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TAR syndrome
What are the symptoms?
All individuals with TAR have low platelets but often as they grow older, it becomes less of a problem and affected individuals can outgrow the risk of bleeding related to low platelets. About ninety per cent of individuals with TAR are symptomatic during the first year of life with easy bruising, bleeding from the GI tract or even bleeding into the brain. The level of platelets will fall and rise throughout low platelet episodes. A normal platelet count is greater than two hundred thousand platelets per millilitres squared of blood. Individuals with TAR may have less than ten thousand platelets per millilitres squared when they are having severe episodes.
In addition to problems with platelets, some individuals with TAR may make too many white cells at times. This is termed a leukaemoid reaction and should not be confused with leukaemia in the sense of being a malignancy. Leukaemoid reaction most often occurs in early infancy along with low platelets in a very sick child.
Occasionally, the bone marrow makes too much of one type of blood cell called the eosinophil. The eosinophil is a white blood cell reddish granules. It is usually associated with allergies and asthma. Many individuals with TAR seem to have an allergy to cow's milk and they will usually be found to have an increase in the eosinophils.
Individuals with TAR often have anaemia (anemia - US) or low red cells. This can be because of bleeding but it is thought that during the first year of life, fewer red cells are made than in the average individual. Affected individuals tend to outgrow anaemia.
The consistent skeletal feature of TAR is absence of the radius but presence of the thumb. The legs may be affected as well. There can be dislocation of the hips so that the head of the femur doesn't sit properly into the hip socket. There can be abnormalities of the knees leading to bending abnormally one way or the other, loose kneecaps, or the bones of the knee slipping on each other. Occasionally the bones of the knee are even fused. Frequently there are abnormalities of toe positioning with 'scrambling' of the toes and occasionally there is some puffiness to the foot.
It would appear the more severely involved the upper limb is, the more likely the lower limbs are to be involved as well. However, if the lower limb is involved, it appears that all five toes and a normal foot is usually seen. At least twenty per cent of affected individuals have significant lower limb involvement.
Minor abnormalities of the ribs, the spine or the jaw can be seen.
Most individuals with TAR are shorter than other family members. No important endocrine abnormalities or growth hormone deficiency have been seen in TAR.
The most frequent other type of anomaly found in individuals with TAR is a hole in the heart. About thirty per cent of affected individuals have some kind of structural abnormality of the heart. This can lead to complications in heart surgery due to the low platelets. However, there are a number of individuals who have had quite complicated heart surgery and, with the aid of platelet transfusions, have done extremely well.
Learning disability can be seen in TAR but this appears to be in individuals who have had a bleed into the brain.
Most affected individuals have bruising at birth. Many develop cow's milk allergy and diarrhoea in infancy. Diarrhoeal illness seems to precipitate low platelets and is of real concern. During the first year of life, there seems to be episodes of low platelets. It is important to avoid cow's milk if it is an irritant. It is also important to avoid viral illnesses particularly gastroenterological ones for the first two years of life.
Background
| Inheritance patterns and prenatal diagnosis 
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