Rubinstein Taybi syndrome occurs only with a frequency of 1 in 300,000 births, but is fairly commonly seen in mental retardation clinics (about 1 in 600).
The typical features are broad malformed thumbs and big toes as well as typical facial abnormalities and mental retardation. It is due to a spontaneous deletion of part of chromosome 16(16p13-) , thanks to www.sandoz.sk for this image) leading to these multiple abnormal fetal developments.
Signs and symptoms:
Facial deformities include an underdeveloped small maxilla with a narrow palate. Typically there are low set ears and often malformed. Sometimes there is a typical talon cusp malformation in one or more incisor teeth as depicted in this image. This person shown in the link (thanks to www.nature.com for the images) had only minimal features of Rubinstein Taybi syndrome, but the typical dental abnormality triggered a chromosomal work-up and confirmed the presence of this syndrome in this case. There are deformities of thumb and big toe (thanks to www.nature.com for the images) with a wide base and angulations towards the fingers or toes. Syndactyly and polydactyly also exists in some cases. Several eye deformities are also common like congenital glaucoma, retinal abnormalities and strabismus.
The child has growth retardation and as adults they do not grow taller than 58 to 60 inches. The child has speech difficulties and a muscle weakness problem (hypotonia). There are feeding problems. In girls hirsutism is common, in boys cryptorchidism. Mental retardation is severe with an intelligence quotient between 30 and 80, with 50% or more having an IQ of 50. Joint hypermobility poses problems with patellofemoral instability and frequent patellar dislocations. Cardiac malformations are common with ventricular septal defects, atrial septal defects, patent ductus arteriosus etc. There is a high sensitivity to succinylcholine, which is used generally with intubation general anesthesia during surgeries and this can cause life threatening cardiac arrhythmias.
Prognosis
The prognosis depends on the mix of congenital conditions present. Attention to detail by the cardiologist, neurologist, pediatrician, orthopedic surgeon and ophthalmologist will give the baby the best chance of survival. However, the limiting conditions are any cardiac malformation, feeding problems with possible aspiration pneumonia and subsequent infection and possible blindness, if the congenital eye abnormality is serious.
References:
1. Deletion of chromosome 16(16p13-): http://ghr.nlm.nih.gov/gene=crebbp
2. Goldman: Cecil Medicine, 23rd ed. Copyright © 2007 Saunders, An Imprint of Elsevier: Chromosomal disorders.
