THUMPD1 bi-allelic variants cause loss of tRNA acetylation and a syndromic neurodevelopmental disorder.

Covalent tRNA modifications play multi-faceted roles in tRNA stability, folding, and recognition, as well as the rate and fidelity of translation, and other cellular processes such as growth, development, and stress responses. Mutations in genes that are known to regulate tRNA modifications lead to a wide array of phenotypes and diseases including numerous cognitive and neurodevelopmental disorders, highlighting the critical role of tRNA modification in human disease. One such gene, THUMPD1, is involved in regulating tRNA N4-acetylcytidine modification (ac4C), and recently was proposed as a candidate gene for autosomal-recessive intellectual disability. Here, we present 13 individuals from 8 families who harbor rare loss-of-function variants in THUMPD1. Common phenotypic findings included global developmental delay, speech delay, moderate to severe intellectual deficiency, behavioral abnormalities such as angry outbursts, facial dysmorphism, and ophthalmological abnormalities. We demonstrate that the bi-allelic variants identified cause loss of function of THUMPD1 and that this defect results in a loss of ac4C modification in small RNAs, and of individually purified tRNA-Ser-CGA. We further corroborate this effect by showing a loss of tRNA acetylation in two CRISPR-Cas9-generated THUMPD1 KO cell lines. In addition, we also show the resultant amino acid substitution that occurs in a missense THUMPD1 allele identified in an individual with compound heterozygous variants results in a marked decrease in THUMPD1 stability and RNA-binding capacity. Taken together, these results suggest that the lack of tRNA acetylation due to THUMPD1 loss of function results in a syndromic form of intellectual disability associated with developmental delay, behavioral abnormalities, hearing loss, and facial dysmorphism.

SDHA mutations in adult and pediatric wild-type gastrointestinal stromal tumors.

Most gastrointestinal stromal tumors (GISTs) harbor oncogenic mutations in KIT or platelet-derived growth factor receptor-α. However, a small subset of GISTs lacks such mutations and is termed 'wild-type GISTs'. Germline mutation in any of the subunits of succinate dehydrogenase (SDH) predisposes individuals to hereditary paragangliomas and pheochromocytomas. However, germline mutations of the genes encoding SDH subunits A, B, C or D (SDHA, SDHB, SDHC or SDHD; collectively SDHx) are also identified in GISTs. SDHA and SDHB immunohistochemistry are reliable techniques to identify pheochromocytomas and paragangliomas with mutations in SDHA, SDHB, SDHC and SDHD. In this study, we investigated if SDHA immunohistochemistry could also identify SDHA-mutated GISTs. Twenty-four adult wild-type GISTs and nine pediatric/adolescent wild-type GISTs were analyzed with SDHB, and where this was negative, then with SDHA immunohistochemistry. If SDHA immunohistochemistry was negative, sequencing analysis of the entire SDHA coding sequence was performed. All nine pediatric/adolescent GISTs and seven adult wild-type GISTs were negative for SDHB immunohistochemistry. One pediatric GIST and three SDHB-immunonegative adult wild-type GISTs were negative for SDHA immunohistochemistry. In all four SDHA-negative GISTs, a germline SDHA c.91C>T transition was found leading to a nonsense p.Arg31X mutation. Our results demonstrate that SDHA immunohistochemistry on GISTs can identify the presence of an SDHA germline mutation. Identifying GISTs with deficient SDH activity warrants additional genetic testing, evaluation and follow-up for inherited disorders and paragangliomas.

Acute pulmonary vasodilator response in paediatric and adult pulmonary arterial hypertension: occurrence and prognostic value when comparing three response criteria.

AIMS: To assess the occurrence and prognostic value of acute vasodilator response (AVR) in paediatric vs. adult pulmonary arterial hypertension, and idiopathic/hereditary pulmonary arterial hypertension (iPAH/HPAH) vs. pulmonary arterial hypertension associated with congenital heart disease (PAH-CHD) using three different response criteria. METHODS AND RESULTS: Ninety-nine PAH patients underwent AVR testing (37 children, 62 adults; 70 iPAH/HPAH, 29 PAH-CHD). Three response criteria from clinical practice were used to define AVR. The number of responders was evaluated separately in subgroups based on age, diagnosis, and presence of a non-restrictive post-tricuspid shunt. Numbers of responders varied importantly using the different criteria but were always higher in iPAH/HPAH, compared with PAH-CHD. The number of responders did not differ between paediatric and adult iPAH/HPAH. No responders were identified in patients with a post-tricuspid shunt. Acute vasodilator response was associated with improved survival using all three criteria. Low baseline mean right atrial pressure (mRAP) was associated with improved survival in adults (P< 0.001). High baseline mean pulmonary arterial pressure (mPAP)/mean systemic arterial pressure (mSAP) and pulmonary vascular resistance (PVR)/systemic vascular resistance (SVR) were associated with worse survival, statistically independent from age, diagnosis, and the presence of a post-tricuspid shunt. CONCLUSION: The proportion of patients with AVR highly depends on the used criteria, but did not differ between paediatric and adult iPAH/HPAH. Current response criteria are not suitable for patients with a post-tricuspid shunt. In both children and adults without post-tricuspid shunts, AVR was associated with improved survival independent of the used criteria. Nevertheless, prognostic value in the individual patient was limited. Baseline mRAP showed a good correlation with survival for adult PAH patients, but not for children. High baseline mPAP/mSAP and PVR/SVR was associated with worse prognosis independent from age, diagnosis, or the presence of a post-tricuspid shunt.

The etiology of cardiac hypertrophy in infants.

This study aimed to describe the variety of etiologies currently identified in infants with cardiac hypertrophy (CH) and investigate whether there is a relation with hyperinsulinism, echocardiographic characteristics and prognosis. This retrospective cohort study included infants born between 2005 and 2018 with CH measured by echocardiography [interventricular septum (IVS) and/or left ventricular posterior wall (LVPW) thickness with Z-score ≥ 2.0]. Children with congenital heart disease or hypertension were excluded. Underlying diagnosis, echocardiographic and follow-up data were extracted from patient files. Seventy-one infants with CH were included. An underlying cause of CH was identified in two-thirds (n = 47). Most common etiologies of CH were malformation syndromes (n = 23, including Noonan n = 12) and maternal diabetes mellitus (n = 13). Less common causes were congenital hyperinsulinism (n = 3), metabolic- (n = 5), sarcomeric- (n = 2) and neuromuscular disease (n = 1). In half of the identified causes (n = 22) an association with hyperinsulinism was described, including maternal diabetes mellitus (n = 13), malformation syndromes with insulin resistance (n = 6) and congenital hyperinsulinism (n = 3). CH associated with hyperinsulinism was echocardiographically characterized by lower LVPW thickness, higher IVS:LVPW ratio and more frequent sole involvement of the IVS (all, p ≤ 0.02). CH associated with hyperinsulinism normalized more often (41 vs. 0%) with lower mortality rates (14 vs. 44%) compared to CH not associated with hyperinsulinism (all, p ≤ 0.03). Nowadays, an etiology of CH can be identified in the majority of infants. The development of CH is often associated with hyperinsulinism which is mainly characterized by focal hypertrophy of the IVS on echocardiography. Prognosis depends on the underlying cause and is more favorable in CH associated with hyperinsulinism.

Prevalence and clinical outcomes of dystrophin-associated dilated cardiomyopathy without severe skeletal myopathy.

AIMS: Dilated cardiomyopathy (DCM) associated with dystrophin gene (DMD) mutations in individuals with mild or absent skeletal myopathy is often indistinguishable from other DCM forms. We sought to describe the phenotype and prognosis of DMD associated DCM in DMD mutation carriers without severe skeletal myopathy. METHODS AND RESULTS: At 26 European centres, we retrospectively collected clinical characteristics and outcomes of 223 DMD mutation carriers (83% male, 33 ± 15 years). A total of 112 individuals (52%) had DCM at first evaluation [n = 85; left ventricular ejection fraction (LVEF) 34 ± 11.2%] or developed DCM (n = 27; LVEF 41.3 ± 7.5%) after a median follow-up of 96 months (interquartile range 5-311 months). DCM penetrance was 45% in carriers older than 40 years. DCM appeared earlier in males and was independent of the type of mutation, presence of skeletal myopathy, or elevated serum creatine kinase levels. Major adverse cardiac events (MACE) occurred in 22% individuals with DCM, 18% developed end-stage heart failure and 9% sudden cardiac death or equivalent. Skeletal myopathy was not associated with survival free of MACE in patients with DCM. Decreased LVEF and increased left ventricular end-diastolic diameter at baseline were associated with MACE. Individuals without DCM had favourable prognosis without MACE or death during follow-up. CONCLUSIONS: DMD-associated DCM without severe skeletal myopathy is characterized by incomplete penetrance but high risk of MACE, including progression to end-stage heart failure and ventricular arrhythmias. DCM onset is the major determinant of prognosis with similar survival regardless of the presence of skeletal myopathy.

Three female patients with Danon disease presenting with predominant cardiac phenotype: a case series.

BACKGROUND: Danon disease is a rare X-linked multisystemic disorder that has primarily been described in male patients. CASE SUMMARY: We present three female patients with Danon disease with a predominantly cardiac phenotype in whom disease onset and expression was very different from that of male patients. Case 1 was first admitted for acute heart failure and then readmitted a few months later for cardiac shock, necessitating mechanical support, and heart transplantation. Case 2 had complex arrhythmias for which many antiarrhythmic drugs were tried with only limited success. Her disease accelerated after her first pregnancy, and she showed reduced left ventricular function and dilated cardiomyopathy. Case 3 was referred for near syncope and ablated for an accessory pathway; she had extensive left ventricular hypertrophy. In all three cases, a final diagnosis of Danon disease was only made after genetic testing that identified a causal variant in the lysosome-associated membrane protein 2 gene. DISCUSSION: Danon disease in female patients is a challenging diagnosis that may not be identified until genetic testing has been performed.

Further delineation of the KBG syndrome phenotype caused by ANKRD11 aberrations.

Loss-of-function variants in ANKRD11 were identified as the cause of KBG syndrome, an autosomal dominant syndrome with specific dental, neurobehavioural, craniofacial and skeletal anomalies. We present the largest cohort of KBG syndrome cases confirmed by ANKRD11 variants reported so far, consisting of 20 patients from 13 families. Sixteen patients were molecularly diagnosed by Sanger sequencing of ANKRD11, one familial case and three sporadic patients were diagnosed through whole-exome sequencing and one patient was identified through genomewide array analysis. All patients were evaluated by a clinical geneticist. Detailed orofacial phenotyping, including orthodontic evaluation, intra-oral photographs and orthopantomograms, was performed in 10 patients and revealed besides the hallmark feature of macrodontia of central upper incisors, several additional dental anomalies as oligodontia, talon cusps and macrodontia of other teeth. Three-dimensional (3D) stereophotogrammetry was performed in 14 patients and 3D analysis of patients compared with controls showed consistent facial dysmorphisms comprising a bulbous nasal tip, upturned nose with a broad base and a round or triangular face. Many patients exhibited neurobehavioural problems, such as autism spectrum disorder or hyperactivity. One-third of patients presented with (conductive) hearing loss. Congenital heart defects, velopharyngeal insufficiency and hip anomalies were less frequent. On the basis of our observations, we recommend cardiac assessment in children and regular hearing tests in all individuals with a molecular diagnosis of KBG syndrome. As ANKRD11 is a relatively common gene in which sequence variants have been identified in individuals with neurodevelopmental disorders, it seems an important contributor to the aetiology of both sporadic and familial cases.

Sildenafil add-on therapy in paediatric pulmonary arterial hypertension, experiences of a national referral centre.

OBJECTIVE: In paediatric pulmonary arterial hypertension (PAH), the effectiveness of add-on combination PAH-therapy has not yet been systematically studied. The purpose of this study was to determine the effect of sildenafil add-on therapy in paediatric PAH patients treated with bosentan. METHODS: In this observational study within a national paediatric patient cohort, follow-up data of 24 consecutive paediatric PAH patients initially treated with bosentan monotherapy and prospectively followed at the Dutch national referral centre for paediatric PAH in 2007-2013, were reviewed. Patients received add-on sildenafil therapy in case of clinical worsening. RESULTS: Fifteen children received add-on sildenafil therapy; nine remained on bosentan monotherapy. Patient characteristics, 6-minute walk distance (6MWD), WHO functional class (WHO-FC), N-terminal pro-Brain Natriuretic Peptide (NT-proBNP), and haemodynamic measurements at bosentan start were similar in both patient groups. In children with clinical worsening, sildenafil add-on therapy improved 6MWD at 5, 10, 15 and 21 months of follow-up, improved WHO-FC at 10, 15 and 21 months and stabilised NT-proBNP. Patients who received add-on sildenafil therapy had more advanced disease progression during bosentan monotherapy. Despite that, they had better or, at least, no worse survival compared to patients who remained on bosentan monotherapy. CONCLUSIONS: In children with PAH, sildenafil add-on therapy indicated by clinical deterioration on bosentan monotherapy, was associated with a significant improvement of WHO-functional class and 6MWD. Despite clinical deterioration on bosentan monotherapy, patients receiving sildenafil add-on therapy, had either better or, at least, no worse survival than patients remaining on bosentan monotherapy.

[Pulmonary arterial hypertension in childhood]. / Pulmonale arteriële hypertensie bij kinderen in Nederland.

Progressive pulmonary arterial hypertension (PAH) is a rare condition with high morbidity and mortality. Paediatric PAH distinguishes itself from PAH in adults, but is still poorly characterized. Paediatric PAH presents itself with non-specific symptoms which often results in later diagnosis. Determination of the correct underlying diagnosis in paediatric PAH is complex, and must therefore take place at specialized centres. Paediatric progressive PAH is usually either idiopathic or associated with congenital heart disease. Pediatric PAH frequently co-occurs with dysmorphic abnormalities, which may point towards aetiological mechanisms. Recent reports suggest an improved survival and exercise tolerance due to treatment with new second-generation drugs for paediatric PAH. In the Netherlands, the care for children with PAH is centralised to guarantee the optimization of diagnosis and treatment in accordance with the most recent scientific insights.

Down patients with Eisenmenger syndrome: is bosentan treatment an option?

BACKGROUND: Favorable results of treatment with bosentan in patients with Eisenmenger syndrome are available. However, data in Down patients are lacking. In this study, we evaluate the therapeutic role of bosentan treatment in Down patients with Eisenmenger syndrome. METHODS: In this open-label study, 24 Down patients (>18 years) with Eisenmenger syndrome (17 males) were treated with bosentan. Their mean age was 38 years (range 19-55 years). All Down patients were evaluated at baseline and during follow-up with laboratory tests, six-minute walk test (6-MWT), Doppler echocardiography, and quality of life questionnaires. RESULTS: The median follow-up of Down patients treated with bosentan was 11.5 months (range 3-23 months). Induction of oral bosentan therapy was well tolerated among all 24 Down patients. Bosentan treatment was generally well tolerated. No serious adverse drug reactions were noted. Median 6-MWT increased from 296 m (range 40-424 m) to 325 m (range 84-459 m, p<0.05) after 12 weeks. After 26 and 52 weeks of treatment with bosentan, median 6-MWT distance was 276 m (range 140-462 m, n=15, p=0.6) and 287 m (range 131-409 m, n=7, p=0.3), respectively. Quality of life questionnaire scores remained stable during treatment. CONCLUSION: Also patients with Down syndrome may benefit from bosentan treatment when they have Eisenmenger syndrome. Medical treatment appears to be safe and the treatment effects do not deviate from those observed in Eisenmenger patients without Down syndrome.

Effect of bosentan on exercise capacity and quality of life in adults with pulmonary arterial hypertension associated with congenital heart disease with and without Down's syndrome.

Pulmonary arterial hypertension associated with congenital heart disease caused by systemic-to-pulmonary shunting was associated with a high risk of morbidity and mortality. In this retrospective study, the longer term treatment effect of bosentan on exercise capacity and quality of life (QoL) were evaluated in 58 adult patients (>18 years) with pulmonary arterial hypertension associated with congenital heart disease, including patients with Down's syndrome. All patients were evaluated at baseline and during follow-up using laboratory tests, 6-minute walk test, QoL questionnaires, and Doppler echocardiography. Treatment efficacy was analyzed separately for patients without (n = 30) and with Down's syndrome (n = 28). Median follow-up of all patients treated with bosentan was 22 months (range 3 to 36). In patients without Down's syndrome, mean 6-minute walk distance increased from 427 +/- 97 to 461 +/- 104 m (p <0.01) after 6 months of treatment, followed by a gradual return to baseline and disease stabilization. QoL improved significantly during treatment and was maintained during 18 months of follow-up (p <0.05). In patients with Down's syndrome, 6-minute walk distance and QoL were stable during treatment. In conclusion, findings suggested that in patients without Down's syndrome, longer term bosentan treatment resulted in a persistent improvement in QoL and stabilization of exercise capacity.