TAR syndrome, Thrombocytopenia-Absent Radius Syndrome in English, is understood by medical science to be a malformation syndrome whose leading symptoms include nonunion of the spokes and thrombocytopenia. The cause of the syndrome is probably a hereditary gene mutation. Treatment consists primarily of platelet transfusion during the first few years of life.
What is TAR syndrome?
TAR syndrome is a complex of multiple malformations that manifests in the neonatal period. The leading symptoms of the hereditary malformation syndrome are bilateral nonunion of the radius and platelet deficiency. Because of the symptoms, the syndrome is sometimes referred to as radius aplasia-thrombocytopenia syndrome. TAR syndrome has been described in just over 100 cases to date. An exact prevalence is not known, but the symptom complex is considered relatively rare. The syndrome was first described in 1929 by the US-Americans H. M. Greenwald and J. Sherman. According to previous documentation, females are slightly more frequently affected by the malformations than the male sex. Because of its rarity, the syndrome has not been conclusively researched. Causal research has provided partial successes, but so far has not been able to provide a sufficient explanation for the overall complex.
Causes
In 2007, a possible cause of TAR syndrome was identified that corresponds to a genetic mutation. Thus, partial symptoms of the complex are caused by a microdeletion on chromosome 1 in gene locus q21.1. In this context, we are talking about the 1q21.1 deletion syndrome. Chromosome 1 has been associated with numerous hereditary diseases. For example, mutations at this gene locus can cause Usher syndrome, Gaucher’s disease or Alzheimer’s disease. Chromosome 1 is present in all body cells as a chromosome pair and corresponds to the largest human chromosome. The mutation associated with TAR syndrome appears to be necessarily present in all patients. However, the mutation does not adequately explain the individual symptoms of the syndrome. TAR syndrome is considered to be a hereditary disease. Familial clustering has been observed in the cases documented to date. Inheritance appears to be in the autosomal recessive mode of inheritance and to occur with a relatively large variability in manifestation.
Symptoms, complaints, and signs
All patients with TAR syndrome suffer from thrombocytopenia. The lack of platelets leads to an increased tendency to bleed. They decrease especially in the first two years of life. Intracranial hemorrhages may occur in the first months, which may promote motor or mental retardation. Bilaterally, all patients of the syndrome also lack the spokes. The thumb of affected individuals is present but functions only abnormally. Often, there is a radial deviation of the hand that manifests as a club hand deformity. The ulna of all TAR patients is shortened and partially bent. About one third of patients lack the humerus, which is usually also shortened and dysplastic. The joints of the elbow, shoulder and hand are restricted in their mobility. In some cases, additional changes in the blood are present. Thus, in two-thirds of the cases there are strongly elevated leukocytes. Often a cow’s milk allergy or intolerance is present, which promotes diarrhea or aggravates the thrombocytopenia. In about half of all patients, the symptoms are associated with dysplasia of the lower extremities. In particular, hip dysplasia, coxa valga, knee subluxation, or patellar dysplasia with dislocation are common symptoms. The knee may be stiffened. Foot and toe positions are often abnormal. Many of those affected also suffer from short stature or a heart defect in the sense of a tetralogy of Fallot or an atrial septal defect. In the eye, ptosis or glaucoma is often present.
Diagnosis and course of the disease
In the first months of life, physicians will observe a bleeding tendency and thrombocytopenia in TAR patients, which they must differentiate from Fanconi anemia by differential diagnosis. On radiography, TAR syndrome is manifested primarily by bilateral nonunion of the spokes and the resulting malpositions. Differentially, Holt-Oram syndrome and Roberts syndrome must also be considered in the diagnosis.Once the first two years of life have been completed, the prognosis for patients with TAR syndrome is rather favorable. In individual cases, the prognosis depends on concomitant symptoms such as the heart defect.
Complications
Several malformations occur in TAR syndrome. First and foremost, the malformations lead to a markedly increased bleeding tendency. Affected individuals suffer from severe bleeding even from very minor and slight injuries, which cannot be stopped easily. Bleeding from the gums or nose is also common and has a very negative effect on the quality of life of the affected person. Furthermore, mental retardation may occur due to TAR syndrome. Patients are very often dependent on the help of other people in their lives and are unable to perform many everyday tasks on their own. The mobility of the shoulders and hands is also significantly limited by the syndrome, as the upper arm bone is missing. Furthermore, there may be a heart defect or discomfort in the eyes. The syndrome is usually associated with a reduced life expectancy. The parents or relatives also often suffer from psychological complaints or even depression. Symptomatic treatment of TAR syndrome usually does not lead to complications. However, unfortunately, not all complaints can be completely limited in the process.
When should you see a doctor?
In most cases, the affected person with TAR syndrome is dependent on medical examination and treatment. There can be no independent cure in this case, so the affected person is always dependent on a medical diagnosis for this disease. The earlier the syndrome is detected, the better the further course of this disease usually is. Since it is a hereditary disease, there is no complete cure. If the person affected by the syndrome wishes to have children, genetic counseling can also be sought. A doctor should be consulted for TAR syndrome if the affected person suffers from severe mental retardation. As a rule, patients are dependent on the help of fellow human beings in their lives. The mobility of the affected person may also be limited by TAR syndrome, so that a visit to a doctor is necessary. It is not uncommon for the internal organs to be affected by various defects as well. Diagnosis of TAR syndrome can be made by a general practitioner or pediatrician. Further treatment requires a visit to a specialist.
Treatment and therapy
There is no causal or specific treatment for TAR syndrome. To date, only symptomatic treatments are available. Correction of the malformations cannot occur during the first years of life because of the tendency to bleed. Later in life, reconstructive surgical procedures can correct the missing spokes and multiple deformities. Essential in the first years of life is the prevention of all bleeding or hemorrhage. Thus, the goal of initial therapy is primarily to reduce significant sequelae of disease. Severe thrombocytopenias in the first years of life call for platelet transfusions. In and of itself, there is no motor developmental disorder. Neurological impairments are also rare. Mental development is unremarkable. Thus, any retardations are at most a consequence of intracranial hemorrhage, which the transfusions are designed to prevent. When the thrombocytopenia has subsided, plastic surgical treatment measures take place. These measures are accompanied by [[[physiotherapy|physiotherapeutic treatment steps]] to ensure proper motor development. In adulthood, patients are often no longer dependent on any treatment measures and lead a largely normal life with an unrestricted quality of life.
Prevention
The definitive causes of TAR syndrome have not yet been determined. For this reason, the syndrome cannot yet be prevented. However, all evidence suggests that genetic factors play a role in the syndrome. Therefore, genetic counseling of affected individuals can largely be described as a preventive measure.
Follow-up
Follow-up care for TAR syndrome depends on the type and severity of the malformations. After surgical intervention, which may be considered for mild malformations, the patient requires comprehensive follow-up care.In case of acute bleeding, immediate care in the clinic is necessary. The patient then requires a few days of rest. A final follow-up examination aims to determine further treatment measures. People suffering from TAR syndrome need to consult their doctor regularly to clarify their current state of health. Especially in the case of internal bleeding, medical complications are not always apparent to the patient. In cases of severe thrombopenia, a blood transfusion may be necessary, which takes place in the clinic and is usually associated with a follow-up consultation. In turn, the patient requires rest and sparing. Hospitalization is usually indicated. Patients suffering from TAR syndrome need a specialist. The physician in charge is usually the internist or general practitioner who is already involved in the treatment. In the case of chronic symptoms, long-term placement in a clinic is advisable. The patient should also contact a physiotherapist and other specialists. Psychological support for the patient may also be necessary.
What you can do yourself
TAR syndrome can only be treated symptomatically. The patient must watch for warning signs and inform the doctor so that a blood transfusion can be performed early. After such a transfusion, the body is weakened and it is important to pay attention to a balanced diet that supports the body in blood formation. After surgical treatment of the malformations, rest and bed rest apply. The patient must take care of the wounds according to the doctor’s instructions to avoid inflammation and other complications. In the case of deformities of the limbs, physiotherapeutic treatment may also be necessary. Affected individuals can perform physiotherapy at home and improve the coordination of the affected limbs with regular exercise. If these measures do not achieve the desired result, the doctor must be consulted. Since TAR syndrome is an extremely rare condition, a specialized medical professional must provide therapy. It is advisable to search internet forums for other sufferers, as there are few support groups for the condition. Lastly, it is important to make the necessary medical appointments to avoid serious complications. TAR syndrome requires close monitoring because of any blood transfusions.
