Increased fracture risk and low bone mineral density in patients with loeys-dietz syndrome.

Loeys-Dietz syndrome is a recently recognized connective tissue disorder with widespread systemic involvement. Little is known about its skeletal phenotype. Our goal was to investigate the risk of fracture and incidence of low bone mineral density in patients with Loeys-Dietz syndrome. We performed a cross-sectional, descriptive, survey-based study with subsequent chart review from July 2011 to April 2012. Fifty-seven patients (26 men, 31 women) with Loeys-Dietz syndrome confirmed by genetic testing completed the survey (average age, 25.3 years; range, 0.9-79.6 years). There were a total of 51 fractures (33 patients): 35 fractures in the upper extremities, 14 in the lower extremities, and two in the spine. Fourteen patients (24.6%) reported two or more fractures. There was a 50% risk of fracture by age 14 years. The incidence of any fracture in this cohort was 3.86 per 100 person-years. Seventeen patients had dual-energy X-ray absorptiometry scans available for review, 11 (64.7%) of whom had at least one fracture. Thirteen included lumbar spine absorptiometry reports; eight (61.5%) indicated low or very low bone mineral density. In the left hip, ten of 14 participants (71.4%) had low or very low bone mineral density. In the left femoral neck, nine of 13 participants (69.2%) had low or very low bone mineral density. The lowest Z- and T-scores were not associated with an increased number of fractures. Patients with Loeys-Dietz syndrome have a high risk of fracture and a high incidence of low bone mineral density.

Causes and histopathology of ascending aortic disease in children and young adults.

BACKGROUND: Ascending aortic diseases (aneurysms, dissections, and stenosis) and associated aortic valve disease are rare but important causes of morbidity and mortality in children and young adults. Certain genetic causes, such as Marfan syndrome and congenital bicuspid aortic valve disease, are well known. However, other rarer genetic and nongenetic causes of aortic disease exist. METHODS: We performed an extensive literature search to identify known causes of ascending aortic pathology in children and young adults. We catalogued both aortic pathologies and other defining systemic features of these diseases. RESULTS: We describe 17 predominantly genetic entities that have been associated with thoracic aortic disease in this age group. CONCLUSIONS: While extensive literature on the common causes of ascending aortic disease exists, there is a need for better histologic documentation of aortic pathology in rarer diseases.

Musculoskeletal findings of Loeys-Dietz syndrome.

BACKGROUND: Loeys-Dietz syndrome is a recently recognized multisystemic disorder caused by mutations in the genes encoding the transforming growth factor-beta receptor. It is characterized by aggressive aneurysm formation and vascular tortuosity. We report the musculoskeletal demographic, clinical, and imaging findings of this syndrome to aid in its diagnosis and treatment. METHODS: We retrospectively analyzed the demographic, clinical, and imaging data of sixty-five patients with Loeys-Dietz syndrome seen at one institution from May 2007 through December 2008. RESULTS: The patients had a mean age of twenty-one years, and thirty-six of the sixty-five patients were less than eighteen years old. Previous diagnoses for these patients included Marfan syndrome (sixteen patients) and Ehlers-Danlos syndrome (two patients). Spinal and foot abnormalities were the most clinically important skeletal findings. Eleven patients had talipes equinovarus, and nineteen patients had cervical anomalies and instability. Thirty patients had scoliosis (mean Cobb angle [and standard deviation], 30 degrees +/- 18 degrees ). Two patients had spondylolisthesis, and twenty-two of thirty-three who had computed tomography scans had dural ectasia. Thirty-five patients had pectus excavatum, and eight had pectus carinatum. Combined thumb and wrist signs were present in approximately one-fourth of the patients. Acetabular protrusion was present in approximately one-third of the patients and was usually mild. Fourteen patients had previous orthopaedic procedures, including scoliosis surgery, cervical stabilization, clubfoot correction, and hip arthroplasty. Features of Loeys-Dietz syndrome that are important clues to aid in making this diagnosis include bifid broad uvulas, hypertelorism, substantial joint laxity, and translucent skin. CONCLUSIONS: Patients with Loeys-Dietz syndrome commonly present to the orthopaedic surgeon with cervical malformations, spinal and foot deformities, and findings in the craniofacial and cutaneous systems. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

Whole-genome sequencing of a single proband together with linkage analysis identifies a Mendelian disease gene.

Although more than 2,400 genes have been shown to contain variants that cause Mendelian disease, there are still several thousand such diseases yet to be molecularly defined. The ability of new whole-genome sequencing technologies to rapidly indentify most of the genetic variants in any given genome opens an exciting opportunity to identify these disease genes. Here we sequenced the whole genome of a single patient with the dominant Mendelian disease, metachondromatosis (OMIM 156250), and used partial linkage data from her small family to focus our search for the responsible variant. In the proband, we identified an 11 bp deletion in exon four of PTPN11, which alters frame, results in premature translation termination, and co-segregates with the phenotype. In a second metachondromatosis family, we confirmed our result by identifying a nonsense mutation in exon 4 of PTPN11 that also co-segregates with the phenotype. Sequencing PTPN11 exon 4 in 469 controls showed no such protein truncating variants, supporting the pathogenicity of these two mutations. This combination of a new technology and a classical genetic approach provides a powerful strategy to discover the genes responsible for unexplained Mendelian disorders.

Aneurysm syndromes caused by mutations in the TGF-beta receptor.

BACKGROUND: The Loeys-Dietz syndrome is a recently described autosomal dominant aortic-aneurysm syndrome with widespread systemic involvement. The disease is characterized by the triad of arterial tortuosity and aneurysms, hypertelorism, and bifid uvula or cleft palate and is caused by heterozygous mutations in the genes encoding transforming growth factor beta receptors 1 and 2 (TGFBR1 and TGFBR2, respectively). METHODS: We undertook the clinical and molecular characterization of 52 affected families. Forty probands presented with typical manifestations of the Loeys-Dietz syndrome. In view of the phenotypic overlap between this syndrome and vascular Ehlers-Danlos syndrome, we screened an additional cohort of 40 patients who had vascular Ehlers-Danlos syndrome without the characteristic type III collagen abnormalities or the craniofacial features of the Loeys-Dietz syndrome. RESULTS: We found a mutation in TGFBR1 or TGFBR2 in all probands with typical Loeys-Dietz syndrome (type I) and in 12 probands presenting with vascular Ehlers-Danlos syndrome (Loeys-Dietz syndrome type II). The natural history of both types was characterized by aggressive arterial aneurysms (mean age at death, 26.0 years) and a high incidence of pregnancy-related complications (in 6 of 12 women). Patients with Loeys-Dietz syndrome type I, as compared with those with type II, underwent cardiovascular surgery earlier (mean age, 16.9 years vs. 26.9 years) and died earlier (22.6 years vs. 31.8 years). There were 59 vascular surgeries in the cohort, with one death during the procedure. This low rate of intraoperative mortality distinguishes the Loeys-Dietz syndrome from vascular Ehlers-Danlos syndrome. CONCLUSIONS: Mutations in either TGFBR1 or TGFBR2 predispose patients to aggressive and widespread vascular disease. The severity of the clinical presentation is predictive of the outcome. Genotyping of patients presenting with symptoms like those of vascular Ehlers-Danlos syndrome may be used to guide therapy, including the use and timing of prophylactic vascular surgery.

Infantile restrictive cardiomyopathy resulting from a mutation in the cardiac troponin T gene.

Here we report the first infantile case of restrictive cardiomyopathy caused by a de novo mutation of the cardiac troponin T gene. The patient presented with an apparent life-threatening event. She developed malignant arrhythmias and hemodynamic instability, requiring initial rescue support with extracorporeal membrane oxygenation, and subsequently underwent insertion of a biventricular assist device (VAD). She successfully received an orthotopic heart transplant 172 days after VAD implantation.