Feingold syndrome (FS) is a rare congenital disorder with an autosomal dominant inheritance pattern. Two distinct subtypes are recognized based on their molecular pathology: FS type 1 (FS1) and FS type 2 (FS2). Both types share skeletal anomalies such as microcephaly, brachymesophalangia, and clinodactyly; however, gastrointestinal atresia is unique to FS1. Herein, we report a rare prenatal diagnosis of FS1 in a female fetus. The second-trimester ultrasound revealed bilateral clinodactyly and fetal microcephaly, and the subsequent molecular karyotyping identified a ~342 kb deletion at 2p24.3 encompassing the MYCN gene, confirming the diagnosis. The same deletion was detected in the father, verifying the hereditary pattern. The pregnancy was also complicated by preeclampsia and fetal growth restriction, leading to preterm caesarean delivery at 33 + 3 weeks of gestation. The neonate had microcephaly and clinodactyly but no gastrointestinal defects. In conclusion, high clinical suspicion aroused by identifying ultrasound features of FS can lead to early prenatal diagnosis via molecular karyotyping. Detecting accompanying gastrointestinal disorders that require early operation is crucial for the prognosis, genetic counseling, and prenatal management of the affected families.

This article presents an overview of the life histories of reared-apart twins from the Philippines. One twin always knew he was a twin, but for the other twin the discovery at age 15 came as a shock. This essay is followed by summaries of recent twin research of interest. Topics include twin discordance for multisystem inflammatory syndrome, in vitro fertilization (IVF) twins and possible associations with impaired hearing, the writings of monozygotic (MZ) twins, and an update on MZ twins with Feingold syndrome whom I have covered in a previous issue of this journal. This essay concludes with several twin-related human interest stories, namely conjoined twin girls from Sri Lanka, conjoined twin boys from Papua, New Guinea, recent information concerning conjoined twins Abby and Brittany Hensel, a twin sentenced for criminal activities, and accurate identification of an identical twin culprit by DNA sequencing.

Mycn, a MYC gene family member, is implicated in both carcinogenesis through amplification and Feingold syndrome through its deficiency. Previous studies have indicated that increased Mycn expression enhances vascularization in human neuroblastomas, yet its precise role in vascular development remains elusive. In this study, we utilized single-cell RNA-seq and live imaging analyses to confirm that mycn is expressed during zebrafish vasculogenesis. We investigated vascular development in zebrafish using a genetically engineered mycn mutation. Our findings reveal that mycn-deficient zebrafish exhibit reduced intersegmental vessels and malformed subintestinal vessels, primarily due to decreased cell proliferation in vascular endothelial cells. Importantly, we discovered that activation of PI3K signaling significantly ameliorates these vascular abnormalities. Our study establishes Mycn as a key regulator of vascular development in zebrafish, acting through the PI3K signaling pathway.

A pair of dizygotic (DZ) twins discordant for Turner syndrome are discussed with reference to the biological origins of the condition and the effects of discordance on the twin relationship. There is little research on how having an atypical twin influences the life events and goals of the typical twin. Next, timely reviews of research on preventing premature twin birth, a twin gestation with hydatidiform mole, an update on Feingold syndrome twins discussed in a previous issue of this journal, and qualitative monozygotic twin difference studies are presented. The final portion of this article covers human interest stories of twins that are variously entertaining and enlightening. They include identical twins who celebrated their 100th birthday together, twins in famous families, celebration of the Yorùbá twins of Nigeria, identical artistic partners, and surgical separation of a rare, conjoined twin set.

Feingold syndrome type 1 (FS1) (OMIM 164280) is an autosomal dominant condition due to heterozygous loss of function variants in MYCN gene or to 2p24 deletion encompassing MYCN gene. The core features of FS1 are digital anomalies, microcephaly, facial dysmorphism, short stature, esophageal/duodenal atresia, and mild learning disabilities. Additional features are reported in a minority of patients, such as cardiac and renal anomalies. Sensorineural deafness is reported in 7 % of the patients. Other features can be associated with classical features of FS1 in patients with 2p deletion including MYCN and other genes. Recently, absence of the flexor pollicis longus tendon has been reported as a new skeletal feature in a pedigree segregating a MYCN variant. Here, we reported on three patients having FS1 without gastrointestinal atresia and unusual features: laryngeal cleft, congenital deafness, agenesis of the corpus callosum, and radio ulnar-synostosis (RUS). After the extension of the genetic screening, RUS was considered as an independent condition linked to SMAD6 variant. Diagnosis of FS1 can be challenging when there are unusual features without digestive malformations drawing attention. In this situation, the diagnostic approach may be based on major criteria of FS1: i) brachymesophalangy of the 2nd and 5th fingers, brachydactyly of fingers and toes with or without 2/3 and/or 4/5 toe syndactylies, ii) microcephaly, and iii) radiographs of the feet to look for amesophalangy of toes. Extension of the genetic screening is required to eliminate the possibility of two independent conditions. In addition to the previous recommendations, we advocate for a set of recommendations for evaluation of FS1 patients following initial diagnosis: systematic search of deafness, verification of the flexion of the interphalangeal joints of the thumbs, laryngoscopy in case of stridor or swallowing disorders, and finally systematic cerebral MRI.