Dominant negative variants in IKZF2 cause ICHAD syndrome, a new disorder characterised by immunodysregulation, craniofacial anomalies, hearing impairment, athelia and developmental delay

BACKGROUND

Helios (encoded by IKZF2), a member of the Ikaros family of transcription factors, is a zinc finger protein involved in embryogenesis and immune function. Although predominantly recognised for its role in the development and function of T lymphocytes, particularly the CD4+ regulatory T cells (Tregs), the expression and function of Helios extends beyond the immune system. During embryogenesis, Helios is expressed in a wide range of tissues, making genetic variants that disrupt the function of Helios strong candidates for causing widespread immune-related and developmental abnormalities in humans.

METHODS

We performed detailed phenotypic, genomic and functional investigations on two unrelated individuals with a phenotype of immune dysregulation combined with syndromic features including craniofacial differences, sensorineural hearing loss and congenital abnormalities.

RESULTS

Genome sequencing revealed de novo heterozygous variants that alter the critical DNA-binding zinc fingers (ZFs) of Helios. Proband 1 had a tandem duplication of ZFs 2 and 3 in the DNA-binding domain of Helios (p.Gly136_Ser191dup) and Proband 2 had a missense variant impacting one of the key residues for specific base recognition and DNA interaction in ZF2 of Helios (p.Gly153Arg). Functional studies confirmed that both these variant proteins are expressed and that they interfere with the ability of the wild-type Helios protein to perform its canonical function-repressing IL2 transcription activity-in a dominant negative manner.

CONCLUSION

This study is the first to describe dominant negative IKZF2 variants. These variants cause a novel genetic syndrome characterised by immunodysregulation, craniofacial anomalies, hearing impairment, athelia and developmental delay.

Topical skin adhesives for laceration repair in children

QUESTION

A 4-year-old child presented to my office recently with a 2-cm forehead laceration. The child had needle phobia and was very upset, so suturing in the office might have been very challenging. The parents were also concerned about the use of suture. Can topical skin adhesives (TSAs) be used instead of sutures, and what factors should be considered?

ANSWER

Lacerations in children are common and TSAs are useful alternatives to sutures. They achieve comparable outcomes to suturing in appropriately selected wounds. Appropriate lacerations are small, superficial, appropriately cleaned, and have well approximated edges that are not under tension. Complications such as wound dehiscence and infection are rare and cosmetic outcomes are comparable to sutures. Using TSAs can also save time, minimize patient anxiety, and eliminate the need for suture removal.

Online Cleft Educational Videos: Parent Preferences

OBJECTIVE

Determine what parents of children with cleft lip and palate value in online educational videos and evaluate whether their needs are currently being met.

DESIGN

Focus groups and telephone interviews were used to define parent information needs, followed by an evaluation of whether currently available YouTube videos meet these needs.

SETTING

British Columbia Children's Hospital multidisciplinary cleft clinic.

PARTICIPANTS

Twenty-four parents of children with nonsyndromic cleft lip and palate.

RESULTS

Parents desired videos that are accessible, trustworthy, relatable, and positive. Parents preferred a series of short videos addressing relevant topics as their child grows. Currently available YouTube videos only partially met these needs, with underrepresented topics including hearing, dentition, and surgeries for older children.

CONCLUSIONS

While access and validity of video resources can be improved by directing patients and families to appropriate videos, some parent needs remain unmet.

Nodular fasciitis: A rapidly enlarging destructive periorbital mass in an infant

Purpose

To review the clinical and histopathological features of nodular fasciitis, a rare benign periorbital tumor that mimics orbital malignancy, by presenting a case involving an infant with marked orbital wall erosion requiring repair.

Observations

A 9-month-old boy developed a rapidly growing periorbital mass concerning for a soft tissue malignancy. Computerized tomography (CT) scans showed bony erosion of the lateral orbital wall. Incisional biopsy revealed nodular fasciitis. USP6 gene rearrangement was negative. The tumor was completely excised and the underlying orbital wall defect was repaired with polydioxanone (PDS) plate.

Conclusions and Importance

Nodular fasciitis is a benign periorbital tumor that presents like malignancies and warrants prompt investigations, especially in children. Orbital wall erosion is rare and can be repaired to yield good functional and cosmetic outcome.

Development of an evolutionarily novel structure: fibroblast growth factor expression in the carapacial ridge of turtle embryos

The turtle shell, an evolutionarily novel structure, contains a bony exoskeleton that includes a dorsal carapace and a ventral plastron. The development of the carapace is dependent on the carapacial ridge (CR), a bulge in the dorsal flank that contains an ectodermal structure analogous to the apical ectodermal ridge (AER) of the developing limb (Burke. 1989a. J Morphol 199:363-378; Burke. 1989b. Fortschr Zool 35:206-209). Although the CR is thought to mediate the initiation and outgrowth of the carapace, the mechanisms of shell development have not been studied on the molecular level. Here, we present data suggesting that carapace formation is initiated by co-opting genes that had other functions in the ancestral embryo, specifically those of limb outgrowth. However, there is divergence in the signaling repertoire from that involved in limb initiation and outgrowth. In situ hybridizations with antisense riboprobes derived from Trionyx spiniferous fibroblast growth factor-10 (tfgf10) and Trachemys scripta (T. scripta) fibroblast-growth factor 8 (tfgf8) cDNAs were performed on sections of early T. scripta embryos (< 30 days). Expression of tfgf10 was localized to the mesenchyme subjacent to the ectoderm of the CR. In the chick limb bud, FGF10 is known to be expressed in the early limb-forming mesenchyme and is capable of inducing FGF8 in the AER to initiate the outgrowth of the limb bud. Although the expression of tfgf8 was found in the AER of the developing turtle limb, it was not seen in the CR. Thus, the initiation of the carapace is in agreement with FGF10 expression in the CR, but FGF8 does not appear to have a role in mediating early carapace outgrowth.