Coexistence of pulmonary arterial hypertension and straight back syndrome in a patient with a novel BMPR2 variant affecting cytoplasmic tail domain

BACKGROUND

Pathologic variants in the bone morphogenetic protein receptor-2 (BMPR2) gene cause a pulmonary arterial hypertension phenotype in an autosomal-dominant pattern with incomplete penetrance. Straight back syndrome is one of the causes of pseudo-heart diseases. To date, no cases of idiopathic or heritable pulmonary arterial hypertension with straight back syndrome have been reported.

CASE PRESENTATION

A 30-year-old female was diagnosed with pulmonary arterial hypertension by right heart catheterization. Computed tomography revealed a decreased anteroposterior thoracic space with heart compression, indicating a straight back syndrome. Genetic analysis by whole exome sequencing identified a novel c.2423_2424delGT (p.G808Gfs*4) germline frameshift variant within BMPR2 affecting the cytoplasmic tail domain.

CONCLUSIONS

This is the first report of different straight back characteristics in heritable pulmonary arterial hypertension with a novel germline BMPR2 variant. This finding may provide a new perspective on the variable penetrance of the pulmonary arterial hypertension phenotype.

Related mechanisms and research progress in straight back syndrome

Despite the high prevalence of straight back syndrome (SBS), there is still limited research on this condition, posing challenges for effective diagnosis and treatment. The disease has been known for a long time, but there have been few related studies, which mostly consist of case reports. These studies have not been systematically summarized, making it difficult to meet the current needs of diagnosis and treatment. This article summarized the existing literature and comprehensively reviewed the diagnosis, pathogenesis, treatment, and research status of mitral valve prolapse related to SBS. We specifically emphasized the mechanisms and prognosis of SBS combined with mitral valve prolapse and discussed the latest research progress in this disease.

A mechanism of a cardiac murmur with respiratory variation in a patient with straight back syndrome

A 20-year-old male without any symptoms was referred for heart murmur on a medical examination. A thrill was palpable at the upper left sternal border. His cardiac murmur showed respiratory variation. The systolic murmur was louder (Levine grade IV/VI) during expiration and diminished during inspiration (Levine grade I/VI). He was thin and had a narrow thoracic cage in the anteroposterior direction due to straight back syndrome (SBS). An echocardiogram and a right ventriculogram showed changes in the diameter of the right ventricular outflow tract (RVOT) on respiration. During expiration, the RVOT was compressed and narrow, while it was expanded during inspiration. Cardiac catheterization demonstrated a 10-mmHg of pressure gradient across the RVOT during expiration but no pressure gradient during inspiration. Thus, respiratory compression to the RVOT by a narrow thoracic cage due to SBS was the cause of the cardiac murmur with respiratory alterations. Our case highlights the importance of physical examination, including an inspection of the patient's physique. <Learning objective: When examining a patient with a cardiac murmur, respiratory alterations of cardiac murmurs should be auscultated. In these cases, straight back syndrome would be one of the differential diagnoses and should be considered. During a physical examination, inspection of the patient's physique is also important.>.

Relief of exertional dyspnea and spinal pains by increasing the thoracic kyphosis in straight back syndrome (thoracic hypo-kyphosis) using CBP® methods: a case report with long-term follow-up

[Purpose] To present the clinically significant improvement of straight back syndrome (SBS) in a patient with spinal pain and exertional dyspnea. [Subject and Methods] A 19 year old presented with excessive thoracic hypokyphosis and other postural deviations. A multimodal CBP^® mirror image^® protocol of corrective exercises, traction procedures and spine/posture adjusting were given over an initial 12-week course of intensive treatment followed by a 2.75 year follow-up with minimal supportive treatment. [Results] The patient had significant postural improvements in all postural measures and specifically a 14° increase in the thoracic kyphosis that was maintained at long-term follow-up. The postural improvements were consistent with relief of exertional dyspnea and pain, as well as increases in both antero-posterior thoracic diameter and the ratio of antero-posterior to transthoracic diameter, measurements critical to the wellbeing of patients with SBS. [Conclusion] Long-term follow-up confirmed stable improvement in physiologic thoracic kyphosis in this patient. Nonsurgical correction in thoracic hypokyphosis/SBS can be achieved by mirror image traction procedures configured to flex the thoracic spine into hyperkyphosis as well as corrective exercise and manipulation as a part of CBP technique protocols.

[A preliminary study on the relationship between idiopathic arrhythmia and cardiac magnetic resonance imaging defined cardiac features in patients with straight back syndrome]

Objective: To retrospectively analyze the potential correlation between cardiac magnetic resonance (CMR) imaging and clinical features and idiopathic arrhythmia in patients with straight back syndrome (SBS). Methods: Patients receiving CMR imaging examination from April 2015 to March 2016 at our department (n=1 432) were screened, 76 patients met the diagnosis criteria of flat chest (anteroposterior diameter/transthoracic diameter (APD/TTD) ratio<0.37 at the T8 vertebra). After excluding 33 patients with structural heart disease, 43 SBS patients were divided into two groups: SBS without obvious morphological change in the heart (group A, n=19) and SBS with morphological change of the heart (group B, n=24). CMR images were analyzed, focusing the heart morphological changes induced by SBS. The clinical data were collected to comprehensively analyze the medical history, electrocardiogram and electrophysiological examination in order to observe the relationship between SBS induced heart morphological change and the arrhythmia type and origin. Results: There were 21 male patients in this cohort, mean age was (28.5±11.5) years (13-58 years). APD/TTD ratio was similar between the two groups (0.30±0.03 vs. 0.29±0.04, P>0.05). LVEF tended to be lower in group B than in group A ((47.48±12.77)%vs. (59.31±9.04)%, P>0.05) . In group B, there were 15 patients with left ventricular enlargement, 2 with left ventricular wall thickening, 5 with uncoordinated ventricular wall motion, 5 with tricuspid regurgitation, 3 with mitral regurgitation, 2 with myocardial fibrosis, 5 with increased trabecular and 16 with decreased left ventricular function. Direct compression sign of right ventricle (disappeared precordial fat tissue space, secondary right atria enlargement and tricuspid regurgitation) and left atria (with or without secondary left ventricular enlargement and mitral regurgitation) were evidenced in patients of group B. CMR revealed that the arrhythmia origin corresponded the compression site of the heart in 8 cases (42.1%) in group A and 13 cases (54.2%) in group B, not corresponded to the compression site in 6 patients (31.6%) in group A and in 7 patients (29.2%) in group B, not attributable in 5 patients (26.3%) in group A and 4 patients (16.7%) in group B. The percent of arrhythmia origin corresponded the compression site of the heart tended to be higher in group B as compared to group A (P>0.05). Conclusion: SBS can induce changes of cardiac morphology and cardiac function. SBS induced cardiac compression is linked with the development of arrhythmias and might be one of the reasons of arrhythmias in these patients.

Nonsurgical correction of straight back syndrome (thoracic hypokyphosis), increased lung capacity and resolution of exertional dyspnea by thoracic hyperkyphosis mirror image® traction: a CBP® case report

[Purpose] To present the increase in thoracic kyphosis in a patient suffering from exertional dyspnea, reduced lung capacity, and spinal pains related to straight back syndrome (SBS). [Subject and Methods] A 33-year-old male patient was put on a CBP^® corrective care program involving mirror image^® traction procedures designed to increase the thoracic kyphosis. [Results] This patient had a 10° improvement in thoracic kyphosis in 16-weeks that was maintained 7-months later. There was a simultaneous reduction of pain, resolved exertional dyspnea, and a greater than 2 liter increase in lung capacity. [Conclusion] This case illustrates that nonsurgical improvement in thoracic kyphosis in a patient with SBS is possible and that this may positively influence lung capacity, health and function.

Straight Back Syndrome

Straight back syndrome is a rare condition usually associated with mitral valve prolapse and "pseudo-heart disease" caused by a very narrow anterior-posterior chest due to the loss of the normal dorsal curvature of the thoracic spine. More rarely, the narrowed upper chest may compress the trachea causing extrinsic tracheal obstruction. If severe enough, this requires operative repair by effectively opening up the upper chest by a variety of techniques to allow the trachea enough room to avoid compression.