The specific symptoms of trisomy 9p can vary greatly from one person to another due, in part, to the specific length of the duplicated material on chromosome 9p.
Trisomy 9p is often characterized by low muscle tone (hypotonia) as well as growth deficiency and delayed bone maturation, which means that the rate of growth and development of the Bones is slower than in individuals with 46 chromosomes. Hypotonia can affect infants, most often related to Difficulty feeding, resulting in the failure to gain weight and grow at the expected rate (Failure to thrive). In general, growth deficiency primarily begins after birth (postnatally). Some infants may also experience oropharyngeal dysphagia, in which there is difficulty emptying food or drink from the back of the throat at the back of the mouth (oropharynx) into the esophagus. However, reports indicate that, in those with larger trisomic segments (e.g., through bands 9q22 or 9q32), growth deficiency may begin before birth (intrauterine growth retardation). Microcephaly, a condition indicates that the head circumference is smaller than would be expected based upon an infant’s age and gender, is also apparent in infancy.
In many cases, trisomy 9p is also associated with varying degrees of intellectual disability, ranging from moderate to severe, and delays in the acquisition of skills requiring the coordination of mental and physical activities (developmental coordination disorder). According to reports in the medical literature, language development appears to be most severely delayed. Learning disabilities, ranging from mild to severe, also occur. Intellectual and learning issues go hand in hand. Intellectual and learning disabilities represent a broad range, especially when the children with partial trisomy 9p are considered as well. The gap with typically developing peers will often widen with age.
Many infants and children with trisomy 9p also have a characteristic facial appearance. Most individuals with this condition present with a short and broad head (brachycephaly); a wide mouth with downturned corners; a prominent, relatively bulbous nose; large, low-set, “cup-shaped” ears; and/or a short vertical groove in the center of the upper lip (philtrum). Characteristic eye abnormalities may also be present, such as deeply set, widely spaced eyes; downwardly slanting eyelid folds (palpebral fissures); vertical skin folds that may cover the eyes’ inner corners (epicanthal folds); and/or abnormal deviation of one eye in relation to the other (strabismus). Some affected infants may also have a short, webbed neck; a highly arched roof of the mouth (palate); and/or widely spaced nipples. Teeth may erupt later than expected and may emerge crooked. In addition, in those with larger trisomic segments, additional craniofacial features may include a small jaw (micrognathia), incomplete closure (clefting) of the roof of the mouth (cleft palate), and/or an abnormal groove or gap in the upper lip (cleft lip).
Many individuals with trisomy 9p may also have various anomalies of the hands and feet. These may include decreased length of specific Bones of the fingers and toes (phalanges) and within the hands (metacarpals) and feet (metatarsals); short fingers and toes (digits) with small nails; and/or the pinkies may be fixed or ‘locked’ in a bent position (clinodactyly). The syndrome may also be associated with unusual, distinctive skin ridge patterns of the fingers and hands (abnormal dermatoglyphics), including a single flexion crease on the fifth fingers and a reduced total finger ridge count. Less often, a single crease across the palms may also be present.
In some cases, trisomy 9p may be associated with skeletal defects including delayed closure of the “soft spots” (fontanels) and the fibrous joints (cranial sutures) between certain? Bones of the skull; a deformity in which the foot is twisted out of shape or position (clubfoot); and/or abnormal front-to-back or side-to-side curvature of the spine (kyphoscoliosis) that may develop during the second decade of life. Less commonly, partial webbing (syndactyly) of certain fingers and toes and dislocation of the hips at birth have been noted.
Approximately five to 25% of children with may also have congenital heart defects, particularly an abnormal opening in the partition (septum) that separates the two lower chambers (ventricles) of the heart (ventricular septal defects [VSDs]). In those with cardiac defects, associated symptoms and findings may vary, depending upon the size, nature, and/or combination of heart malformations present. For example, in some cases, such as those with small, isolated VSDs, no symptoms may be apparent (asymptomatic). However, in other instances, such as children with larger VSDs and/or other cardiac defects, associated symptoms and findings may include difficulties feeding, Shortness of breath, profuse Sweating, Irritability, Fatigue, bluish discoloration of the skin and/or mucous membranes (cyanosis. In severe cases, congenital heart disease may lead to potentially life-threatening complications. Surgery may be necessary to remedy heart defects along with follow-up care and monitoring.
In some instances, additional physical abnormalities have been reported. These have included genital malformations in affected males, such as undescended testes (cryptorchidism) and/or abnormal placement of the urinary opening (hypospadias); kidney (renal) malformations; protrusion of part of the intestine and the fold of fatty membrane in front of the intestine (omentum) through a defect in the abdominal wall at the navel (umbilical hernia); and/or hydrocephalus, in which blockage of the normal flow of spinal fluid leads to excessive amounts of cerebrospinal (CSF) fluid accumulating in and around the brain. This leads to abnormally high pressure within the skull and Swelling of the head, and can result in neurological impairment. CSF is the watery protective fluid that circulates through the cavities (ventricles) of the brain, the canal containing the spinal cord (spinal canal), and the space between layers of the protective membranes (meninges) surrounding the brain and spinal cord (i.e., subarachnoid space). Depending upon the age at symptom onset and other factors, associated symptoms may include sudden episodes of uncontrolled electrical activity in the brain (Seizures), Irritability, Vomiting, Headache, loss of coordination, deteriorating mental functioning, and/or other findings.
Some individuals may also develop a brain malformation known as Dandy-Walker malformation (DWM). DWM occurs during embryonic development of the cerebellum and 4th ventricle. The cerebellum is an area at the back of the brain that helps coordinate movement, and, to a lesser extent, may be involved with some cognitive and behavioral functions. The 4th ventricle is a space around the cerebellum that channels fluid from inside to around the outside of the brain. DWM is characterized by improper development (e.g. small size and abnormal position) of the middle part of the cerebellum known as the cerebellar vermis, cystic enlargement of the 4th ventricle and enlargement of the base of the skull (posterior fossa). DWM may be associated with hydrocephalus.
Affected children may be below average height for their age (short stature). In some cases, affected children have been diagnosed with growth hormone deficiency.