a defect in the eye. Evidence: TAS. Frequency: Occasional (HP:0040283). (ORPHA:412069)
These phenotypes are associated with the disease AHDC1-related intellectual disability-obstructive sleep apnea-mild dysmorphism syndrome (ORPHA:412069).