Background and Aims: Children with very early onset inflammatory bowel disease [VEO-IBD] represent a unique cohort, often with a severe phenotype that is refractory to conventional medications, and some cases have underlying primary immunodeficiencies. Previous work has identified distinct histopathological patterns in the gastrointestinal tract in patients with primary immunodeficiencies. The aim of this study is to characterise the diagnostic histological findings in patients with VEO-IBD as compared with older onset paediatric IBD, and determine if there are unique pathological changes that can shed light on the driving forces of the disease, particularly immunodeficiencies. Methods: Clinical retrospective chart review, including disease characteristics and endoscopic findings, was performed on all included subjects. Two paediatric pathologists reviewed biopsies from diagnostic upper endoscopies and colonoscopies of subjects with very early onset inflammatory bowel disease and older onset inflammatory bowel disease, to evaluate for the presence of 11 histological features previously associated with inflammatory bowel disease and primary immunodeficiencies. Results: The diagnostic gastrointestinal biopsies of subjects with very early onset inflammatory bowel disease differed from those in older onset paediatric IBD, demonstrated by increased frequency of apoptosis, severe chronic architectural changes, small intestine villous blunting, and eosinophils in the crypts, lamina propria, and surface epithelium. Conclusions:The diagnostic biopsies of children with very early onset inflammatory bowel disease can identify characteristic features that may be important in guiding the diagnostic work-up in this population.

Neonatal heart failure is a rare, poorly-understood presentation of familial dilated cardiomyopathy (DCM). Exome sequencing in a neonate with severe DCM revealed a homozygous nonsense variant in leiomodin 2 (LMOD2, p.Trp398*). Leiomodins (Lmods) are actin-binding proteins that regulate actin filament assembly. While disease-causing mutations in smooth (LMOD1) and skeletal (LMOD3) muscle isoforms have been described, the cardiac (LMOD2) isoform has not been previously associated with human disease. Like our patient, Lmod2-null mice have severe early-onset DCM and die before weaning. The infant’s explanted heart showed extraordinarily short thin filaments with isolated cardiomyocytes displaying a large reduction in maximum calcium-activated force production. The lack of extracardiac symptoms in Lmod2-null mice, and remarkable morphological and functional similarities between the patient and mouse model informed the decision to pursue cardiac transplantation in the patient. To our knowledge, this is the first report of aberrant cardiac thin filament assembly associated with human cardiomyopathy.

Placental mesenchymal dysplasia (PMD) is characterized by placentomegaly and grapelike vesicles resembling a partial molar pregnancy and in most cases, a phenotypically normal fetus. Hepatic mesenchymal hamartoma (HMH) is a benign hamartomatous proliferation of mesenchymal liver tissue. PMD has been associated with HMH. Although rare, in combination, it is known to carry a poorer prognosis than in fetuses without structural abnormalities. There are only a few reported cases of PMD and associated HMH with varying management strategies and outcomes, precluding ascertainment of the most appropriate treatment plan. We present a case of PMD with associated cystic HMH resulting in fetal death. We also reviewed the published literature on this issue and explored possible management strategies to prevent adverse fetal and neonatal outcomes.

Aims Bioprosthetic heart valves (BHV), made from glutaraldehyde-fixed heterograft materials, are subject to more rapid structural valve degeneration (SVD) in pediatric and young adult patients. Differences in blood biochemistries and propensity for disease accelerate SVD in these patients, which results in multiple re-operations with compounding risks. The goal of this study is to investigate the mechanisms of BHV biomaterial degeneration and present models for studying SVD in young patients and juvenile animal models. Methods and Results We studied SVD in clinical BHV explants from pediatric and young adult patients, juvenile sheep implantation model, rat subcutaneous implants, and an ex vivo serum incubation model. BHV biomaterials were analyzed for calcification, collagen microstructure (alignment and crimp), and crosslinking density. Serum markers of calcification and tissue crosslinking were compared between young and adult subjects. We demonstrated that immature subjects were more susceptible to calcification, microstructural changes, and advanced glycation end products formation. In vivo and ex vivo studies comparing immature and mature subjects mirrored SVD in clinical observations. The interaction between host serum and BHV biomaterials leads to significant structural and biochemical changes which impact their functions. Conclusions There is an increased risk for accelerated SVD in younger subjects, both experimental animals and patients. Increased calcification, altered collagen microstructure with loss of alignment and increased crimp periods, and increased crosslinking are three main characteristics in BHV explants from young subjects leading to SVD. Together, our studies establish a basis for assessing the increased susceptibility of BHV biomaterials to accelerated SVD in young patients. Translational Perspective Bioprosthetic heart valves (BHV) are the predominant treatment option for valvular heart diseases. However, the main drawback of BHV is their limited durability. Although it has been widely acknowledged that young patients are more susceptible to BHV degeneration and have shorter implant durations, the underlying mechanisms remain elusive. We examined the BHV degeneration process in clinical BHV explants from young and older patients, juvenile sheep implantation model, rat subcutaneous implant model, and ex vivo serum incubation model. These comprehensive basic to translational studies highlighted that BHV degeneration is significantly associated with age related risk factors. These studies also shed light on understanding the degeneration of a variety of xenografts and lay the foundation for future studies on mitigating device degeneration in young patients.