IllnessThrombozytopenia-Absent radius syndrome, differential diagnosis

NGS +

In TAR (thrombocytopenia-absent radius) syndrome, both radii are lacking in addition to the more or less pronounced thrombocytopenia. The latter usually occurs in infancy and becomes less severe over time. Potentially life-threatening episodes of hemorrhage can occur in the brain, for example, especially in the first year of life. Patients without massive bleedings usually have normal life expectancy and normal mental development. The severity of the skeletal problems in TAR syndrome varies among affected individuals. While the radii are almost always absent from both arms, the ulnae are sometimes only underdeveloped. In TAR syndrome, the thumbs are present, but syndactyly or clinodactyly of the fifth finger may occur. Some TAR patients also have additional skeletal abnormalities. Other symptoms may include malformations of the heart or kidneys associated with unusual facial features. About 50% of affected individuals have cow milk allergy. Mutations in the RBM8A gene cause the syndrome. Most affected individuals have a mutation in one copy of the gene and a deletion on chromosome 1 that includes the other copy of the RBM8A gene (one >200-500 kb deletion in 95% of TAR patients). Very few affected individuals have both copies of the RBM8A gene (point-) mutated. TAR syndrome is inherited in an autosomal recessive manner, with the deletions arising during egg or sperm formation or alternatively somatically during early fetal development in up to 25% of cases. Since the molecular genetic diagnostic yield reaches >95%, the clinical diagnosis is mostly confirmed.

Reference: https://www.ncbi.nlm.nih.gov/books/NBK23758/

• Alias. Radial aplasia-thrombocytopenia syndrome
• Alias: Chromosome 1q21.1 deletion syndrome, 200-KB
• Alias: Radial aplasia-amegakaryocytic thrombocytopenia
• Alias: TAR-Syndrom [Thrombocytopenia Absent Radii syndrome]
• Baller-Gerold syndrome (RECQL4)
• Duane-radial ray syndrome (SALL4)
• Holt-Oram syndrome (TBX5)
• IVIC syndrome (SALL4)
• Juberg-Hayward syndrome (ESCO2)
• RAPADILINO syndrome (RECQL4)
• Roberts-SC phocomelia syndrome (ESCO2)
• Rothmund-Thomson syndrome, type 1 (ANAPC1)
• Rothmund-Thomson syndrome, type 2 (RECQL4)
• Thrombocytopenia-absent radius syndrome (RBM8A)
• Townes-Brocks branchiootorenal-like syndrome (SALL1)
• Townes-Brocks syndrome 1 (SALL1)