Abstract
Rubinstein-Taybi syndrome (RTS) is a rare developmental disorder characterized by craniofacial dysmorphisms, broad thumbs and toes, mental and growth deficiency, and recurrent respiratory infections. RTS has been associated with CREBBP gene mutations, but EP300 gene mutations have recently been reported in 6 individuals. In the present study, the humoral immune response in 16 RTS patients with recurrent respiratory infections of possible bacterial etiology was evaluated. No significant differences between patients and 16 healthy controls were detected to explain the high susceptibility to respiratory infections: normal or elevated serum immunoglobulin levels, normal salivary IgA levels, and a good antibody response to both polysaccharide and protein antigens were observed. However, most patients presented high serum IgM levels, a high number of total B cell and B subsets, and also high percentiles of apoptosis, suggesting that they could present B dysregulation. The CREBBP/p300 family gene is extremely important for B-cell regulation, and RTS may represent an interesting human model for studying the molecular mechanisms involved in B-cell development.
Highlights
Rubinstein-Taybi syndrome (RTS), a clinically welldefined condition, is a rare developmental disorder characterized by craniofacial dysmorphisms, broad thumbs and toes, and mental and growth deficiency [1]
Concentration of serum and salivary immunoglobulins Normal or elevated serum IgG levels were observed in RTS patients
The loss of CBP in B cells leads to higher levels of IgG3 and IgM [18]. These findings suggest that the serum concentration of IgM can be regulated by activation of CREB protein when it is phosphorylated by protein kinase A and interacts with the KIX region of CBP (1921)
Summary
Rubinstein-Taybi syndrome (RTS), a clinically welldefined condition, is a rare developmental disorder characterized by craniofacial dysmorphisms, broad thumbs and toes, and mental and growth deficiency [1]. The major items to look for in RTS are a beaked nose, grimacing smile, broad thumbs and big toes, and mental retardation [4]. The main clinical problems are failure to thrive, congenital heart defects, and recurrent respiratory infections [5]. RTS has been associated with mutations of the CREB-binding protein (CREBBP or CBP) gene, located on chromosome 16p13.3 [6], which have been demonstrated in 45-56% of RTS patients [7]. Mutations of the EP300 (p300) gene, located on chromosome 22q13.3, were recently identified in six RTS patients [8,9]
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