NORD gratefully acknowledges Christa Lese Martin, PhD and Eli Williams, PhD, Department of Human Genetics, Emory University, for assistance in the preparation of this report.
Chromosome 10, monosomy 10p is a rare chromosomal disorder in which the end (distal) portion of the short arm (p) of chromosome 10 is missing (deleted or monosomic). The range and severity of symptoms and findings may be variable, depending upon the exact size or location of the deletion on chromosome 10p. However, associated features often include severe intellectual disability; growth delays after birth (postnatal growth retardation); distinctive malformations of the skull and facial (craniofacial) region; a short neck; and/or structural defects of the heart that are present at birth (congenital heart defects). Several cases have also been reported in which affected individuals have some features of DiGeorge syndrome (DGS). DGS is a congenital disorder characterized by underdevelopment or absence of the thymus and parathyroid glands, potentially causing abnormalities of the immune system, deficient production of parathyroid hormone (hypoparathyroidism), a heart defect, and associated findings. In many cases, chromosome 10, monosomy 10p appears to occur spontaneously (de novo) for unknown reasons.
The symptoms and physical findings associated with chromosome 10, monosomy 10p may vary in range and severity from case to case. However, according to reports in the medical literature, most individuals with the disorder are affected by severe intellectual disability and delays in the acquisition of skills requiring the coordination of mental and motor activities (psychomotor retardation). Monosomy 10p is also frequently associated with growth delays after birth, resulting in short stature.
Affected infants and children also typically have certain distinctive abnormalities of the skull and facial (craniofacial) region. Such malformations may include an abnormally small head (microcephaly) with a protruding forehead (frontal bossing); a small jaw (micrognathia); a low nasal bridge and upturned (anteverted) nostrils; malformed, low set ears; and a short neck. Additional craniofacial defects may also be present, such as widely spaced eyes (ocular hypertelorism); short, downwardly slanting eyelid folds (palpebral fissures); vertical skin folds covering the eyes’ inner corners (epicanthal folds); drooping of the upper eyelids (ptosis); and abnormal deviation of one eye in relation to the other (strabismus). Less commonly, the disorder may be associated with incomplete closure of the roof of the mouth (cleft palate) and an abnormal groove in the upper lip (cleft lip).
Individuals with monosomy 10p may also have widely spaced nipples; foot malformations; and/or structural defects of the heart (congenital heart defects). In addition, the disorder may be associated with abnormalities of the urinary tract and the genitals, such as undescended testes (cryptorchidism) and an underdeveloped (hypoplastic) scrotum in affected males. Some individuals may also have dysfunction of the lowest region of the brain known as the brainstem, which helps to convey messages traveling between other brain regions and the spinal cord and has sensory, motor, and reflex functions. In individuals with monosomy 10p, brainstem dysfunction may be associated with severe hearing loss due to impaired conversion of sound vibrations and failed transmission of nerve impulses from the inner ear via the auditory nerve to the brain (i.e., sensorineural hearing loss).
As mentioned previously, monosomy 10p may often be associated with features of DiGeorge syndrome (DGS). DGS is a congenital disorder resulting from improper development of embryonic structures that form the thymus and parathyroid glands. Other embryonic structures that develop at about the same time may also sometimes be affected, potentially leading to certain defects of the heart and its major blood vessels (cardiovascular defects) and/or craniofacial malformations. The thymus is thought to play a crucial role in the body’s immune system beginning during fetal development until about puberty. It serves to promote the maturation of certain precursor* cells into T lymphocytes, which are specialized white blood cells that assist in the recognition or destruction of foreign proteins (antigens), such as certain invading microorganisms. (*A precursor is a biological forerunner or a substance that precedes and is the source of another, typically more mature or active substance.) The parathyroid glands are two pairs of relatively small glands that produce parathyroid hormone, which helps to regulate blood calcium levels.
Individuals with monosomy 10p who have features of DGS typically have variable degrees of hypoplasia or underdevelopment of the thymus and parathyroid glands. This is sometimes referred to as “partial DiGeorge syndrome.” Hypoplasia of the thymus may lead to deficient activity of the immune system and impaired resistance to certain viral, bacterial, or fungal infections. In other cases, however, some individuals with partial DiGeorge syndrome may not appear to have an increased susceptibility to recurrent infections.
In those with hypoplasia of the parathyroid glands, deficient secretion of parathyroid hormone (hypoparathyroidism) may lead to low calcium blood levels (hypocalcemia) and associated findings during the first days of life (neonatal tetany). Such features may include muscle cramping and spasms, convulsions, tremors, spasmodic closure of the larynx (laryngospasm), and/or other findings.
Cardiovascular abnormalities that have been reported in association with DGS include defects of the aorta or the major artery that supplies oxygenated blood to most of the body; an abnormal opening in the fibrous partition (septum) that separates the lower or upper chambers of the heart (ventricular or atrial septal defects); and/or other congenital defects.
Experts suggest that certain abnormalities frequently seen in individuals with monosomy 10p may be absent in those with classic DiGeorge syndrome (i.e., DGS that results from minute deletions of material from the long arm of chromosome 22). For example, severe intellectual disability and growth delays are seen in most individuals with monosomy 10p yet may not be apparent in those with classic DGS. Sensorineural deafness, a finding reported in a number of individuals with monosomy 10p, has not been associated with classic DGS. In addition, abnormalities of the heart and its major blood vessels are more frequent in classic DGS than monosomy 10p. (For further information, please see the “Causes” section of this report below.)
Chromosome 10, monosomy 10p is a rare chromosomal abnormality in which there is deletion (monosomy) of the end (distal) portion of the short arm (p) of chromosome 10. Chromosomes are found in the nucleus of all body cells. They carry the genetic characteristics of each individual. Pairs of human chromosomes are numbered from 1 through 22, with an unequal 23rd pair of X and Y chromosomes for males and two X chromosomes for females. Each chromosome has a short arm designated as “p” and a long arm identified by the letter “q”. Chromosomes are further subdivided into bands that are numbered.
In individuals with monosomy 10p, the range and severity of associated symptoms and findings may vary, depending upon the exact length or location of the deleted portion of chromosome 10p. Deletions occurring closer to the centromere result in in a phenotype with similar features to DiGeorge syndrome, as discussed. More distal deletions are associated with mutations in a specific gene, GATA3, resulting in hypoparathyroidism (see “symptoms” section), deafness, and renal (kidney) abnormalities, and refered to as HDR syndrome. The GATA3 gene encodes a protein involved in the embryonic development of these three tissues, i.e. parathyroid glands, auditory system, and kidneys. A recent study carried out molecular and clinical characterization of patients with overlapping 10p deletions. These studies showed that individuals with partial deletions 10p14-p15 may exhibit severe intellectual disability, language impairments and autistic behaviors.
In some cases, monosomy 10p appears to occur spontaneously (de novo) for unknown reasons very early in embryonic development. The parents of a child with a “de novo” deletion usually have normal chromosomes and a relatively low risk of having another child with the chromosomal abnormality. In other cases, monosomy 10p may result from a translocation involving chromosome 10p and another chromosome or chromosomes. Translocations occur when regions of certain chromosomes break off and are rearranged, resulting in shifting of genetic material and an altered set of chromosomes. Such translocations may occur spontaneously for unknown reasons (de novo) or be transmitted by a parent who is a carrier of a “balanced” translocation. (If a chromosomal rearrangement is balanced–i.e., consists of an altered but balanced set of chromosomes–it is usually harmless to the carrier. However, such a chromosomal rearrangement may be associated with an increased risk of abnormal chromosomal development in the carrier’s offspring. Chromosomal analysis may determine whether a parent has a balanced translocation.)
As mentioned above, monosomy 10p may often be associated with features of DiGeorge syndrome (DGS), a condition caused by abnormal development of embryonic structures that form the thymus and parathyroid glands and, in some instances, other embryonic structures. DGS most commonly results from spontaneous (sporadic), minute deletions (microdeletions) of material from the long arm (q) of chromosome 22 (22q11.2 [known as the “DiGeorge syndrome chromosomal region” or “DGCR”). Such cases are sometimes referred to as “classical DiGeorge syndrome.” However, phenotypes similar to those observed in DiGeorge syndrome can also have other underlying causes, such as various chromosomal abnormalities, including monosomy 10p and fetal exposure to alcohol or certain vitamin A-like compounds (retinoids) during pregnancy. (For further information on classic DiGeorge syndrome, please use “DiGeorge” as your search term in the Rare Disease Database. For more on chromosome 22, deletion 22q11.2, please see the “Related Disorders” section below.)
Chromosome 10, monosomy 10p is typically evident at birth (congenital). Since the disorder was originally reported in the medical literature in 1970, over 46 cases have been recorded. In such observed cases, males appear to be more frequently affected than females.
In some cases, a diagnosis of chromosome 10, monosomy 10p may be suggested before birth (prenatally) by tests such as amniocentesis or chorionic villus sampling (CVS). During amniocentesis, a sample of fluid that surrounds the developing fetus is removed and analyzed. CVS involves the removal of tissue samples from a portion of the placenta. Chromosomal analysis performed on the fluid or tissue samples may reveal the presence of monosomy 10p.
Chromosome 10, monosomy 10p may also be diagnosed or confirmed after birth based upon a thorough clinical evaluation, detection of characteristic physical findings, andcytogeneticanalysis, either by G-banded karyotype analysis or chromosomal microarray analysis. Specialized tests may also be conducted to help detect and/or characterize certain abnormalities that may be associated with the disorder. These may include tests to assess blood calcium levels; immunologic studies; advanced imaging techniques to confirm or characterize abnormalities of the thymus, parathyroid glands, and brain (e.g., ultrasonography, computed tomography [CT] scanning, magnetic resonance imaging [MRI]); and studies to evaluate the structure and function of the heart (e.g., x-ray imaging, electrocardiogram [EKG], echocardiogram, cardiac catheterization). Testing known as brainstem auditory evoked response (BAER) may also be conducted to screen affected infants for hearing impairment. During BAER, clicking sounds are used and responses are recorded to evaluate hearing (auditory) pathways of the brainstem. In some cases, additional diagnostic studies may also be recommended.
The treatment of Chromosome 10, monosomy 10p is directed toward the specific symptoms that are apparent in each individual. Such treatment may require the coordinated efforts of a team of medical professionals, such as pediatricians; surgeons; specialists in the functioning of the immune system (immunologists); endocrine disorder specialists (endocrinologists); physicians who diagnose and treat heart abnormalities (cardiologists); hearing specialists; and/or other health care professionals.
The treatment of affected individuals is symptomatic and supportive. For those with hypoparathyroidism, treatment may include administration of calcium and vitamin D, which aids in calcium absorption. For individuals with an increased susceptibility to recurrent infections, the use of particular antibiotic, antiviral, and antifungal medications and other agents may be required to help prevent and aggressively treat certain infections. (For further information on disease management for features of DiGeorge syndrome, please choose "DiGeorge" as your search term in the Rare Disease Database.)
Physicians may also recommend corrective surgery for certain craniofacial and/or other malformations potentially associated with monosomy 10p. In addition, for those with congenital heart defects, treatment with certain medications, surgical intervention, and/or other measures may be necessary. The specific surgical procedures performed will depend upon the severity and location of the anatomical abnormalities, their associated symptoms, and other factors.
Early intervention may be important in ensuring that affected children reach their potential. Special services that may be beneficial include special education, physical therapy, and/or other medical, social, and/or vocational services. Genetic counseling will also be of benefit for families of affected children. Other treatment for this disorder is symptomatic and supportive.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]ih.gov
For information about clinical trials sponsored by private sources, contact:
Contact for additional information about chromosome 10, monosomy 10p:
Christa Lese Martin, PhD, FACMG
Operations Director, Emory Genetics Laboratory
Department of Human Genetics
Emory University School of Medicine
615 Michael St., Suite 301
Atlanta, GA 30322
Tel: 404-727-3201; 404-778-8502
email: [email protected]
(Please note that some of these organizations may provide information concerning certain conditions potentially associated with this disorder [e.g., mental retardation, craniofacial abnormalities, hearing impairment, hypoparathyroidism, immune abnormalities, congenital heart defects, etc.].)
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FROM THE INTERNET
Online Mendelian Inheritance in Man (OMIM). The Johns Hopkins University. DiGeorge Syndrome; DGS. Entry No: 188400. Last Edited January 12, 2011. Available at: http://www.ncbi.nlm.nih.gov/omim/. Accessed March 15, 2011.
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