Genotype-phenotype correlations in Rubinstein-Taybi syndrome.

Rubinstein-Taybi syndrome (RTS) is a rare multiple congenital anomaly/intellectual impairment syndrome. Loss of function in CREBBP or EP300 genes has been found in about 50% of patients with RTS. Genotype-phenotype correlations were investigated in 93 patients meeting diagnostic criteria for RTS during 2 international RTS family conferences. Mutation analysis of CREBBP was performed on all 31 coding exons and exon-intron junctions; a subset of patients had FISH analysis for large deletions. A total of 64 different variations were observed in the DNA sequence, and determined to be definitive mutations in 52 patients (56%). Mutations detected included: 10 missense mutations; 36 truncating or splice-site mutations; and 6 large deletions detectable by FISH. Fourteen patients had synonymous changes of unknown significance. The majority of mutations affected the HAT domain of CREBBP or predicted termination of the protein before the HAT region. Extensive phenotypic data were collected on each patient and analyzed to determine correlations with mutation types, that is, truncating, large deletions, single amino acid substitutions, or no CREBBP mutation. All four groups displayed the characteristic facial and thumb dysmorphology. Growth retardation in height and weight was seen more frequently in patients with no CREBBP mutation; seizure disorder was more frequent in those with CREBBP mutations. Degree of mental retardation was similar in all groups, although there was a trend toward lower IQ and autistic features in patients with large deletions. Similarity in phenotype between the groups implies that the several genes involved in causing RTS likely have effects through the same pathway.

Diagnostic analysis of the Rubinstein-Taybi syndrome: five cosmids should be used for microdeletion detection and low number of protein truncating mutations.

Rubinstein-Taybi syndrome (RTS) is a malformation syndrome characterised by facial abnormalities, broad thumbs, broad big toes, and mental retardation. In a subset of RTS patients, microdeletions, translocations, and inversions involving chromosome band 16p13.3 can be detected. We have previously shown that disruption of the human CREB binding protein (CREBBP or CBP) gene, either by these gross chromosomal rearrangements or by point mutations, leads to RTS. CBP is a large nuclear protein involved in transcription regulation, chromatin remodelling, and the integration of several different signal transduction pathways. Here we report diagnostic analysis of CBP in 194 RTS patients, divided into several subsets. In one case the mother is also suspect of having RTS. Analyses of the entire CBP gene by the protein truncation test showed 4/37 truncating mutations. Two point mutations, one 11 bp deletion, and one mutation affecting the splicing of the second exon were detected by subsequent sequencing. Screening the CBP gene for larger deletions, by using different cosmid probes in FISH, showed 14/171 microdeletions. Using five cosmid probes that contain the entire gene, we found 8/89 microdeletions of which 4/8 were 5' or interstitial. This last subset of microdeletions would not have been detected using the commonly used 3' probe RT1, showing the necessity of using all five probes.

Variation in microdeletions of the cyclic AMP-responsive element-binding protein gene at chromosome band 16p13.3 in the Rubinstein-Taybi syndrome.

Most reported microdeletions of the CREB-binding protein (CBP) gene in the Rubinstein-Taybi syndrome (RTS) were detected by fluorescence in situ hybridization (FISH) with a single cosmid probe specific to the 3' region of the gene. In order to test the hypothesis that the rate of microdeletion-positive cases would be greater if the entire gene was evaluated, we performed FISH on 66 patients with an established diagnosis of RTS, using a panel of five cosmids that span the CBP gene. Five of 66 patients had deletions by FISH (9%), consistent with those rates reported in various series that ranged between 3-25%. Among our cases, different deletions were observed; one was deleted for the 5' but not the 3' region of the CBP gene (case 055). Other deletions included a total CBP deletion extending from the 5' through the 3' region (case 017), a deletion of all but the 5' region (cases 006 and 060), and an interstitial deletion in the 3' region (case 028). Fine breakpoint mapping with additional cosmid and yeast artificial chromosome (YAC) constructs was performed on these patients. The findings of a partial 5' deletion and of interstitial deletions of the CBP gene add to the known spectrum of mutations of this gene in RTS and demonstrate the need for evaluation of the entire CBP gene region for deletions rather than only the 3' region in RTS patients. These results further suggest that the true rate of microdeletion across the CBP gene detectable by FISH has yet to be established firmly. No phenotypic differences between partial deletion, complete deletion, and nondeletion patients were observed, supporting a haploinsufficiency model for RSTS.

Instability of the patellofemoral joint in Rubinstein-Taybi syndrome.

Twenty-five (3.4%) of 732 individuals with Rubinstein-Taybi syndrome were noted to have instability of the patellofemoral joint. We believe that this is in fact an underrepresentation of the true incidence, as we were able to identify only those patients whose symptoms were most severe. These individuals typically had symptoms before or during their adolescent growth spurt, had bilateral involvement, and in some instances, ceased to ambulate because of their patellofemoral problems. A subset of these individuals underwent patellar realignment surgery, with those whose treatment did not include extensive quadriceps mobilization/quadricepsplasty having a 2.7 times higher risk of requiring revision patellar surgery. Patellofemoral instability associated with Rubinstein-Taybi syndrome demands early recognition and treatment to prevent potentially catastrophic gait disturbances.

Glaucoma and findings simulating glaucoma in the Rubinstein-Taybi syndrome.

Information is reviewed on the ophthalmologic findings in 614 individuals with Rubinstein-Taybi syndrome (RTS). The data were collected from the world literature, from communication with colleagues and with families of individuals with RTS, and from personal observations. Particular emphasis is given in this article to the association of RTS with glaucoma and five other findings that may be confused with glaucoma (corneal lesions, megalocornea, colobomatous or cystic optic nerve, excavation of papilla, and large cup-to-disc ratio). A case report is presented including autopsy results on a 5-year-old black female with RTS, corneal lesions, colobomas of the optic nerves, and normal intraocular pressure.

Tumors in Rubinstein-Taybi syndrome.

The 14 tumors reported in Rubinstein-Taybi syndrome since 1989, when added to the 22 previously reported, are beginning to show a pattern of neural and developmental tumors, especially of the head, which is malformed in the syndrome. Among the neoplasms were 12 of the nervous system: 2 each of oligodendroglioma, medulloblastoma, neuroblastoma, and benign meningioma, a pheochromocytoma, and 3 other benign tumors; 2 of nasopharyngeal rhabdomyosarcoma; and 1 each of leiomyosarcoma, seminoma, and embryonal carcinoma. Among the other benign tumors were an odontoma, a choristoma, a dermoid cyst, and 2 pilomatrixomas.

Broad thumb-hallux (Rubinstein-Taybi) syndrome 1957-1988.

This presentation records the early history of the description of the broad thumb-hallux syndrome and attempts to update the current state of knowledge about this syndrome. Information was collected and reviewed on 571 individuals from the world literature, from communications with colleagues and families of affected individuals, and from personal observation. The diagnosis was established in most cases by confirming the concurrence of the constellation of major diagnostic criteria, including broad short terminal phalanges of the thumbs and halluces, with or without angulation deformity; characteristic facial appearance with beaked or straight nose, antimongoloid slant of palpebral fissures, apparent or clinical hypertelorism and grimacing smile; stature and head circumference (OFC) below 50th centile; mental, motor, social, and language retardation; stiff awkward gait; and incomplete or delayed descent of testes in males. Information on associated clinical factors, familial occurrence, and cytogenetic findings is presented.

Keloids and neoplasms in the Rubinstein-Taybi syndrome.

In a series of 574 individuals with the Rubinstein-Taybi syndrome, 28 had keloids, and 19 had one or more neoplasms. The array of malignant neoplasms does not suggest an etiology or pathogenesis in common. One possible exception is that four cases of leukemia were observed. When the data for malignant and benign neoplasms were combined, at least nine of the 22 could have arisen from developmental errors. The apparent excess of keloid formation indicates overreaction to mild injury, with no known relevance to neoplasia but of potential interest in future studies of scar formation.

Surgical treatment of the thumb in the Rubinstein-Taybi syndrome.

In a review of 530 individuals with Rubinstein-Taybi syndrome, 182 (34%) were found to have thumbs in severe radial angulation ("hitch-hiker thumbs"), which prevented opposition and functional gripping strength. Surgery has been performed on 35 thumbs (from 20 patients), usually to correct a delta phalanx deformity. The preferred approach was a closing wedge osteotomy, with a Z-plasty on the concave side to straighten the thumb. In eight and possibly 11 of the 35 thumbs, the angulation deformity or stiffness recurred, emphasizing the importance of proper and careful surgery. We conclude that surgical correction of the deformity is best done before the age of two, so that the thumb is functional during the initial development of hand-eye coordination. Deviation persisting at the age of ten can be corrected by fusing the metacarpophalangeal joint.

Water intoxication secondary to feeding mismanagement. A preventable form of familial seizure disorder in infants.

Water intoxication with seizures secondary to excessive fluid ingestion occurred in four apparently healthy infants in two families; we also review five previously reported cases.