Functional biology of the Steel syndrome founder allele and evidence for clan genomics derivation of COL27A1 pathogenic alleles worldwide.

Previously we reported the identification of a homozygous COL27A1 (c.2089G>C; p.Gly697Arg) missense variant and proposed it as a founder allele in Puerto Rico segregating with Steel syndrome (STLS, MIM #615155); a rare osteochondrodysplasia characterized by short stature, congenital bilateral hip dysplasia, carpal coalitions, and scoliosis. We now report segregation of this variant in five probands from the initial clinical report defining the syndrome and an additional family of Puerto Rican descent with multiple affected adult individuals. We modeled the orthologous variant in murine Col27a1 and found it recapitulates some of the major Steel syndrome associated skeletal features including reduced body length, scoliosis, and a more rounded skull shape. Characterization of the in vivo murine model shows abnormal collagen deposition in the extracellular matrix and disorganization of the proliferative zone of the growth plate. We report additional COL27A1 pathogenic variant alleles identified in unrelated consanguineous Turkish kindreds suggesting Clan Genomics and identity-by-descent homozygosity contributing to disease in this population. The hypothesis that carrier states for this autosomal recessive osteochondrodysplasia may contribute to common complex traits is further explored in a large clinical population cohort. Our findings augment our understanding of COL27A1 biology and its role in skeletal development; and expand the functional allelic architecture in this gene underlying both rare and common disease phenotypes.

Clinical and radiological distinction between spondylothoracic dysostosis (Lavy-Moseley syndrome) and spondylocostal dysostosis (Jarcho-Levin syndrome).

In 1938, Saul Jarcho and Paul Levin from Johns Hopkins Hospital reported cases of thoracic insufficiency due to vertebral and rib anomalies. Nearly 30 years later, in 1966, Norman Lavy and associates from Indiana University reported a similar syndrome in a family from Puerto Rico. Lavy's description was followed by a report by John E. Moseley from New York City, where the name spondylothoracic dysplasia (dysostosis) was first used. For more than half a century, there has been confusion regarding the distinction between these two phenotypically similar syndromes that cause thoracic insufficiency. Spondylocostal dysostosis (SCD), or Jarcho-Levin syndrome, causes mild to moderate respiratory insufficiency, is panethnic and has been linked to genes such as DLL3, which is known to be associated with the Notch pathway. In contrast, spondylothoracic dysostosis (STD), or Lavy-Moseley syndrome, results in more severe respiratory compromise, is largely linked to Puerto Rican cohorts and is thought to be associated to the MESP2 gene, also a Notch pathway gene. Long-term studies of Puerto Rican cohorts with STD contradicts the previously held belief that individuals affected with STD have markedly diminished life expectancy with as many as 25% surviving into later childhood and adult life.

Steel syndrome: dislocated hips and radial heads, carpal coalition, scoliosis, short stature, and characteristic facial features.

BACKGROUND: A syndrome of children with short stature, bilateral hip dislocations, radial head dislocations, carpal coalitions, scoliosis, and cavus feet in Puerto Rican children, was reported by Steel et al in 1993. The syndrome was described as a unique entity with dismal results after conventional treatment of dislocated hips. The purpose of this study is to reevaluate this patient population with a longer follow-up and delineate the clinical and radiologic features, treatment outcomes, and the genetic characteristics. METHODS: This is a retrospective cohort study of 32 patients in whom we evaluated the clinical, imaging data, and genetic characteristics. We compare the findings and quality of life in patients with this syndrome who have had attempts at reduction of the hips versus those who did not have the treatment. RESULTS: Congenital hip dislocations were present in 100% of the patients. There was no attempt at reduction in 39% (25/64) of the hips. In the remaining 61% (39/64), the hips were treated with a variety of modalities fraught with complications. Of those treated, 85% (33/39) remain dislocated, the rest of the hips continue subluxated with acetabular dysplasia and pain. The group of hips that were not treated reported fewer complaints and limitation in daily activities compared with the hips that had attempts at reduction. CONCLUSIONS: Steel syndrome is a distinct clinical entity characterized by short stature, bilateral hip and radial head dislocation, carpal coalition, scoliosis, cavus feet, and characteristic facial features with dismal results for attempts at reduction of the hips. LEVEL OF EVIDENCE: Prognostic Study Level II.

Natural history of thoracic insufficiency syndrome: a spondylothoracic dysplasia perspective.

BACKGROUND: Spondylothoracic dysplasia is a condition in which bilateral chest wall deformity due to costovertebral rib fusion with shortening of the thoracic spine results in severe thoracic insufficiency syndrome and early death. Little is known about the long-term respiratory natural history of this disorder and the specific anatomic deformity. METHODS: We conducted a multicenter prospective and retrospective study of patients with spondylothoracic dysplasia. Medical evaluations, respiratory history, physical examination findings, radiographs, computed tomographic scans, and pulmonary function tests were studied. Anatomic, radiographic, and functional parameters for the disorder were established to determine the natural history of the thoracic insufficiency syndrome. RESULTS: Twenty-eight patients were identified. Eight patients had died in the neonatal period, and twenty were evaluated (eleven prospectively and nine retrospectively). The survivors were doing well clinically, but the average spirometric values were 27.9% of the predicted normal value for the forced vital capacity (FVC), 29.5% of the predicted normal value for the forced expiratory volume in the first second (FEV1), and 0.92 for the FEV1/FVC ratio, demonstrating a severe restrictive respiratory pattern. The computed tomographic scan lung volumes were an average of 28% of the expected values for age and gender. The thorax was stiff from rib fusion and was severely shortened posteriorly, averaging 24.2% of the predicted normal length. The thoracic spine was predominantly composed of block vertebrae, whereas in the lumbar region there were multiple hemivertebrae. Minimal scoliosis was seen, and there were no neurological deficits. CONCLUSIONS: Spondylothoracic dysplasia has a unique pathoanatomy of volume depletion deformity of the thorax with chest wall stiffness, resulting in thoracic insufficiency syndrome. Clinical tolerance of the restrictive lung disease in this disorder is impressive, but no clear reason has yet been identified for the clinical pulmonary health in the face of severe restrictive lung disease. Patients who survive infancy show no progression of congenital anomalies and can have a good quality of life. This disease may serve as a model of the natural history of thoracic insufficiency syndrome due to growth inhibition of the thoracic spine either as a result of congenital causes or secondary to surgical fusion early in life.

Controversies surrounding Jarcho-Levin syndrome.

PURPOSE OF THE REVIEW: Jarcho-Levin syndrome is an eponym that has been used to describe a variety of clinical phenotypes consisting of short-trunk dwarfism associated with rib and vertebral anomalies. This admixture of phenotypes under Jarcho-Levin syndrome has allowed some confusion in terms of phenotype, prognosis, and mortality. In the past 2 years, few papers have provided more insight into the clinical diagnosis, prognosis, and management of patient with these phenotypes. RECENT FINDINGS: Recently molecular, clinical, and radiologic data have allowed further characterization of these phenotypes. Based on these findings, we have divided these phenotypes into spondylothoracic dysplasia and spondylocostal dysostosis. SUMMARY: A better understanding of the distinct phenotypes under Jarcho-Levin syndrome will help clinicians to understand the pathological factors of the disease, establish mode of inheritance, provide adequate genetic counseling, prognosis, molecular diagnosis, and clinical management recommendations.