Olfactory bulb anomalies in KBG syndrome mouse model and patients.

ANKRD11 (ankyrin repeat domain 11) is a chromatin regulator and the only gene associated with KBG syndrome, a rare neurodevelopmental disorder. We have previously shown that Ankrd11 regulates murine embryonic cortical neurogenesis. Here, we show a novel olfactory bulb phenotype in a KBG syndrome mouse model and two diagnosed patients. Conditional knockout of Ankrd11 in murine embryonic neural stem cells leads to aberrant postnatal olfactory bulb development and reduced size due to reduction of the olfactory bulb granule cell layer. We further show that the rostral migratory stream has incomplete migration of neuroblasts, reduced cell proliferation as well as aberrant differentiation of neurons. This leads to reduced neuroblasts and neurons in the olfactory bulb granule cell layer. In vitro, Ankrd11-deficient neural stem cells from the postnatal subventricular zone display reduced migration, proliferation, and neurogenesis. Finally, we describe two clinically and molecularly confirmed KBG syndrome patients with anosmia and olfactory bulb and groove hypo-dysgenesis/agenesis. Our report provides evidence that Ankrd11 is a novel regulator of olfactory bulb development and neuroblast migration. Moreover, our study highlights a novel clinical sign of KBG syndrome linked to ANKRD11 perturbations in mice and humans.

Usmani-Riazuddin syndrome can have a recognizable phenotype: Report of a novel AP1G1 variant.

Usmani-Riazuddin syndrome (USRISR, MIM# 619548; USRISD, MIM#619467) is a very rare genetic condition. recently associated with deleterious variants in AP1G1 (MIM* 603533). It is characterized by multisystemic involvement including intellectual disability, speech and developmental delay, behavioral anomalies, muscular tone disorders, seizures, limb defects, and unspecified facial gestalt. In this report, we describe this syndrome for the second time, in association to a novel AP1G1 variant identified in a toddler with multisystemic involvement including intellectual disability, speech and developmental delay, behavioral anomalies, arrhythmias, hearing loss, skin changes, and limb defects. Next generation sequencing (NGS) analysis through clinical exome disclosed AP1G1: c.1969C>G (p.Leu657Val), de novo, likely pathogenic variant, according to ACMG classification criteria. Proband's facial features resembled the spectrum of chromatinopathies. Clinical pictures were analyzed and a clinical overlap was supported by DeepGestalt analysis (www.face2gene.com). The system identified 6 chromatin disorders out of 30 possible diagnoses. The remaining 24 included 9 miscellaneous cryptic chromosomal abnormalities (excluded due to normal microarray study). To the best of our knowledge, this is the first description of likely distinctive facial features in a patient with Usmani-Riazuddin syndrome. Further multicentric analyses are needed for a better definition of this aspect.

Deep phenotyping of the neuroimaging and skeletal features in KBG syndrome: a study of 53 patients and review of the literature.

BACKGROUND: KBG syndrome is caused by haploinsufficiency of ANKRD11 and is characterised by macrodontia of upper central incisors, distinctive facial features, short stature, skeletal anomalies, developmental delay, brain malformations and seizures. The central nervous system (CNS) and skeletal features remain poorly defined. METHODS: CNS and/or skeletal imaging were collected from molecularly confirmed individuals with KBG syndrome through an international network. We evaluated the original imaging and compared our results with data in the literature. RESULTS: We identified 53 individuals, 44 with CNS and 40 with skeletal imaging. Common CNS findings included incomplete hippocampal inversion and posterior fossa malformations; these were significantly more common than previously reported (63.4% and 65.9% vs 1.1% and 24.7%, respectively). Additional features included patulous internal auditory canal, never described before in KBG syndrome, and the recurrence of ventriculomegaly, encephalic cysts, empty sella and low-lying conus medullaris. We found no correlation between these structural anomalies and epilepsy or intellectual disability. Prevalent skeletal findings comprised abnormalities of the spine including scoliosis, coccygeal anomalies and cervical ribs. Hand X-rays revealed frequent abnormalities of carpal bone morphology and maturation, including a greater delay in ossification compared with metacarpal/phalanx bones. CONCLUSION: This cohort enabled us to describe the prevalence of very heterogeneous neuroradiological and skeletal anomalies in KBG syndrome. Knowledge of the spectrum of such anomalies will aid diagnostic accuracy, improve patient care and provide a reference for future research on the effects of ANKRD11 variants in skeletal and brain development.

Epilepsy in KBG syndrome.

AIM: To illustrate the epileptological and electroencephalographic (EEG) characteristics of a cohort of patients with KBG syndrome and epilepsy. METHOD: Clinical history, age at epilepsy onset, seizure types, EEG findings, duration of epilepsy, and response to therapies were retrospectively reviewed in 11 patients (three females, eight males) with KBG syndrome. RESULTS: All detected genetic mutations were pathogenic and affected the C-terminal region at exon 9 of ANKRD11. One patient had 16q24.3 microdeletion including the ANKRD11 gene. Mean age at onset was 67 months. Epilepsy type was focal in five patients and generalized in four. Two patients had developmental and epileptic encephalopathies. Seizure freedom was obtained after a period varying between 15 days and 6 years. INTERPRETATION: In our patients, epilepsy appeared to respond well to treatment and, in some cases, to be self-limiting. The molecular characteristics of our patients' genetic abnormalities did not point towards any specific epilepsy hot spot. Epilepsy should be considered in the diagnostic work-up of patients with KBG syndrome. WHAT THIS PAPER ADDS: Some of the epilepsy types of KBG syndrome appear to be self-remitting. The epilepsy phenotypes associated with KBG syndrome are quite variable.

Autosomal Recessive Long QT Syndrome: Clinical Aspects and Therapy.

The autosomal recessive (AR) form of Long QT Syndrome (LQTS) is described both associated with deafness known as Jervell and Lange-Nielsen (JLN) syndrome, and without deafness (WD). The aim of the study is to report the characteristics of AR LQTS patients and the efficacy of the therapy. Data of all children with AR LQTS referred to the Bambino Gesù Children's Hospital IRCCS from September 2012 to September 2021were included. Three (30%) patients had compound heterozygosity and 7 (70%) had homozygous variants of the KCNQ1 gene, the latter showing deafness. Four patients (40%) presented aborted sudden cardiac death (aSCD): three with previous episodes of syncope (75%), the other without previous symptoms (16.6% of asymptomatic patients). An episode of aSCD occurred in 2/3 (66.7%) of WD and heterozygous patients, while in 2/7 (28%) JLN and homozygous patients and in 2/2 patients with QTC > 600 ms. All patients were treated with Nadolol. In 5 Mexiletine was added, shortening QTc and obtaining the disappearance of the T-wave alternance (TWA) in 3/3. Episodes of aSCD seem to be more frequent in LQTS patients with compound heterozygous variants and WD than in those with JLN and homozygous variants. Episodes of aSCD also appear more frequent in children with syncope or with QTc value > 600 ms, even on beta-blocker therapy, than in patients without syncope or with Qtc < 600 ms. However, our descriptive results should be confirmed by larger studies. Moreover, Mexiletine addition reduced QTc value and eliminated TWA.

Congenital heart defects in molecularly confirmed KBG syndrome patients.

Congenital heart defects (CHDs) are known to occur in 9%-25% of patients with KBG syndrome. In this study we analyzed the prevalence and anatomic types of CHDs in 46 personal patients with KBG syndrome, carrying pathogenetic variants in ANKRD11 or 16q24.3 deletion, and reviewed CHDs in patients with molecular diagnosis of KBG syndrome from the literature. CHD was diagnosed in 15/40 (38%) patients with ANKRD11 variant, and in one patient with 16q24.3 deletion. Left ventricular outflow tract obstructions have been diagnosed in 9/15 (60%), subaortic or muscular ventricular septal defect in 5/15 (33%), dextrocardia in 1/15 (8%). The single patient with 16q24.3 deletion and CHD had complete atrioventricular septal defect (AVSD) with aortic coarctation. Review of KBG patients from the literature and present series showed that septal defects have been diagnosed in 44% (27/61) of the cases, left ventricular tract obstructions in 31% (19/61), AVSD in 18% (11/61). Septal defects have been diagnosed in 78% of total patients with 16q24.3 deletion. Valvar anomalies are frequently diagnosed, prevalently involving the left side of the heart. A distinctive association with AVSD is identifiable and could represent a marker to suggest the diagnosis in younger patients. In conclusion, after precise molecular diagnosis and systematic cardiological screening the prevalence of CHD in KBG syndrome seems to be higher than previously reported in clinical articles. In addition to septal defects, left-sided anomalies and AVSD should be considered. Clinical management of KBG syndrome should include accurate and detailed echocardiogram at time of diagnosis.

Clinical delineation, sex differences, and genotype-phenotype correlation in pathogenic KDM6A variants causing X-linked Kabuki syndrome type 2.

PURPOSE: The variant spectrum and the phenotype of X-linked Kabuki syndrome type 2 (KS2) are poorly understood. METHODS: Genetic and clinical details of new and published individuals with pathogenic KDM6A variants were compiled and analyzed. RESULTS: Sixty-one distinct pathogenic KDM6A variants (50 truncating, 11 missense) from 80 patients (34 males, 46 females) were identified. Missense variants clustered in the TRP 2, 3, 7 and Jmj-C domains. Truncating variants were significantly more likely to be de novo. Thirteen individuals had maternally inherited variants and one had a paternally inherited variant. Neonatal feeding difficulties, hypoglycemia, postnatal growth retardation, poor weight gain, motor delay, intellectual disability (ID), microcephaly, congenital heart anomalies, palate defects, renal malformations, strabismus, hearing loss, recurrent infections, hyperinsulinism, seizures, joint hypermobility, and gastroesophageal reflux were frequent clinical findings. Facial features of over a third of patients were not typical for KS. Males were significantly more likely to be born prematurely, have shorter stature, and severe developmental delay/ID. CONCLUSION: We expand the KDM6A variant spectrum and delineate the KS2 phenotype. We demonstrate that the variability of the KS2 phenotypic depends on sex and the variant type. We also highlight the overlaps and differences between the phenotypes of KS2 and KS1.

Idiopathic Ventricular Fibrillation: Look for the Hidden Guilty-A case of aborted cardiac death.

We report a unique case of a 6-year-old male child with aborted sudden cardiac death due to ventricular fibrillation. A rare anomalous aortic origin of the right coronary artery was detected and supposed to be the cause of the malignant arrhythmia. Clinical exome sequencing did not reveal any pathogenic variant related to channelopathies nor other known heart-related genes. The patient underwent cardiac surgery and a cardiac defibrillator was implanted for secondary prevention.

KBG syndrome: Common and uncommon clinical features based on 31 new patients.

KBG syndrome (MIM #148050) is an autosomal dominant disorder characterized by developmental delay, intellectual disability, distinct craniofacial anomalies, macrodontia of permanent upper central incisors, skeletal abnormalities, and short stature. This study describes clinical features of 28 patients, confirmed by molecular testing of ANKRD11 gene, and three patients with 16q24 deletion encompassing ANKRD11 gene, diagnosed in a single center. Common clinical features are reported, together with uncommon findings, clinical expression in the first years of age, distinctive associations, and familial recurrences. Unusual manifestations emerging from present series include juvenile idiopathic arthritis, dysfunctional dysphonia, multiple dental agenesis, idiopathic precocious telarche, oral frenula, motor tics, and lipoma of corpus callosum, pilomatrixoma, and endothelial corneal polymorphic dystrophy. Facial clinical markers suggesting KBG syndrome before 6 years of age include ocular and mouth conformation, wide eyebrows, synophrys, long black eyelashes, long philtrum, thin upper lip. General clinical symptoms leading to early genetic evaluation include developmental delay, congenital malformations, hearing anomalies, and feeding difficulties. It is likely that atypical clinical presentation and overlapping features in patients with multiple variants are responsible for underdiagnosis in KBG syndrome. Improved knowledge of common and atypical features of this disorder improves clinical management.

Burkitt lymphoma in a patient with Kabuki syndrome carrying a novel KMT2D mutation.

Kabuki syndrome (KS) is an extremely rare genetic disorder, mainly caused by germline mutations at specific epigenetic modifier genes, including KMT2D. Because the tumor suppressor gene KMT2D is also frequently altered in many cancer types, it has been suggested that KS may predispose to the development of cancer. However, KS being a rare disorder, few data are available on the incidence of cancer in KS patients. Here, we report the case of a 5-year-old boy affected by KS who developed Burkitt lymphoma (BL). Genetic analysis revealed the presence of a novel heterozygous mutation in the splice site of the intron 4 of KMT2D gene in both peripheral blood-extracted DNA and tumour cells. In addition, the tumour sample of the patient was positive for the classical somatic chromosomal translocation t(8;14) involving the c-MYC gene frequently identified in BL. We propose that the mutated KMT2D gene contributes to the development of both KS and BL observed in our patient and we suggest that strict surveillance must be performed in KS patients.

Prominent and elongated coccyx, a new manifestation of KBG syndrome associated with novel mutation in ANKRD11.

KBG syndrome is characterized by short stature, distinctive facial features, and developmental/cognitive delay and is caused by mutations in ANKRD11, one of the ankyrin repeat-containing cofactors. After the advent of whole exome sequencing, the number of clinical reports with KBG diagnosis has increased, leading to a revision of the phenotypic spectrum associated with this syndrome. Here, we report a female child showing clinical features of the KBG syndrome in addition to a caudal appendage at the coccyx with prominent skin fold and a peculiar calcaneus malformation. Exons and exon-intron junctions targeted resequencing of SH3PXD2B and MASP1 genes, known to be associated with prominent coccyx, gave negative outcome, whereas sequencing of ANKRD11 whose mutations matched the KBG phenotype of the proband showed a de novo heterozygous frameshift variant c.4528_4529delCC in exon 9 of ANKRD11. This report contributes to expand the knowledge of the clinical features of KBG syndrome and highlights the need to search for vertebral anomalies and suspect this condition in the presence of a prominent, elongated coccyx.

Congenital heart defects in molecularly proven Kabuki syndrome patients.

The prevalence of congenital heart defects (CHD) in Kabuki syndrome ranges from 28% to 80%. Between January 2012 and December 2015, 28 patients had a molecularly proven diagnosis of Kabuki syndrome. Pathogenic variants in KMT2D (MLL2) were detected in 27 patients, and in KDM6A gene in one. CHD was diagnosed in 19/27 (70%) patients with KMT2D (MLL2) variant, while the single patient with KDM6A change had a normal heart. The anatomic types among patients with CHD included aortic coarctation (4/19 = 21%) alone or associated with an additional CHD, bicuspid aortic valve (4/19 = 21%) alone or associated with an additional CHD, perimembranous subaortic ventricular septal defect (3/19 = 16%), atrial septal defect ostium secundum type (3/19 = 16%), conotruncal heart defects (3/19 = 16%). Additional CHDs diagnosed in single patients included aortic dilatation with mitral anomaly and hypoplastic left heart syndrome. We also reviewed CHDs in patients with a molecular diagnosis of Kabuki syndrome reported in the literature. In conclusion, a CHD is detected in 70% of patients with KMT2D (MLL2) pathogenic variants, most commonly left-sided obstructive lesions, including multiple left-sided obstructions similar to those observed in the spectrum of the Shone complex, and septal defects. Clinical management of Kabuki syndrome should include echocardiogram at the time of diagnosis, with particular attention to left-sided obstructive lesions and mitral anomalies, and annual monitoring for aortic arch dilatation.

Extensive molecular analysis suggested the strong genetic heterogeneity of idiopathic chronic pancreatitis.

Rationale: Genetic features of Chronic Pancreatitis (CP) have been extensively investigated mainly testing genes associated to the trypsinogen activation pathway. However, different molecular pathways involving other genes may be implicated in CP pathogenesis. Objectives: 80 patients with Idiopathic CP were investigated using Next Generation Sequencing approach with a panel of 70 genes related to six different pancreatic pathways: premature activation of trypsinogen; modifier genes of Cystic Fibrosis phenotype; pancreatic secretion and ion homeostasis; Calcium signalling and zymogen granules exocytosis; autophagy; autoimmune pancreatitis related genes. Results: We detected mutations in 34 out of 70 genes examined; 64/80 patients (80.0%) were positive for mutations in one or more genes, 16/80 patients (20.0%) had no mutations. Mutations in CFTR were detected in 32/80 patients (40.0%) and 22 of them exhibited at least one mutation in genes of other pancreatic pathways. Of the remaining 48 patients, 13/80 (16.3%) had mutations in genes involved in premature activation of trypsinogen and 19/80 (23.8%) had mutations only in genes of the other pathways: 38/64 patients positive for mutations showed variants in two or more genes (59.3%). Conclusions: Our data, although to be extended with functional analysis of novel mutations, suggest a high rate of genetic heterogeneity in chronic pancreatitis and that trans-heterozygosity may predispose to the idiopathic CP phenotype.

Activating Mutations Affecting the Dbl Homology Domain of SOS2 Cause Noonan Syndrome.

The RASopathies constitute a family of autosomal-dominant disorders whose major features include facial dysmorphism, cardiac defects, reduced postnatal growth, variable cognitive deficits, ectodermal and skeletal anomalies, and susceptibility to certain malignancies. Noonan syndrome (NS), the commonest RASopathy, is genetically heterogeneous and caused by functional dysregulation of signal transducers and regulatory proteins with roles in the RAS/extracellular signal-regulated kinase (ERK) signal transduction pathway. Mutations in known disease genes account for approximately 80% of affected individuals. Here, we report that missense mutations altering Son of Sevenless, Drosophila, homolog 2 (SOS2), which encodes a RAS guanine nucleotide exchange factor, occur in a small percentage of subjects with NS. Four missense mutations were identified in five unrelated sporadic cases and families transmitting NS. Disease-causing mutations affected three conserved residues located in the Dbl homology (DH) domain, of which two are directly involved in the intramolecular binding network maintaining SOS2 in its autoinhibited conformation. All mutations were found to promote enhanced signaling from RAS to ERK. Similar to NS-causing SOS1 mutations, the phenotype associated with SOS2 defects is characterized by normal development and growth, as well as marked ectodermal involvement. Unlike SOS1 mutations, however, those in SOS2 are restricted to the DH domain.

Diagnosis of Noonan syndrome and related disorders using target next generation sequencing.

BACKGROUND: Noonan syndrome is an autosomal dominant developmental disorder with a high phenotypic variability, which shares clinical features with other rare conditions, including LEOPARD syndrome, cardiofaciocutaneous syndrome, Noonan-like syndrome with loose anagen hair, and Costello syndrome. This group of related disorders, so-called RASopathies, is caused by germline mutations in distinct genes encoding for components of the RAS-MAPK signalling pathway. Due to high number of genes associated with these disorders, standard diagnostic testing requires expensive and time consuming approaches using Sanger sequencing. In this study we show how targeted Next Generation Sequencing (NGS) technique can enable accurate, faster and cost-effective diagnosis of RASopathies. METHODS: In this study we used a validation set of 10 patients (6 positive controls previously characterized by Sanger-sequencing and 4 negative controls) to assess the analytical sensitivity and specificity of the targeted NGS. As second step, a training set of 80 enrolled patients with a clinical suspect of RASopathies has been tested. Targeted NGS has been successfully applied over 92% of the regions of interest, including exons for the following genes: PTPN11, SOS1, RAF1, BRAF, HRAS, KRAS, NRAS, SHOC, MAP2K1, MAP2K2, CBL. RESULTS: All expected variants in patients belonging to the validation set have been identified by targeted NGS providing a detection rate of 100%. Furthermore, all the newly detected mutations in patients from the training set have been confirmed by Sanger sequencing. Absence of any false negative event has been excluded by testing some of the negative patients, randomly selected, with Sanger sequencing. CONCLUSION: Here we show how molecular testing of RASopathies by targeted NGS could allow an early and accurate diagnosis for all enrolled patients, enabling a prompt diagnosis especially for those patients with mild, non-specific or atypical features, in whom the detection of the causative mutation usually requires prolonged diagnostic timings when using standard routine. This approach strongly improved genetic counselling and clinical management.

DNA methylation profiling in Kabuki syndrome: reclassification of germline KMT2D VUS and sensitivity in validating postzygotic mosaicism.

Autosomal dominant Kabuki syndrome (KS) is a rare multiple congenital anomalies/neurodevelopmental disorder caused by heterozygous inactivating variants or structural rearrangements of the lysine-specific methyltransferase 2D (KMT2D) gene. While it is often recognizable due to a distinctive gestalt, the disorder is clinically variable, and a phenotypic scoring system has been introduced to help clinicians to reach a clinical diagnosis. The phenotype, however, can be less pronounced in some patients, including those carrying postzygotic mutations. The full spectrum of pathogenic variation in KMT2D has not fully been characterized, which may hamper the clinical classification of a portion of these variants. DNA methylation (DNAm) profiling has successfully been used as a tool to classify variants in genes associated with several neurodevelopmental disorders, including KS. In this work, we applied a KS-specific DNAm signature in a cohort of 13 individuals with KMT2D VUS and clinical features suggestive or overlapping with KS. We succeeded in correctly classifying all the tested individuals, confirming diagnosis for three subjects and rejecting the pathogenic role of 10 VUS in the context of KS. In the latter group, exome sequencing allowed to identify the genetic cause underlying the disorder in three subjects. By testing five individuals with postzygotic pathogenic KMT2D variants, we also provide evidence that DNAm profiling has power to recognize pathogenic variants at different levels of mosaicism, identifying 15% as the minimum threshold for which DNAm profiling can be applied as an informative diagnostic tool in KS mosaics.

Immune dysregulation in Kabuki syndrome: a case report of Evans syndrome and hypogammaglobulinemia.

Kabuki syndrome (KS) is a rare multisystemic disease due to mutations in the KMT2D or KDM6A genes, which act as epigenetic modulators of different processes, including immune response. The syndrome is characterized by anomalies in multiple organ systems, and it is associated with autoimmune and inflammatory disorders, and an underlying immunological phenotype characterized by immunodeficiency and immune dysregulation. Up to 17% of KS patients present with immune thrombocytopenia characterized by a severe, chronic or relapsing course, and often associated to other hematological autoimmune diseases including autoimmune hemolytic anemia, eventually resulting in Evans syndrome (ES). A 23-year-old woman, clinically diagnosed with KS and presenting from the age of 3 years with ES was referred to the Rare Diseases Centre of our Pediatric Department for corticosteroid-induced hyperglycemia. Several ES relapses and recurrent respiratory infections in the previous years were reported. Severe hypogammaglobulinemia, splenomegaly and signs of chronic lung inflammation were diagnosed only at the time of our observation. Supportive treatment with amoxicillin-clavulanate prophylaxis and recombinant human hyaluronidase-facilitated subcutaneous immunoglobulin replacement were immediately started. In KS patients, the failure of B-cell development and the lack of autoreactive immune cells suppression can lead to immunodeficiency and autoimmunity that may be undiagnosed for a long time. Our patient's case is paradigmatic since she presented with preventable morbidity and severe lung disease years after disease onset. This case emphasizes the importance of suspecting immune dysregulation in KS. Pathogenesis and immunological complications of KS are discussed. Moreover, the need to perform immunologic evaluations is highlighted both at the time of KS diagnosis and during disease follow-up, in order to allow proper treatment while intercepting avoidable morbidity in these patients.

Biallelic truncating variants in children with titinopathy represent a recognizable condition with distinctive muscular and cardiac characteristics: a report on five patients.

Background: Monoallelic and biallelic TTN truncating variants (TTNtv) may be responsible for a wide spectrum of musculoskeletal and cardiac disorders with different age at onset. Although the prevalence of heterozygous TTNtv is relatively high in the general population, cardiac phenotyping (mainly cardiomyopathies, CMPs) in biallelic titinopathy has rarely been described in children. Methods: We reviewed the medical records of pediatric patients with biallelic TTNtv and cardiac involvement. Clinical exome sequencing excluded pathogenic/likely pathogenic variants in major CMP genes. Results: Five pediatric patients (four male) with biallelic TTNtv were included. Major arthrogryposis multiplex was observed in four patients; no patient showed intellectual disability. At a cardiac level, congenital heart defects (atrial and ventricular septal defects, n = 3) and left ventricular non-compaction (n = 1) were reported. All patients had dilated cardiomyopathy (DCM) diagnosed at birth in one patient and at the age of 10, 13, 14, and 17 years in the other four patients. Heart rhythm monitoring showed tachyarrhythmias (premature ventricular contractions, n = 2; non-sustained ventricular tachycardia, n = 2) and nocturnal first-degree atrio-ventricular block (n = 2). Cardiac magnetic resonance (CMR) imaging was performed in all patients and revealed a peculiar late gadolinium enhancement distribution in three patients. HyperCKemia was present in two patients and end-stage heart failure in four. End-organ damage requiring heart transplantation (HT) was indicated in two patients, who were operated on successfully. Conclusion: Biallelic TTNtv should be considered when evaluating children with severe and early-onset DCM, particularly if skeletal and muscular abnormalities are present, e.g., arthrogryposis multiplex and congenital progressive myopathy. End-stage heart failure is common and may require HT.