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Context: Silver-Russell Syndrome (SRS) is a growth retardation disorder characterized by pre- and post-natal growth failure, relative macrocephaly at birth, prominent forehead, body asymmetry, and feeding difficulties. The main molecular mechanisms are imprinting alterations at multiple loci, though a small number of pathogenic variants have been reported in the SRS genes IGF2-PLAG1-HMGA2 and CDKN1C. However, around 40% of clinically suspected SRS cases do not achieve a molecular diagnosis, highlighting the necessity to uncover the underlying mechanism in unsolved cases., Objective: evaluate the frequency of genetic variants in undiagnosed SRS patients (NH-CSS≥4), and investigate whether (epi)genetic patients may be distinguished from genetic patients., Methods: 132 clinically SRS patients without (epi)genetic deregulations were investigated by Whole Exome (n=15) and Targeted (n=117) Sequencing. Clinical data from our cohort and from an extensive revision of literature were compared., Results: pathogenic variants were identified in 9.1% of this cohort: 3% in IGF2, PLAG1, and HMGA2 genes, while 3% in the IGF1R gene, associated with IGF-1 resistance (IGF1RES), an SRS differential diagnosis. Overall, IGF2-PLAG1-HMGA2 and IGF1R account for 3.6% of SRS with NH-CSS score ≥ 4. A clinical cross-comparison of (epi)genetic versus genetic SRS underlined (epi)genotype-phenotype correlation, highlighted the prevalence of body asymmetry and relative macrocephaly in mosaic (epi)genetic SRS and recurrence of genetic familial cases. Furthermore, overlapping features were evidenced in (epi)genetic SRS and IGF1RES patients., Conclusion: Our study explores the frequency of genetic SRS, underscores body asymmetry as distinctive phenotype in (epi)genetic SRS and suggests IGF1R sequencing in SRS diagnostic flow-chart., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Endocrine Society.)

Background: Carnitine palmitoyltransferase II (CPT II) deficiency is a rare inborn error of mitochondrial fatty acid metabolism with autosomal recessive pattern of inheritance. Its phenotype is highly variable (neonatal, infantile, and adult onset) on the base of mutations of the CPT II gene. In affected subjects, long-chain acylcarnitines cannot be subdivided into carnitine and acyl-CoA, leading to their toxic accumulation in different organs. Neonatal form is the most severe, and all the reported patients died within a few days to 6 months after birth. Hereby, we report on a male late-preterm newborn who presented refractory cardiac arrhythmias and acute multiorgan (hepatic, renal, muscular) injury, leading to cerebral hemorrhage, hydrocephalus, cardiovascular failure and early (day 5 of life) to death. Subsequently, extended metabolic screening and target next generation sequencing (NGS) analysis allowed the CPT II deficiency diagnosis., Case Presentation: The male proband was born at 36 + 4 weeks of gestation by spontaneous vaginal delivery. Parents were healthy and nonconsanguineous, although both coming from Nigeria. Family history was unremarkable. Apgar score was 9/9. At birth, anthropometric measures were as follows: weight 2850 g (47th centile, -0.07 standard deviations, SD), length 50 cm (81st centile, + 0.89 SD) and occipitofrontal circumference (OFC) 35 cm (87th centile, + 1.14 SD). On day 2 of life our newborn showed bradycardia (heart rate around 80 bpm) and hypotonia, and was then transferred to the Neonatal Intensive Care Unit (NICU). There, he subsequently manifested many episodes of ventricular tachycardia, which were treated with pharmacological (magnesium sulfate) and electrical cardioversion. Due to the critical conditions of the baby (hepatic, renal and cardiac dysfunctions) and to guarantee optimal management of the arrythmias, he was transferred to the Pediatric Cardiology Reference Center of our region (Sicily, Italy), where he died 2 days later. Thereafter, the carnitines profile evidenced by the extended metabolic screening resulted compatible with a fatty acid oxidation defect (increased levels of acylcarnitines C 16 and C 18 , and low of C 2 ); afterwards, the targeted next generation sequencing (NGS) analysis revealed the known c.680 C > T p. (Pro227Leu) homozygous missense mutation of the CPTII gene, for diagnosis of CPT II deficiency. Genetic investigations have been, then, extended to the baby's parents, who were identified as heterozygous carriers of the same variant. When we meet again the parents for genetic counseling, the mother was within the first trimester of her second pregnancy. Therefore, we offered to the couple and performed the prenatal target NGS analysis on chorionic villi sample, which did not detect any alterations, excluding thus the CPT II deficiency in their second child., Conclusions: CPTII deficiency may be suspected in newborns showing cardiac arrhythmias, associated or not with hypertrophic cardiomyopathy, polycystic kidneys, brain malformations, hepatomegaly. Its diagnosis should be even more suspected and investigated in cases of increased plasmatic levels of creatine phosphokinase and acylcarnitines in addition to kidney, heart and liver dysfunctions, as occurred in the present patient. Accurate family history, extended metabolic screening, and multidisciplinary approach are necessary for diagnosis and adequate management of affected subjects. Next generation sequencing (NGS) techniques allow the identification of the CPTII gene mutation, essential to confirm the diagnosis before or after birth, as well as to calculate the recurrence risk for family members. Our report broads the knowledge of the genetic and molecular bases of such rare disease, improving its clinical characterization, and provides useful indications for the treatment of patients., (© 2024. The Author(s).)