Myhre syndrome: Clinical features and restrictive cardiopulmonary complications

Myhre syndrome in adulthood: clinical variability and emerging genotype-phenotype correlations

Myhre syndrome (MS, MIM 139210) is a rare multisystemic disorder caused by recurrent pathogenic missense variants in SMAD4. The clinical features have been mainly documented in childhood and comprise variable neurocognitive development, recognizable craniofacial features, a short stature with a pseudo-muscular build, hearing loss, thickened skin, joint limitations, diverse cardiovascular and airway manifestations, and increased fibrosis often following trauma or surgery. In contrast, adults with MS are underreported obscuring potential clinical variability. Here, we describe 24 adults with MS, including 17 diagnosed after the age of 18 years old, and we review the literature on adults with MS. Overall, our cohort shows a milder phenotype as well as lower mortality rates compared to what has been published in literature. Individuals with a codon 500 variant in SMAD4 present with a more pronounced neurodevelopmental and systemic phenotype. However, in contrast to the literature, we observe cardiovascular abnormalities in individuals with the p.(Arg496Cys) variant. In addition, we describe scoliosis as a new manifestation and we report fertility in two additional males with the p.(Arg496Cys). In conclusion, our study contributes novel insights into the clinical variability of MS and underscores the importance of variant-specific considerations, and we provide recommendations for the management of MS in adulthood.

TPPU_DSF: A Web Application to Calculate Thermodynamic Parameters Using DSF Data

Here we present TPPU_DSF (https://maciasnmr.net/tppu_dsf/). This is a free and open-source web application that opens, converts, fits, and calculates the thermodynamic parameters of protein unfolding from standard differential scanning fluorimetry (DSF) data in an automated manner. The software has several applications. In the context of screening compound libraries for protein binders, obtaining thermodynamic parameters provides a more robust approach to detecting hits than the changes in the melting temperature (Tm) alone, thereby helping to increase the number of positive hits in screening campaigns. Moreover, changes in ΔGuo indicate protein response to binding at lower compound concentrations than those in the Tm, thereby reducing the costs associated with the amounts of protein and compounds required for the assays. Also, by adding thermodynamic information to the Tm comparison, the software can contribute to the optimization of protein constructs and buffer conditions, a common practice before structural and functional projects.

Emergence of the natural history of Myhre syndrome: 47 patients evaluated in the Massachusetts General Hospital Myhre Syndrome Clinic (2016-2023)

Myhre syndrome is an increasingly diagnosed ultrarare condition caused by recurrent germline autosomal dominant de novo variants in SMAD4. Detailed multispecialty evaluations performed at the Massachusetts General Hospital (MGH) Myhre Syndrome Clinic (2016-2023) and by collaborating specialists have facilitated deep phenotyping, genotyping and natural history analysis. Of 47 patients (four previously reported), most (81%) patients returned to MGH at least once. For patients followed for at least 5 years, symptom progression was observed in all. 55% were female and 9% were older than 18 years at diagnosis. Pathogenic variants in SMAD4 involved protein residues p.Ile500Val (49%), p.Ile500Thr (11%), p.Ile500Leu (2%), and p.Arg496Cys (38%). Individuals with the SMAD4 variant p.Arg496Cys were less likely to have hearing loss, growth restriction, and aortic hypoplasia than the other variant groups. Those with the p.Ile500Thr variant had moderate/severe aortic hypoplasia in three patients (60%), however, the small number (n = 5) prevented statistical comparison with the other variants. Two deaths reported in this cohort involved complex cardiovascular disease and airway stenosis, respectively. We provide a foundation for ongoing natural history studies and emphasize the need for evidence-based guidelines in anticipation of disease-specific therapies.

Myhre syndrome: expanding its paediatric phenotypic spectrum

Myhre syndrome is a rare disease secondary to pathogenic variants in SMAD4 gene. It is a multisystem disease characterised by short stature, deafness, joint stiffness, craniofacial dysmorphism, and potential cardiac manifestations. Herein, we report two new paediatric cases of Myhre syndrome who, additionally, presented with mid-aortic syndrome. This confirms and extends the scarce reports describing the association between these two entities.

Prenatal diagnosis of Myhre syndrome with a heterozygous pathogenic variant in SMAD4 gene presented with thick nuchal translucency and cardiac abnormalities

Prenatal testing was performed in a 39-year-old Chinese pregnant woman referred for increased nuchal translucency measuring 5.7 mm. Non-invasive prenatal testing and SNP array study on amniotic fluid samples were normal. Whole exome sequencing (WES) was initiated further as the fetus had pericardial effusion of 1.2 mm, thickened myocardium over the right ventricular lateral wall and aberrant right subclavian artery. A detailed fetal echocardiogram also revealed persistent left superior vena cava and dilated coronary sinus at 20 weeks. From whole exome sequencing of the trio, a de novo heterozygous variant NM_005359.5(SMAD4): c.1499T>C (p.Ile500Thr) was detected. This pathogenic variant has been reported in the postnatal case cohort of Myhre syndrome. This condition is characterized by facial dysmorphism, intellectual disability, hearing loss, skeletal abnormalities and potential life threatening respiratory or cardiovascular manifestations. Termination of pregnancy was performed at 23 weeks. Small chins, pre-axial polydactyly, brachydactyly and clinodactyly were noted in the abortus. Ultrasound findings of increased nuchal translucency, thickened myocardium and pericardial effusion prompted further genetic evaluation for the prenatal diagnosis of Myhre syndrome by whole exome sequencing.

A newborn male with Myhre syndrome, hearing loss, and complete syndactyly of fingers 3-4

BACKGROUND

Myhre syndrome is a rare multisystem genetic disorder that is caused by de novo heterozygous gain-of-function variants in SMAD4. Patients with Myhre syndrome exhibit several phenotypes at different ages such as small size, autism, developmental delay, left-sided heart defects, and hearing loss and often have a characteristic facial appearance. The early clinical diagnosis of Myhre syndrome remains a major challenge, particularly in the first year of life.

METHODS

A Chinese male infant with syndactyly of fingers, hypertelorism, short palpebral fissures, and short philtrum was enrolled into the ENT department of the Chinese PLA General Hospital. Whole exome sequencing analysis was used to detect the disease-causing variant. A literature review of Myhre syndrome was also performed.

RESULTS

A recurrent de novo missense variant c.1498A > G p.I500V(p. Ile500Val) in SMAD4 was detected confirming the clinical diagnosis of Myhre syndrome at the age of 38 days. The infant appears to be the youngest reported case of Myhre syndrome. At 23-month follow-up, the affected infant has dysmorphic facial features, growth retardation, and previously undescribed complete syndactyly. Review the literatures noted several common features in Myhre syndrome patients including hearing loss (72.7%), characteristic facial features (26.0%-54.5%), finger and toe abnormalities (3.9%-48.1%), short stature (45.5%), and respiratory (30.0%) and cardiovascular problems (65.0%).

CONCLUSIONS

Clinicians should have a low threshold to perform genetic testing on patients with features suggesting Myhre syndrome even in the first year of life. Although some individuals with Myhre syndrome have normal hearing, early onset or progressive hearing loss usually occur in one or both ears in most patients, with remarkable phenotypic heterogeneity. Syndactyly may be minor such as typical 2-3 toe involvement, or more complicated as was observed in our patient.

Mid-aortic Syndrome in a Pediatric Cohort

Mid-aortic syndrome (MAS) is an uncommon condition characterized by severe narrowing of the abdominal aorta, usually involving visceral and renal arteries. Most patients are asymptomatic and typically present with incidental hypertension which might evolve into end-organ damage if untreated. Our aim was to review 8 new pediatric MAS cases. A retrospective observational study of all pediatric patients with MAS diagnosis (April 1992-November 2021) was conducted. Patients underwent systematic evaluation (medical and family history; 12-lead electrocardiogram; echocardiogram; angiography and/or computed tomography or magnetic resonance angiography). 8 pediatric patients with MAS were included. Median age at diagnosis was 2.6 [0.2-4.7] years; median follow-up time was 8.6 [6.6-10.0] years. 6/8 patients presented with incidental hypertension, 1/8 with heart murmur, and 1/8 with heart failure symptoms. All patients were on antihypertensive treatment. 1/8 patients underwent surgery and 7/8 an endovascular treatment. At the end of the study period, among the 6 patients that underwent a successful endovascular procedure, 2 achieved good blood pressure (BP) control, 2 acceptable BP control, 1 stage 1 hypertension and, another, stage 2 hypertension. There was 1 death during follow-up. BP monitoring in pediatric patients is crucial for early recognition of MAS. Treatment should be based on the individual clinical characteristics of patients with careful planning of surgical revascularisation, if possible, after adult growth is completed. Our study demonstrates that endovascular treatment might be a good alternative to surgery. Nevertheless, further trials with larger sample size and longer-term follow-up are required to determine the best treatment approach.

Review of the Pathologic Characteristics in Myhre Syndrome: Gain-of-Function Pathogenic Variants in SMAD4 cause a Multisystem Fibroproliferative Response

Background: Myhre syndrome, caused by pathogenic variants in SMAD4, is characterized by compact body habitus with short stature, distinctive craniofacial appearance, stiff skin, cardiovascular abnormalities (valve stenosis, coarctation, hypoplasia, or stenosis of aorta), effusions of potential spaces (pericardium, pleura, peritoneum), restricted movement of the joints (including thorax), and hearing loss. Lung and airway disease has been reported, but not always well-defined, to include interstitial lung disease, large airway obstruction, and pulmonary arterial hypertension. Excessive fibroproliferation of tissues especially following trauma or surgical instrumentation has been recognized, although these may also present spontaneously. Method: We report the pathologic features of 1 new patient with progressive choanal stenosis, and 22 literature cases, including the expanded history of 5 patients (3 who died). Results: Examination of patient tissues documents cellular fibroproliferation and deposition of excessive extracellular matrix explaining some of the observed clinical features of Myhre syndrome. Conclusion: Excessive fibrosis is noted in multiple tissues, especially heart, lung, and upper and lower airways. Our research provides the first systematic review to provide a knowledge base of gross and pathologic findings in Myhre syndrome.

Natural history of Myhre syndrome

Background

Myhre syndrome (MS) is a rare genetic disease characterized by skeletal disorders, facial features and joint limitation, caused by a gain of function mutation in SMAD4 gene. The natural history of MS remains incompletely understood.

Methods

We recruited in a longitudinal retrospective study patients with molecular confirmed MS from the French reference center for rare skeletal dysplasia. We described natural history by chaining data from medical reports, clinical data warehouse, medical imaging and photographies.

Results

We included 12 patients. The median age was 22 years old (y/o). Intrauterine and postnatal growth retardation were consistently reported. In preschool age, neurodevelopment disorders were reported in 80% of children. Specifics facial and skeletal features, thickened skin and joint limitation occured mainly in school age children. The adolescence was marked by the occurrence of pulmonary arterial hypertension (PAH) and vascular stenosis. We reported for the first time recurrent strokes from the age of 26 y/o, caused by a moyamoya syndrome in one patient. Two patients died at late adolescence and in their 20 s respectively from PAH crises and mesenteric ischemia.

Conclusion

Myhre syndrome is a progressive disease with severe multisystemic impairement and life-threathning complication requiring multidisciplinary monitoring.

Cardiomyopathies in Children and Systemic Disorders When Is It Useful to Look beyond the Heart?

Cardiomyopathy (CMP) is a rare disease in the pediatric population, with a high risk of morbidity and mortality. The genetic etiology of CMPs in children is extremely heterogenous. These two factors play a major role in the difficulties of establishing standard diagnostic and therapeutic protocols. Isolated CMP in children is a frequent finding, mainly caused by sarcomeric gene variants with a detection rate that can reach up to 50% of analyzed cohorts. Complex multisystemic forms of pediatric CMP are even more heterogenous. Few studies in literature take into consideration this topic as the main core since it represents a rarity (systemic CMP) within a rarity (pediatric population CMP). Identifying etiology in this cohort is essential for understanding prognosis, risk stratification, eligibility to heart transplantation and/or mechanical-assisted procedures, preventing multiorgan complications, and relatives' recurrence risk calculation. The previous points represent a cornerstone in patients' empowerment and personalized medical care approach. The aim of this work is to propose a new approach for an algorithm in the setting of the diagnostic framework of systemic pediatric CMP. On the other hand, during the literature review, we noticed a relatively common etiologic pattern in some forms of complex/multisystem CMP. In other words, certain syndromes such as Danon, Vici, Alström, Barth, and Myhre syndrome share a common pathway of directly or indirectly defective "autophagy" process, which appears to be a possible initiating/triggering factor for CMPs. This conjoint aspect could be important for possible prognostic/therapeutic implications in this category of patients. However, multicentric studies detailed functional and experimental models are needed prior to deriving conclusions.

Expanded cardiovascular phenotype of Myhre syndrome includes tetralogy of Fallot suggesting a role for SMAD4 in human neural crest defects

Tetralogy of Fallot (ToF) can be associated with a wide range of extracardiac anomalies, with an underlying etiology identified in approximately 10% of cases. Individuals affected with Myhre syndrome due to recurrent SMAD4 mutations frequently have cardiovascular anomalies, including congenital heart defects. In addition to two patients in the literature with ToF, we describe five additional individuals with Myhre syndrome and classic ToF, ToF with pulmonary atresia and multiple aorto-pulmonary collaterals, and ToF with absent pulmonary valve. Aorta hypoplasia was documented in one patient and suspected in another two. In half of these individuals, postoperative cardiac dysfunction was thought to be more severe than classic postoperative ToF repair. There may be an increase in right ventricular pressure, and right ventricular dysfunction due to free pulmonic regurgitation. Noncardiac developmental abnormalities in our series and the literature, including corectopia, heterochromia iridis, and congenital miosis suggest an underlying defect of neural crest cell migration in Myhre syndrome. We advise clinicians that Myhre syndrome should be considered in the genetic evaluation of a child with ToF, short stature, unusual facial features, and developmental delay, as these children may be at risk for increased postoperative morbidity. Additional research is needed to investigate the hypothesis that postoperative hemodynamics in these patients may be consistent with restrictive myocardial physiology.

Multilevel Airway Stenosis Being Bypassed by a Customized Tracheostomy Tube in an Infant with Myhre Syndrome

Background: Myhre syndrome is a rare connective tissue disorder caused by heterozygous pathogenic variants in the SMAD4 gene. Although recognizing Myhre syndrome in early childhood is challenging, it is important to manage airway stenosis in patients with Myhre syndrome. Case Presentation: We report the case of a 2-month-old boy who initially presented with severe multilevel airway stenosis, dysmorphic face, and multiple abnormalities. Lung fibrosis and mild aortic valve stenosis were additionally observed on follow-up examinations. A heterozygous missense variant, c.1499T>C (p.Ile500Thr), in SMAD4 was identified through exome sequencing. Tracheostomy was performed, and the patient has maintained stable respiration through a customized tracheostomy tube with a home ventilator. Conclusions: Patients who have dysmorphic face, airway stenosis, and cardiovascular anomalies that do not fit the diagnosis of common syndromes should be evaluated for rare diseases, including Myhre syndrome. Since respiratory complications can be life threatening, early diagnosis and suitable intervention are necessary.

Congenital polyvalvular disease expands the cardiac phenotype of the RASopathies

The RASopathies are a group of similar genetic syndromes with cardiovascular abnormalities, characteristic facial features, short stature, abnormalities of the skin and musculoskeletal system, and variable neurodevelopmental challenges. The most common cardiovascular abnormalities include pulmonary valvular stenosis and hypertrophic cardiomyopathy. Congenital polyvalvular disease (CPVD) refers to congenital dysplasia of two or more cardiac valves. We diagnosed a RASopathy in two individuals with CPVD and noted that CPVD in RASopathies has rarely been reported in the literature. Thus, we performed a retrospective chart review and literature review to investigate the association and characterize the phenotype of CPVD in the RASopathies. CPVD was present in 2.5% (n = 6/243) of individuals in our RASopathy cohort. Involvement of two cardiac valves, commonly the aortic and pulmonic valves, was seen in the majority of individuals (6/8; 75%) in our cohort, but only 27% (3/11) of reported CPVD and RASopathy cases in the literature. CPVD should be considered an associated cardiovascular phenotype of the RASopathies, which has implications for diagnosis and management.

Case Report: Improved Height in a Patient With Myhre Syndrome Using a Combination of Growth Hormone and Letrozole

Myhre syndrome is a rare disorder caused by a heterozygous mutation in the SMAD4 gene. Affected patients may exhibit dysmorphic facial features, intrauterine growth retardation, short stature, obesity, muscle hypertrophy, thickened skin, limited joint movement, hearing impairment, and varying degrees of psychomotor developmental disorder. Serious complications of the cardiovascular and respiratory system may be seen later in life. We report the case of a Chinese boy with Myhre syndrome presenting with a novel symptom of giant testicles where treatment with growth hormone combined with letrozole successfully improved his short stature. This case shows that letrozole combined with growth hormone can improve height in children with Myhre syndrome without adverse effects.

A case of Myhre syndrome mimicking juvenile scleroderma

BACKGROUND

Myhre syndrome is a genetic disorder caused by gain of function mutations in the SMAD Family Member 4 (SMAD4) gene, resulting in progressive, proliferative skin and organ fibrosis. Skin thickening and joint contractures are often the main presenting features of the disease and may be mistaken for juvenile scleroderma.

CASE PRESENTATION

We report a case of a 13 year-old female presenting with widespread skin thickening and joint contractures from infancy. She was diagnosed with diffuse cutaneous systemic sclerosis, and treatment with corticosteroids and subcutaneous methotrexate recommended. There was however disease progression prompting genetic testing. This identified a rare heterozygous pathogenic variant c.1499 T > C (p.Ile500Thr) in the SMAD4 gene, suggesting a diagnosis of Myhre syndrome. Securing a molecular diagnosis in this case allowed the cessation of immunosuppression, thus reducing the burden of unnecessary and potentially harmful treatment, and allowing genetic counselling.

CONCLUSION

Myhre Syndrome is a rare genetic mimic of scleroderma that should be considered alongside several other monogenic diseases presenting with pathological fibrosis from early in life. We highlight this case to provide an overview of these genetic mimics of scleroderma, and highlight the molecular pathways that can lead to pathological fibrosis. This may provide clues to the pathogenesis of sporadic juvenile scleroderma, and could suggest novel therapeutic targets.

The future is here: Integrating genetics into the pediatric pulmonary clinic

Recognition of underlying genetic etiologies of disease is increasing at an exponential rate, likely due to greater access to and lower cost of genetic testing. Monogenic causes of disease, or conditions resulting from a mutation or mutations in a single gene, are now well recognized in every subspecialty, including pediatric pulmonary medicine; thus, it is important to consider genetic conditions when evaluating children with respiratory disease. In the pediatric pulmonary clinic, genetic testing should be considered when multiple family members present with similar or related clinical features and when individuals have unusual clinical presentations, such as early-onset disease or complex, syndromic features. This review provides a practical guide for genetic diagnosis in the pediatric pulmonary setting, including a review of genetic concepts, considerations for test selection and results in interpretation, as well as an overview of genetic differential diagnoses for common pediatric pulmonary phenotypes. Genetic conditions that commonly present to the pediatric pulmonary clinic are reviewed in a companion article by Yonker et al.

Myhre Syndrome Associated With Dunbar Syndrome and Urinary Tract Abnormalities: A Case Report

Myhre syndrome is a rare condition caused by a mutation in the SMAD4 gene, which leads to a defective TGF-β/BMP signaling, resulting in the proliferation of abnormal fibrous tissues. Clinically, patients with Myhre syndrome manifest with defects of connective tissue (skin, muscles, joints), and cardiovascular and neurological impairment. In our report, we present a case of a 16-year-old female with skeletal abnormalities, reduced articular mobility, skin, and muscular hypertrophy and cardiovascular defects characteristic of Myhre syndrome. Long-term pulmonary hypertension and arterial hypertension were persistent in spite of antihypertensive treatment. Our patient was also diagnosed with chronic kidney disease and Dunbar syndrome, which is an external compression of the coeliac trunk or coeliac artery by the surrounding tissues. Until now, only a few cases of renal complications in Myhre syndrome have been published. We describe for the first time a female patient with genetically confirmed Myhre syndrome caused by the p.Ile500Val SMAD4 mutation presenting with an unusual occurrence of congenital vesicoureteral reflux, proteinuria with a decreased renal function, and a condition recognized as Dunbar syndrome.

Gain-of-function pathogenic variants in SMAD4 are associated with neoplasia in Myhre syndrome

Myhre syndrome is an increasingly diagnosed rare syndrome that is caused by one of two specific heterozygous gain-of-function pathogenic variants in SMAD4. The phenotype includes short stature, characteristic facial appearance, hearing loss, laryngotracheal stenosis, arthritis, skeletal abnormalities, learning and social challenges, distinctive cardiovascular defects, and a striking fibroproliferative response in the ear canals, airways, and serosal cavities (peritoneum, pleura, pericardium). Confirmation of the clinical diagnosis is usually prompted by the characteristic appearance with developmental delay and autistic-like behavior using targeted gene sequencing or by whole exome sequencing. We describe six patients (two not previously reported) with molecularly confirmed Myhre syndrome and neoplasia. Loss-of-function pathogenic variants in SMAD4 cause juvenile polyposis syndrome and we hypothesize that the gain-of-function pathogenic variants observed in Myhre syndrome may contribute to neoplasia in the patients reported herein. The frequency of neoplasia (9.8%, 6/61) in this series (two new, four reported patients) and endometrial cancer (8.8%, 3/34, mean age 40 years) in patients with Myhre syndrome, raises the possibility of cancer susceptibility in these patients. We alert clinicians to the possibility of detecting this syndrome when cancer screening panels are used. We propose that patients with Myhre syndrome are more susceptible to neoplasia, encourage increased awareness, and suggest enhanced clinical monitoring.

The first two Chinese Myhre syndrome patients with the recurrent SMAD4 pathogenic variants: Functional consequences and clinical diversity

Myhre syndrome is a rare autosomal dominant multi-organ disorder characterized by growth retardation, skeletal anomalies, muscular hypertrophy, joint stiffness, facial dysmorphism, deafness, cardiovascular disease, and abnormal sexual development. Here we described the first two Chinese Myhre syndrome patients diagnosed by whole-exome sequencing. They both had de novo c.1498A > G (p.Ile500Val) variant in SMAD4 and presented with key characteristics of Myhre syndrome but also revealed uncommon features (polydactyly in the girl and precocious puberty in the boy). We performed functional analysis on four previously reported SMAD4 pathogenic variants in Myhre syndrome patients using dual-luciferase assay. Our results revealed that the pathogenic variants resulted in a variable degree of increased transcription activity of target genes that contain the minimal SMAD binding elements in their promoter regions. The boy responded to the recombinant human growth hormone treatment with improved height but also led to hyperinsulinemia and advanced bone age. Because of his precocious puberty, we subsequently combined the recombinant human growth hormone and gonadotrophin-releasing hormone agonist treatments, which resulted in overall improved height. We reviewed the sexual features of reported Myhre syndrome cases and discussed the possible mechanism of SMAD4 variants in Myhre syndrome that lead to the abnormal hypothalamic-pituitary-gonadal axis.

A child with Myhre syndrome presenting with corectopia and tetralogy of Fallot

Myhre syndrome is a rare autosomal dominant disorder caused by a narrow spectrum of missense mutations in the SMAD4 gene. Typical features of this disorder are distinctive facial appearance, deafness, intellectual disability, cardiovascular abnormalities, short stature, short hands and feet, compact build, joint stiffness, and skeletal anomalies. The clinical features generally appear during childhood and become more evident in older patients. Therefore, the diagnosis of this syndrome in the first years of life is challenging. We report a 2‐year‐old girl diagnosed with Myhre syndrome by whole exome sequencing (WES) that revealed the recurrent p.Ile500Val mutation in the SMAD4 gene. Our patient presented with growth deficiency, dysmorphic features, tetralogy of Fallot, and corectopia (also known as ectopia pupillae). The girl we described is the youngest patient with Myhre syndrome. Moreover, corectopia and tetralogy of Fallot have not been previously reported in this disorder.

Familial clustering of congenital deafness, patent ductus arteriosus, Eisenmenger complex, and differential cyanosis: A case report

RATIONALE

Few studies had reported syndromes that include patent ductus arteriosus (PDA) with Eisenmenger syndrome and congenital deafness clustered in male siblings without facial, skeletal, or mental abnormalities.

PATIENT CONCERNS

Two brothers, who were deaf and had PDA with Eisenmenger complex, were first seen at our Cardiology clinic at the ages of 25 and 41, respectively. They presented with progressive dyspnea on exertion. Upon physical examination, both brothers had clubbing and/or cyanotic toes, normal fingers, and without facial, skeletal, ophthalmological, or mental abnormalities.

DIAGNOSES AND INTERVENTIONS

Echocardiography and multidetector computed tomography revealed large PDAs in both brothers. Cardiac catheterization showed bidirectional shunting via the PDA.

OUTCOMES AND LESSONS

Familial clustering of Eisenmenger PDA and congenital deafness is rare. Further studies are warranted to define possible genetic links.

Natural history and life-threatening complications in Myhre syndrome and review of the literature

Myhre syndrome (OMIM 139210) is a rare developmental disorder inherited as an autosomal dominant trait and caused by a narrow spectrum of missense mutations in the SMAD4 gene. The condition features characteristic face, short stature, skeletal anomalies, muscle pseudohypertrophy, restricted joint mobility, stiff and thick skin, and variable intellectual disability. While most of the clinical features manifest during childhood, the diagnosis may be challenging during the first years of life. We report on the evolution of the clinical features of Myhre syndrome during childhood in a subject with molecularly confirmed diagnosis. The clinical records of 48 affected patients were retrospectively analysed to identify any early clinical signs characterizing this disorder and to better delineate its natural history. We also note that pericarditis and laryngotracheal involvement represent important life-threatening complications of Myhre syndrome that justify the recommendation for cardiological and ENT follow-up for these patients.

CONCLUSION

Short length/stature, short palpebral fissures, and brachydactyly with hyperconvex nails represent signs/features that might lead to the correct diagnosis in the first years of life and direct to the proper molecular analysis. We underline the clinical relevance of pericarditis and laryngotracheal stenosis as life-threatening complications of this disorder and the need for careful monitoring, in relation to their severity.

WHAT IS KNOWN

• The clinical and radiological signs of the disease in children older than 7-8 years. • Pericarditis, sometimes occurring with constrictive pericardium requiring pericardiectomy, has been reported as a recurrent feature but has not been adequately stressed in previous literature. What is New: • Short length/stature, short palpebral fissures, brachydactyly with hyperconvex nails represent clinical signs that might lead to diagnosis in the first years of life. • Review of the literature showed that pericarditis and laryngotracheal complications represent major recurrent issues in patients with Myhre syndrome.

Gain-of-function mutations in SMAD4 cause a distinctive repertoire of cardiovascular phenotypes in patients with Myhre syndrome

Myhre syndrome is a rare, distinctive syndrome due to specific gain-of-function mutations in SMAD4. The characteristic phenotype includes short stature, dysmorphic facial features, hearing loss, laryngotracheal anomalies, arthropathy, radiographic defects, intellectual disability, and a more recently appreciated spectrum of cardiovascular defects with a striking fibroproliferative response to surgical intervention. We report four newly described patients with typical features of Myhre syndrome who had (i) a mildly narrow descending aorta and restrictive cardiomyopathy; (ii) recurrent pericardial and pleural effusions; (iii) a large persistent ductus arteriosus with juxtaductal aortic coarctation; and (iv) restrictive pericardial disease requiring pericardiectomy. Additional information is provided about a fifth previously reported patient with fatal pericardial disease. A literature review of the cardiovascular features of Myhre syndrome was performed on 54 total patients, all with a SMAD4 mutation. Seventy percent had a cardiovascular abnormality including congenital heart defects (63%), pericardial disease (17%), restrictive cardiomyopathy (9%), and systemic hypertension (15%). Pericarditis and restrictive cardiomyopathy are associated with high mortality (three patients each among 10 deaths); one patient with restrictive cardiomyopathy also had epicarditis. Cardiomyopathy and pericardial abnormalities distinguish Myhre syndrome from other disorders caused by mutations in the TGF-β signaling cascade (Marfan, Loeys-Dietz, or Shprintzen-Goldberg syndromes). We hypothesize that the expanded spectrum of cardiovascular abnormalities relates to the ability of the SMAD4 protein to integrate diverse signaling pathways, including canonical TGF-β, BMP, and Activin signaling. The co-occurrence of congenital and acquired phenotypes demonstrates that the gene product of SMAD4 is required for both developmental and postnatal cardiovascular homeostasis. © 2016 Wiley Periodicals, Inc.

Discovery of a potentially deleterious variant in TMEM87B in a patient with a hemizygous 2q13 microdeletion suggests a recessive condition characterized by congenital heart disease and restrictive cardiomyopathy

Restrictive cardiomyopathy (RCM) is a rare cause of heart muscle disease with the highest mortality rate among cardiomyopathy types. The etiology of RCM is poorly understood, although genetic causes have been implicated, and syndromic associations have been described. Here, we describe a patient with an atrial septal defect and restrictive cardiomyopathy along with craniofacial anomalies and intellectual disabilities. Initial screening using chromosomal microarray analysis (CMA) identified a maternally inherited 2q13 microdeletion. The patient had many of the features reported in previous cases with the recurrent 2q13 microdeletion syndrome. However, the inheritance of the microdeletion from an unaffected mother combined with the low incidence (10%) and milder forms of cardiac defects in previously reported cases made the clinical significance of the CMA results unclear. Whole-exome sequencing (WES) with trio-based analysis was performed and identified a paternally inherited TMEM87B mutation (c.1366A>G, p.Asn456Asp) in the patient. TMEM87B, a highly conserved, transmembrane protein of currently unknown function, lies within the critical region of the recurrent 2q13 microdeletion syndrome. Furthermore, a recent study had demonstrated that depletion of TMEM87B in zebrafish embryos affected cardiac development and led to cardiac hypoplasia. Thus, by combining CMA and WES, we potentially uncover an autosomal-recessive disorder characterized by a severe cardiac phenotype caused by mutations in TMEM87B. This study expands the spectrum of phenotypes associated with the recurrent 2q13 microdeletion syndrome and also further suggests the role of TMEM87B in its etiology, especially the cardiac pathology.

BMP signalling in skeletal development, disease and repair

Since the identification in 1988 of bone morphogenetic protein 2 (BMP2) as a potent inducer of bone and cartilage formation, BMP superfamily signalling has become one of the most heavily investigated topics in vertebrate skeletal biology. Whereas a large part of this research has focused on the roles of BMP2, BMP4 and BMP7 in the formation and repair of endochondral bone, a large number of BMP superfamily molecules have now been implicated in almost all aspects of bone, cartilage and joint biology. As modulating BMP signalling is currently a major therapeutic target, our rapidly expanding knowledge of how BMP superfamily signalling affects most tissue types of the skeletal system creates enormous potential to translate basic research findings into successful clinical therapies that improve bone mass or quality, ameliorate diseases of skeletal overgrowth, and repair damage to bone and joints. This Review examines the genetic evidence implicating BMP superfamily signalling in vertebrate bone and joint development, discusses a selection of human skeletal disorders associated with altered BMP signalling and summarizes the status of modulating the BMP pathway as a therapeutic target for skeletal trauma and disease.