Schinzel syndrome, also known as ulnar-mammary syndrome, is a rare inherited disorder characterized by abnormalities of the bones of the hands and forearms in association with underdevelopment (hypoplasia) and dysfunction of certain sweat (apocrine) glands and/or the breasts (mammary glands). Abnormalities affecting the hands and/or forearms range from underdevelopment of the bone in the tip of the fifth finger (hypoplastic terminal phalanx) to underdevelopment or complete absence of the bone on the outer aspect of the forearm (ulna).
In addition, certain sweat glands such as those located under the arms may be underdeveloped or absent, resulting in diminished ability or inability to sweat (perspire). In some cases, the breasts (mammary glands) may also be underdeveloped or absent; as a result, affected females exhibit a diminished ability or an inability to produce milk (lactate).
The range and severity of physical abnormalities associated with Schinzel syndrome varies greatly among affected individuals; some cases may be very mild, while others may be more severe.
Schinzel syndrome, also known as ulnar-mammary syndrome (UMS), is an extremely rare inherited disorder characterized by abnormalities affecting the bones of the hands and forearms and/or underdevelopment (hypoplasia) and dysfunction of certain sweat glands (apocrine) and/or the breasts (mammary glands). The physical features and symptoms associated with Schinzel syndrome vary greatly from case to case.
Abnormalities affecting the hands and/or forearms may range from underdevelopment (hypoplasia) of the bone in the tip of the fifth finger (hypoplastic terminal phalanx) to underdevelopment or complete absence of the bone on the outer aspect of the forearm (ulna); underdevelopment (hypoplasia), abnormal bending (bowing), or absence of the forearm bone on the thumb side of the arm (radius); and/or hypoplasia or absence of certain fingers, such as the third, fourth, and/or fifth fingers (oligodactyly). In some cases, certain bones of the fingers (e.g., phalanges of the fourth and fifth digits), within the body of the hand (metacarpals), and/or within the wrist (carpal bones) may be underdeveloped or absent. In addition, in some infants with digital hypoplasia, certain fingers may be permanently fixed in a flexed position (camptodactyly) and/or the fifth fingers may be abnormally bent (clinodactyly). Affected infants may have additional finger (digital) abnormalities with or without ulnar, radial, and/or digital malformations on the other side of the body (contralateral limb deficiencies), such as extra digits on the “pinky” side of the hand (postaxial polydactyly). In rare cases, infants with Schinzel syndrome may also exhibit underdevelopment of the long bone of the upper arm (humerus). In affected individuals, digital and/or upper limb abnormalities tend to vary in severity from side to side (asymmetry). Malformations affecting the fingers, hands, and arms may lead to complications, such as limitations in range of movement. In rare cases, individuals with the disorder may also exhibit underdeveloped, abnormally short, or absent toes.
In some cases, individuals with Schinzel syndrome may also have abnormalities of certain sweat glands such as those under the arms (axillary apocrine glands). Such abnormalities may include underdevelopment (hypoplasia) or absence of the sweat glands, resulting in a reduced ability or complete inability to sweat (perspire). Affected individuals may also have little or no hair under the arms and lack body odor. In addition, in some cases, affected individuals may exhibit underdevelopment or complete absence of the nipples and/or breasts (mammary glands) and, in affected females, the breasts may be unable to produce milk (lactate). However, in other cases, affected individuals may have normal breast development with, in affected females, the ability to produce milk.
In some cases, affected individuals may experience delayed growth that, in some cases, may result in short stature. However, in other cases, affected individuals may experience late “catch-up” growth.
In addition, individuals with Schinzel syndrome may also have genital abnormalities. In some cases, affected males may have abnormally low levels of testicular function (hypogenitalism), resulting in delayed development of secondary sexual characteristics (puberty) (e.g., deepening of the voice, characteristic hair growth patterns, sudden increase in growth and development of the testes and scrotum, etc.). In addition, affected males may have an abnormally small penis and one or both of the testes may fail to descend into the scrotum (cryptorchidism). In affected females, the thin membrane that normally partially covers the vaginal opening (hymen) may completely cover the vaginal opening (imperforate hymen), potentially causing menstrual blood to collect in the vagina. In addition, in some cases, the uterus may be abnormally shaped (bicornate uterus).
In some cases, individuals with Schinzel syndrome may have additional abnormalities such as excessive body mass (obesity), absence or improper positioning of certain teeth (ectopic upper canines), and/or malformations of bones of the spine (vertebrae) such as abnormal side-to-side curvature of the spine (scoliosis). In addition, the soft-tissue structure that hangs at the back of the throat (uvula) may be abnormally divided (bifid). In some cases, the voice box (larynx) may be covered with an abnormal fibrous membrane (congenital laryngeal web) that involves the vocal cords, the two fibrous bands of tissue that are essential for voice production. In such cases, affected individuals may experience some difficulties with swallowing, breathing (aspiration), and/or speech. In addition, some affected infants may exhibit abnormal narrowing (stenosis) of the band of muscle fibers (pyloric sphincter) at the junction between the stomach and the small intestine (pyloric stenosis), potentially resulting in obstruction of the normal flow of stomach contents into the small intestine. In a few cases, affected individuals may have protrusion of portions of the large intestine through an abnormal opening in layers of muscle lining the abdominal cavity (inguinal hernia). In addition, the anus may be abnormally narrowed or closed off (anal stenosis or atresia).
In addition, according to the medical literature, three of four affected individuals within one family (kindred) had a ventricular septal defect (VSD), a heart abnormality that is present at birth (congenital). In individuals with VSDs, there is an abnormal opening in the fibrous partition (septum) that separates the two lower chambers (ventricles) of the heart. The size and location of the defect determine the range and severity of the symptoms. Because it is not clear whether this is an incidental finding, its implications are not fully understood. (For more information on this disorder, choose “Ventricular Septal Defect” as your search term in the Rare Disease Database.)
Schinzel syndrome is inherited as an autosomal dominant genetic trait. It occurs as a result of an abnormality in a gene on the long arm of chromosome 12 (12q24.1).
Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Human body cells normally have 46 chromosomes. Pairs of human chromosomes are numbered from 1 through 22 and the sex chromosomes are designated X and Y. Males have one X and one Y chromosome and females have two X chromosomes. Each chromosome has a short arm designated “p” and a long arm designated “q”. Chromosomes are further sub-divided into many bands that are numbered. For example, “chromosome 12q24.1” refers to band 24.1 on the long arm of chromosome 12. The numbered bands specify the location of the thousands of genes that are present on each chromosome.
Genetic diseases are determined by the combination of genes for a particular trait that are on the chromosomes received from the father and the mother.
All individuals carry a few abnormal genes. Parents who are close relatives (consanguineous) have a higher chance than unrelated parents to both carry the same abnormal gene, which increases the risk to have children with a recessive genetic disorder.
Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary for the appearance of the disease. The abnormal gene can be inherited from either parent, or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy regardless of the sex of the resulting child.
The gene responsible for Schinzel syndrome is called “TBX3.” The gene (which is a member of the “T-box” transcription factor family) plays a role in the development of the outer aspect of the upper limbs (ulnar or postaxial limb anomalies) during embryonic growth.
Schinzel syndrome is a very rare disorder that affects males and females in equal numbers. Between 50 and 75 cases have been reported in the medical literature. Of these, about 33 cases involve individuals within one family (kindred) from Utah. The syndrome has been described in Asians, Africans, and Europeans.
Individuals with this syndrome who have few symptoms may never be diagnosed with the disorder; therefore, it may be difficult to determine the true frequency of the syndrome in the general population.
The syndrome was first identified by A. Schinzel in 1973. At that time, it was labeled Schinzel syndrome. All of Schinzel’s reported cases involved males. P.D. Pallister identified a strikingly similar syndrome in 1976, which became known as Pallister syndrome or ulnar-mammary syndrome of Pallister, in which most cases involved females. Today, although some researchers consider these two distinct disorders, most consider them the same disease entity.
In some cases, a diagnosis of Schinzel syndrome may be made at birth based upon a thorough clinical evaluation, the identification of characteristic physical findings, and specialized imaging techniques. Such imaging studies may be conducted to confirm and/or characterize bone abnormalities affecting the fingers, hands, wrists, and/or arms; certain genital abnormalities (e.g., bicornate uterus in females, cryptorchidism in males); and/or other malformations (e.g., pyloric stenosis, inguinal hernia). Specialized tests may also be conducted to detect and verify dysfunction of certain sweat (apocrine) glands and/or the mammary glands in affected females. In addition, in some cases, additional testing may be conducted (e.g., echocardiograms, electrocardiograms, cardiac catheterization, specialized x-ray studies, etc.) to detect the presence of and/or characterize ventricular septal defects, which have been reported in one family with the disorder.
The treatment of Schinzel syndrome is directed toward the specific symptoms that are apparent in each individual. Treatment may require the coordinated efforts of a team of specialists. Pediatricians; physicians who specialize in diagnosing and treating disorders of the skeleton (orthopedists), the urogenital tract in males (urologists), the genital tract in females (gynecologists), and/or the endocrine glands (endocrinologists); dental specialists; physical therapists; and/or other health care professionals may need to systematically and comprehensively plan an affected child's treatment.
Depending upon the severity of any limb and digital abnormalities, children with ulnar-mammary syndrome may experience difficulty performing certain tasks that require coordination of voluntary movements (motor skills). Treatment may consist of corrective or reconstructive surgery; the use of artificial replacements for portions of the forearms and hands that may be underdeveloped or absent (limb prosthetics); and/or physical therapy to help individuals enhance their motor skills.
In some cases, reconstructive surgery may also be beneficial for affected individuals with nipple and breast abnormalities. In addition, in some affected females, surgery may be recommended to open (perforate) the hymen (hymenotomy). In affected males, surgery may be performed to move undescended testes into the scrotum (orchiopexy) and attach them in a fixed position to prevent retraction. In some cases, surgery may also be performed to correct pyloric stenosis (pyloromyotomy), inguinal hernias, and/or anal stenosis or atresia.
Individuals with this syndrome may also benefit from special social support and vocational and occupational services. Genetic counseling will be of benefit for affected individuals and their families. Other treatment is symptomatic and supportive.
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