Deletion and duplication syndromes

Each cell in the human (except reproductive cells) body contains 46 chromosomes (we get 23 from our mother and 23 from father). Having too much or too few chromosomes means that our body has too many or too few genes or 'genetic instructions'. This results in abnormalities such as trisomies (Down, Edwards, and Patau syndrome) or abnormalities in the sex chromosomes (including Klinefelter, Turner, Jacobs, and Triple X syndrome). However, the number of chromosomes may be typical, but there might be missing or duplicated fraction of the chromosome. This is called deletion or duplication. Because such changes are tiny, they are often difficult to detect before birth. The NIFTY test technology, however, scans all chromosomes and can detect 60 deletion and duplication syndromes.

In this article

Deletion

A chromosomal deletion occurs when a fragment of the chromosome is lost. It can happen on any chromosome and can be of different size. The result of chromosomal deletion is the loss of genetic material, which normally provides instructions for the body. The consequences of the deletion depend on the size of the lost part and its location on the chromosome: in other words, what information did this missing fragment of genetic matter contain.

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Duplication

Chromosomal duplication is the opposite of deletion: it is the doubling of a part of the chromosome. As a result, the body has too much genetic material or (instructions.). The consequences of a duplication also depend on the size and location of the duplicated part of the chromosome.

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Clinical characteristics of deletions and duplications may include developmental retardation and intellectual developmental disorders, slowed growth, behavioural disorders, feeding problems, low muscle tone, seizures, characteristic facial features, and other abnormalities. Clinical characteristics vary significantly between deletions and duplications, so if chromosomal abnormalities are detected, we recommend consulting an expert who will be able to answer your questions.

Alpha Thalassemia, mental retardation syndrome

Causes severe mental and physical disability with facial anomalies. The characteristic facial features include wide-set eyes, epicanthic fold (upper eyelid covering the inner corner of the eye), a small triangle-shaped nose, flat face, and microcephaly. The majority of patients also have genital anomalies and a severe form of anaemia.

Androgen insensitivity syndrome (AIS)

Androgen insensitivity syndrome is a condition that affects sexual development before birth and during puberty. People with this condition are genetically male, with one X chromosome and one Y chromosome in each cell. Because their bodies are unable to respond to certain male sex hormones (called androgens), they may have mostly female external sex characteristics or signs of both male and female sexual development.

Angelman syndrome/Prader-Willi syndrome

Angelman syndrome affects the nervous system. Characteristic features include delayed development, intellectual disability, movement disorder and balance problems, specific behaviour (abnormal amount of constant joy) and severe speech impairment. Other clinical signs include distinctive facial features, pigmentary skin changes, seizures, and sleep problems.

Bannayan-Riley-Ruvalcaba syndrome (BRRS)

Bannayan-Riley-Ruvalcaba syndrome is a genetic condition characterised by a large head (macrocephaly), multiple noncancerous tumours and tumour-like growths called hamartomas, and dark freckles on the penis in males. The signs and symptoms of this syndrome are present from birth or become apparent in early childhood.

Branchiootorenal dysplasia syndrome (BOR)/Melnick-Fraser syndrome

Branchiootorenal (BOR) syndrome is a condition that disrupts the development of tissues in the neck and causes the malformation of ears and kidneys.

Cat eye syndrome (CES)

Cat eye syndrome (CES) is a rare chromosomal disorder with a highly variable clinical presentation. Most patients have multiple malformations affecting the eyes (iris coloboma), ears (preauricular pits and/or tags), anal region (anal atresia), heart, and kidneys. Intellectual disability is usually mild or borderline normal.

Chromosome 10q deletion syndrome

This deletion is accompanied by facial asymmetry, pronounced nose, narrow upper lip, low birth weight, short stature, fifth finger clinodactyly and male cryptorchidism (absence of one or both testes). People with deletion 10q have different forms of learning difficulties and delayed development.

Chromosome 10q22.3–q23.31 microdeletion syndrome

Recurrent deletions of chromosome 10q22.3–q23.31 have been associated with dysmorphic facial features, developmental delay, and multiple congenital anomalies.

Chromosome 18p deletion syndrome

The main clinical features of this deletion are mental disabilities, growth disturbances, head and face anomalies (round face, enlarged oral cavity), abnormal ears and anomalies of the limbs, sexual organs, brains, eyes, heart, and teeth.

Chromosome 18q deletion syndrome

The characteristics of this deletion are highly variable and include mental disorders, short stature, low muscular tone, hearing disorders, feet deformities, pointed toes, and enlarged mouth.

Cornelia de Lange syndrome (CDLS)

Cornelia de Lange syndrome is characterised by facial dysmorphism, elevated eyebrows, a unibrow (synophrys), curled nose, narrow lips, enlarged middle part of the upper lip, reduced lower jaw growth. Clinical features include developmental delays, growth and cognitive impairment, and limb malformations.

Cowden syndrome (CD)

Cowden syndrome characteristics include benign lesions in the common tissue (skin, mucous membrane, chest and thyroid), on the face (near and in the mouth) and on the limbs.

Cri du Chat (5p deletion) syndrome

Cri du Chat syndrome is characterised by intellectual disability, delayed development, microcephaly, low birth weight, and wider spacing between the eyes. Infants with this condition often have a high-pitched cry.

Dandy-Walker syndrome (DWS)

Dandy-Walker syndrome affects brain development, the primary development of the cerebellum (the part that coordinates movement). The syndrome's main feature is the enlarged fourth ventricle. Up to half of the affected individuals have intellectual disability, delay in the development of motor skills, muscle stiffness, and seizures.

DiGeorge syndrome type 2 (DGS2)

DiGeorge syndrome type 2 is characterised by several clinical problems such as cardiac congestion, decreased parathyroid function, deformed facial features, slow development, learning difficulties, and T-cell immunodeficiency.

Distal arthrogryposis type 2B (DA2B)

Common clinical features of type 2B distal arthrogryposis include clenched fist, overlapping fingers, camptodactyly, ulnar deviation, and positional foot deformities from birth. Patients with this syndrome are recognised by nasolabial folds, down slanting palpebral fissures, and small mouth.

Duchenne and Becker muscular dystrophy (DMD/BMD)

Muscular dystrophies are a group of genetic conditions characterised by progressive muscle weakness and wasting (atrophy). The Duchenne and Becker types of muscular dystrophy are two related conditions that primarily affect skeletal muscles, which are used for movement, and heart (cardiac) muscle. These forms of muscular dystrophy occur almost exclusively in males.

Dyggve-Melchior-Clausen syndrome (DMC)

DMC syndrome is a rare, progressive genetic condition characterised by abnormal skeletal development, microcephaly, and intellectual disability. Only about 100 cases have been reported to date.

Feingold syndrome

Feingold syndrome is an autosomal dominant disorder characterised by variable combinations of microcephaly, limb malformations, oesophageal and duodenal atresia, and learning disability/intellectual disability.

Holoprosencephaly type 1 (HPE1)

Holoprosencephaly (HPE1) is the most common structural malformation of the human forebrain and occurs after failed or abbreviated midline cleavage of the developing brain during the third and fourth week of gestation.

Holoprosencephaly type 4 (HPE4)

Holoprosencephaly type 4 is characterised by severe facial and brain anomalies. The degree of disability depends on the degree of brain injury. Severe forms of the syndrome are often fatal.

Holoprosencephaly type 6 (HPE6)

Type 6 holoprosencephaly is characterised by deformation of the brain and face.

Jacobsen syndrome

Jacobsen syndrome is a condition caused by a loss of genetic material from chromosome 11. The signs and symptoms of Jacobsen syndrome vary considerably. Most affected individuals have delayed development, cognitive impairment and learning difficulties, compulsive behaviour, short attention span and easy distractibility, autism, and distinctive facial features.

Langer-Giedion syndrome (LGS)

People with Langer-Giedion syndrome are mentally disabled and have facial anomalies involving large, protruding ears, round tip of the nose, enlarged upper lip, and sparse scalp hair. Other clinical features include anomalies of the shoulder blades, multiple exostosis (abnormal formations on the bone), and excess skin. Patients may also have blood in the uterus and fluid retention in the vaginal opening.

Leukodystrophy with 11q14.2–q14.3

Microdeletion 11q14.2–q14.3 can cause leukodystrophy, which is accompanied by epileptic seizures in infants, severe psychomotor disabilities, growth and developmental disorders, microcephaly, microphallus, structural brain disorders and facial anomalies (e.g., round nasal tip, forehead and eyelid deformities). Patients with leukodystrophy die during childhood.

Mental retardation, X-linked growth hormone deficiency (MRGH)

Mental retardation, X-linked, with isolated growth hormone deficiency: a disorder characterised by the association of variable degrees of intellectual disability with panhypopituitarism, variable combinations of hypothyroidism, delayed pubertal development, and short stature due to growth hormone deficiency.

Microphthalmia, syndromic 6, pituitary hypoplasia

Patients with this syndrome are characterised by the absence of one or both eyes, a brachycephaly (shorter skull), retrognathia (lower jaw deformity), small ears, anomalies of the fingers, an underdevelopment of the external genitalia, and a hypoplastic kidney. Patients have brain disorders such as a small cerebellum and the absence of specific brain structures.

Microphthalmia with linear skin defects

Microphthalmia with linear skin defects syndrome is a disorder that mainly affects females. In people with this condition, one or both eyes may be very small or poorly developed (microphthalmia). Affected individuals also typically have unusual linear skin markings on the head and neck.

Monosomy 9p syndrome

Monosomy 9p is a rare chromosomal anomaly characterised by psychomotor developmental delay, facial dysmorphism, single umbilical artery, omphalocele, inguinal or umbilical hernia, genital abnormalities, muscular hypotonia, and scoliosis.

Orofaciodigital syndrome

Orofaciodigital syndrome is a group of related conditions that affect the development of the oral cavity (the mouth and teeth), facial features, and digits (fingers and toes).

Panhypopituitarism, X-linked

This syndrome causes a reduced excretion of one or more hormones produced by the pituitary gland, which can lead to dwarfism in children and premature aging in adults. Disorders of gonadotropin secretion affect reproductive functions.

Potocki-Lupski syndrome (17p11.2 duplication syndrome)

It causes a mild form of intellectual disability including reduced cognitive abilities, behavioural disorders, attention deficit, hyperactivity, and sometimes autism. Most people with the syndrome have shorter stature.

Prader-Willi-like syndrome (SIM1 syndrome)

Prader-Willi-like syndrome is characterised by diminished foetal activity, obesity, muscular hypotonia, intellectual disability, short stature, hypogonadotropic hypogonadism, and small hands and feet.

Rieger syndrome type 1 (RIEG1)

Rieger syndrome is an autosomal dominant disorder of morphogenesis that results in abnormal development of the anterior segment of the eye, and results in blindness from glaucoma in approximately 50% of affected individuals. The syndrome is associate with systemic anomalies including dental hypoplasia, failure of involution of periumbilical skin, and maxillary hypoplasia.

Saethre-Chotzen syndrome (SCS)

Saethre-Chotzing syndrome is characterised by the presence of low-set frontal hairline, an irregular eyelid (ptosis), abnormal ear length, an enlarged parietal foramina (an opening in the cranial skull), a skin formation between fingers, an enlarged thumb, deformation of the fingers, and increased pressure in the brain.

Sensorineural deafness and male infertility

Sensorineural deafness and male infertility is a condition characterised by hearing loss and infertility.

Smith-Magenis syndrome

Smith-Magenis syndrome is a developmental disorder that affects many parts of the body. Major features of this condition include mild to moderate intellectual disability, delayed speech and language skills, distinctive facial features, sleep disturbances, and behavioural problems.

Split-hand/foot malformation type 3 – Ectrodactyly type 3 (SHFM3)

Ectrodactyly type 3 causes disorders such as fusion of a large number of toes and fingers, split palms and feet, and the absence and/or incomplete development of different bones of the hand, foot, fingers, and toes. Certain patients develop brain development deficiencies, mental disorders, and orofacial clefting.

Split-hand/foot malformation type 5 – Ectrodactyly type 5 (SHFM5)

Split-hand/split-foot malformation (SHFM) is a structural limb malformation which includes deformation of palms and feet, finger jointing, aplasia and/or hypoplasia of the phalanges, metacarpals, and metatarsals. Certain patients develop brain development deficiencies, mental disorders, and orofacial clefting.

Syndrome diaphragmatic hernia, congenital (HCD/DIH)

Congenital diaphragmatic hernia (CDH) refers to a group of congenital defects in the structural integrity of the diaphragm, which is often associated with lethal pulmonary hypoplasia and pulmonary hypertension. Prevalence in newborns ranges from 1 in 2,500 to 1 in 4,000, and there is a 30% to 60% mortality rate.

Trichorhinophalangeal syndrome type I (TRPS1)

Trichorhinophalangeal syndrome type I (TRPS1) is a condition that causes bone and joint malformations, distinctive facial features, and abnormalities of the skin, hair, teeth, sweat glands, and nails. The name of the condition describes some of the areas of the body that are commonly affected: hair (tricho-), nose (rhino-), and fingers and toes (phalangeal).

Van der Woude syndrome (VWS)

Van der Woude syndrome (VWS) is a rare congenital genetic dysmorphic syndrome characterised by paramedian lower-lip fistulae, cleft lip with or without cleft palate, or isolated cleft palate.

WAGR syndrome and aniridia II

Most people with WAGR syndrome have aniridia, underdevelopment or absence of the iris, which can reduce the sharpness of vision and increase sensitivity to light. Other signs of WAGR syndrome are intellectual disability, genitourinary anomalies, and kidney problems.

Wilms tumour 1 (WT1)

Wilms tumour 1 is one of the most common tumours that occur in childhood (1 per 10,000 children) and represents 8% of all cancers in children. It is believed to result from the malignant transformation of abnormally persistent renal stem cells that retain embryonic differentiation potential.

X-linked lymphoproliferative syndrome (XLP)

X-linked lymphoproliferative (XLP) syndrome is an extremely rare inherited immunodeficiency disorder characterised by a defective immune system easily infected with the Epstein-Barr virus, which is the cause of infectious mononucleosis.

Xp11.22–p11.23 microduplication syndrome

Clinical signs of this microdeletion are independent of gender and duplication size. Typical clinical signs are various forms of seizures. Affected individuals are shy and stubborn, and their behaviour is similar to that of a person with autism.

1p36 microdeletion syndrome

1p36 deletion syndrome is a disorder that typically causes severe intellectual disability. Most affected individuals do not speak or speak only a few words. They may have temper tantrums, bite themselves, or exhibit other behavioural problems. Most have structural abnormalities of the brain, and seizures occur in more than half of the individuals with this disorder. Affected individuals usually have weak muscle tone (hypotonia) and swallowing difficulties (dysphagia).

1q41–q42 microdeletion syndrome

The common clinical features of microdeletion 1q41–q42 include a significant developmental delay and distinct facial dysmorphisms such as deep-seated eyes, broad nasal tip and depressed nasal bridge. In some cases, microcephaly, cleft palate, clubfeet, seizures, and short stature are present.

2q33.1 deletion syndrome ("Glass syndrome")

Glass syndrome is characterised by an intellectual disability of variable severity and dysmorphic facial features, including micrognathia, downward slanting palpebral fissures, cleft palate, and crowded teeth.

5q21.1–q31.2 deletion syndrome

The syndrome is primarily recognised based on a significantly modified face, which includes lower forehead, raised eyebrows, a unibrow (synophrys), tight nose, reduced growth of the lower jaw (maxillary prognathism), the enlarged middle part of the upper lip, and narrow lips. The main clinical features are prefrontal and postnatal developmental delay, mental disabilities and abnormal growth of the upper limbs.

8p23.1 deletion syndrome

The clinical features of deletion 8p23.1 are congenital heart disease, congenital diaphragmatic hernia, developmental delay, and typical behavioural disorders – hyperactivity and impulsiveness.

8p23.1 duplication syndrome

8p23.1 duplication syndrome is a rare chromosomal anomaly, resulting from the partial duplication of the short arm of chromosome 8, with a highly variable phenotype, principally characterised by mild to moderate developmental delay, intellectual disability, mild facial dysmorphism, and congenital cardiac anomalies.

11q11–q13.3 duplication syndrome

The syndrome is characterised by congenital deafness due to an underdeveloped inner ear. The duplication may also cause underdevelopment of the external part of the ears. Very small teeth are also a common feature.

12q14 microdeletion syndrome

Microdeletion 12q14 leads to a mild form of mental disability, early developmental disorders, and osteopoikilosis (excessive bone density leading to pain). Patients are characterised by short stature.

14q11–q22 deletion syndrome

Common features of patients with 14q11–q22 deletion syndrome are microcephaly, hypotonia, poor growth, intellectual disability with poor eye contact, hypoplasia of the corpus callosum and dysmorphic features, including short nose, long philtrum, and flat nasal bridge.

15q26 overgrowth syndrome

Overgrowth syndrome is characterised by renal anomalies (45%), including horseshoe kidney and renal agenesis (one or both foetal kidneys fail to develop). Hydronephrosis (inadequate functioning of the kidneys), vesicoureteral reflux (backward flow of urine), polycystic kidney and right renal pelvic duplication are common as well. People with this syndrome can also be mentally challenged, have developmental delay, and tall stature.

16p11.2–p12.2 microdeletion syndrome

It is accompanied by facial anomalies, including a flattened face, down-slanting palpebral fissures, and eye anomaly. Small ears and mental disability are also typical for this microdeletion.

16p11.2–p12.2 microduplication syndrome

The 16p11.2–p12.2 duplication syndrome is a recurrent genomic disorder with a variable phenotype including developmental delay, dysmorphic features, mild to severe intellectual disability, autism, obsessive or stereotyped behaviour, short stature, and anomalies of the hands and fingers.

17q21.31 deletion syndrome

17q21.31 deletion syndrome or Koolen-de Vries syndrome is a disorder characterised by developmental delay and mild to moderate intellectual disability. People with this disorder are typically described as cheerful, sociable, and cooperative. They usually have weak muscle tone (hypotonia) in childhood. About half have recurrent seizures (epilepsy). Affected individuals often have distinctive facial features, cardiac abnormalities, kidney problems, and skeletal anomalies.

17q21.31 duplication syndrome

The duplication syndrome 17q21.31 refers to short stature, microcephaly, finger anomalies, hirsutism (excessive body hair), atopic dermatitis, digestive problems, facial anomalies (small mouth, anomalies of the ears, small nose) and anomalies of the toes. People with this duplication are mentally challenged, have difficulties in social integration, poor motor skills and behavioural problems (aggression, hyperactivity, obsessive disorders, communication disorders).

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