Faculty Bibliography

Skin barrier dysfunction has been reported in both atopic dermatitis (AD) and food allergy (FA). However, only one-third of patients with AD have FA. The purpose of this study was to use a minimally invasive skin tape strip sampling method and a multiomics approach to determine whether children with AD and FA (AD FA+) have stratum corneum (SC) abnormalities that distinguish them from AD without FA (AD FA-) and nonatopic (NA) controls. Transepidermal water loss was found to be increased in AD FA+. Filaggrin and the proportion of ω-hydroxy fatty acid sphingosine ceramide content in nonlesional skin of children with AD FA+ were substantially lower than in AD FA- and NA skin. These abnormalities correlated with morphologic changes in epidermal lamellar bilayer architecture responsible for barrier homeostasis. Shotgun metagenomic studies revealed that the nonlesional skin of AD FA+ had increased abundance of Staphylococcus aureus compared to NA. Increased expression of keratins 5, 14, and 16 indicative of hyperproliferative keratinocytes was observed in the SC of AD FA+. The skin transcriptome of AD FA+ had increased gene expression for dendritic cells and type 2 immune pathways. A network analysis revealed keratins 5, 14, and 16 were positively correlated with AD FA+, whereas filaggrin breakdown products were negatively correlated with AD FA+. These data suggest that the most superficial compartment of nonlesional skin in AD FA+ has unique properties associated with an immature skin barrier and type 2 immune activation.

Patients with severe atopic dermatitis (AD) are reported to represent between 10% and 18% of all patients with AD. However, in this subgroup of patients, quality of life is significantly affected and patients may have a number of atopic and nonatopic comorbidities. Treatment of this severe population has often been reactive with inappropriate use of systemic corticosteroids and unapproved immunosuppressants. Recent insights point to the systemic nature of AD, which has important therapeutic implications. Management of severe AD requires a comprehensive approach that incorporates proper diagnosis, assessment of disease severity, and impact on patient's and caregiver's quality of life, along with education regarding the chronic relapsing nature of the disease as well as treatment options. Biologics such as dupilumab offer a novel, targeted therapeutic approach for this systemic disease.

Mastocytosis is a clinically heterogenous disease characterized by mast cell hyperplasia in skin, bone marrow and/or visceral organs. Cutaneous mastocytosis is more frequently observed in children, whereas indolent systemic mastocytosis is more commonly observed in adults. Aggressive systemic presentation, particularly of the neonate, is exceptionally rare. We present a rare case of congenital aggressive systemic mastocytosis. The patient was a 37-week-old male, born by caesarean section owing to hepatosplenomegaly and ascites diagnosed in utero, who exhibited extensive cutaneous and systemic manifestations of mastocytosis at birth. Mutation analysis of c-KIT identified D816V mutation in exon 17. Although initial bilateral bone marrow aspirates demonstrated no mast-cell infiltrates or haematological neoplasm, subsequent bone-marrow biopsies postmortem exhibited multifocal mast-cell aggregates. Clinical course was complicated by bacteraemia and cardiorespiratory failure, leading to death at 10 weeks.

Therapeutic regimens for the treatment and long-term management of AD traditionally had a two-fold objective of decreasing skin inflammation and repairing the defective skin barrier. Essential treatments for AD in children should include topical moisturizers for skin hydration and prevention of flares, topical anti-inflammatory medications (e.g. corticosteroids, calcineurin inhibitors, PDE4 inhibitor), allergen/irritant avoidance, and treatment of skin infections. Treatment regimens should be severity-based, and implemented in a stepwise approach tailored to the individual patient. This stepwise approach includes initial use of emollients, gentle skin care, and escalating to more potent anti-inflammatory treatments as the disease severity increases. Currently available systemic medications should be reserved for the presence of recalcitrance to topical therapies due to associated toxicities. We believe that early treatment of AD is not only essential in treating the skin disease, but also in preventing the development of additional atopic diseases, such as food allergy, asthma and allergic rhinitis. The defective skin barrier of AD permits a route of entry for food and environmental allergens, and upon exposure, keratinocytes secrete TSLP, which activates the T_H2 pathway. This T_H2 differentiation sets off the atopic march and the subsequent diseases that are seen. This review highlights treatment options and strategies in pediatric AD therapy with an emphasis on early therapy. Supporting evidence on the efficacy and safety of each intervention will be discussed.