Gary Tran

Alterations in B-cell subsets in pediatric patients with early atopic dermatitis

Background B cells undergo maturation and class‐switching in response to antigen exposure and T‐cell help. Early B‐cell differentiation has not been defined in patients with early‐onset atopic dermatitis (AD). Objective We sought to define the frequency of B‐cell subsets associated with progressive B‐cell maturation and IgE class‐switching. Methods We studied 27 children and 34 adults with moderate‐to‐severe AD (mean SCORAD score, 55 and 65, respectively) and age‐matched control subjects (15 children and 27 adults). IgD/CD27 and CD24/CD38 core gating systems and an 11‐color flow cytometric panel were used to determine the frequencies of circulating B‐cell subsets. Serum total and allergen‐specific IgE (sIgE) levels were measured by using ImmunoCAP. Results Compared with adults, children showed T‐cell predominance in the skin. Circulating CD19+CD20+ B‐cell counts were lower in patients with pediatric AD than in control subjects (24% vs 33%, P = .04), whereas CD3+ T‐cell counts were higher (62% vs 52%, P = .05). A decreased B‐cell/T‐cell lymphocyte ratio with age was observed only in pediatric control subjects (r = −0.48, P = .07). In pediatric patients with AD, a positive correlation was observed between B‐cell/T‐cell ratio and nonswitched memory B‐cell counts (r = 0.42, P = .03). Higher frequencies of positive sIgE levels were seen in pediatric patients with AD (P < .0001). Diverse sIgE levels correlated with SCORAD scores and age of pediatric patients with AD (P < .01). Positive correlations were observed between activated B‐cell and memory T‐cell counts (P < .02). In patients with AD, IgE sensitization to most allergens clustered with age, TH1, TH2, total IgE levels, and B‐cell memory subsets. Conclusions Peripheral B and T cells are altered in pediatric patients with early AD, but T cells predominate in skin lesions.

Early-onset pediatric atopic dermatitis is characterized by T H 2/T H 17/T H 22-centered inflammation and lipid alterations

Background: Although atopic dermatitis (AD) often starts in early childhood, detailed tissue profiling of early‐onset AD in children is lacking, hindering therapeutic development for this patient population with a particularly high unmet need for better treatments. Objective: We sought to globally profile the skin of infants with AD compared with that of adults with AD and healthy control subjects. Methods: We performed microarray, RT‐PCR, and fluorescence microscopy studies in infants and young children (<5 years old) with early‐onset AD (<6 months disease duration) compared with age‐matched control subjects and adults with longstanding AD. Results: Transcriptomic analyses revealed profound differences between pediatric patients with early‐onset versus adult patients with longstanding AD in not only lesional but also nonlesional tissues. Although both patient populations harbored TH2‐centered inflammation, pediatric AD also showed significant TH17/TH22 skewing but lacked the TH1 upregulation that characterizes adult AD. Pediatric AD exhibited relatively normal expression of epidermal differentiation and cornification products, which is downregulated in adults with AD. Defects in the lipid barrier (eg, ELOVL fatty acid elongase 3 [ELOVL3] and diacylglycerol o‐acyltransferase 2 [DGAT2]) and tight junction regulation (eg, claudins 8 and 23) were evident in both groups. However, some lipid‐associated mediators (eg, fatty acyl‐CoA reductase 2 and fatty acid 2‐hydroxylase) showed preferential downregulation in pediatric AD, and lipid barrier genes (FA2H and DGAT2) showed inverse correlations with transepidermal water loss, a functional measure of the epidermal barrier. Conclusions: Skin samples from children and adult patients with AD share lipid metabolism and tight junction alterations, but epidermal differentiation complex defects are only present in adult AD, potentially resulting from chronic immune aberration that is not yet present in early‐onset disease.

The spectrum of manifestations in desmoplakin gene (DSP) spectrin repeat 6 domain mutations: Immunophenotyping and response to ustekinumab

Background The immune abnormalities underlying the ichthyoses are poorly understood. Objective To determine the immunophenotype of an ichthyosis resulting from mutations in the spectrin repeat 6 (SR6) domain of desmoplakin gene (DSP) and target therapy on the basis of molecular pathogenesis. Methods Immunophenotyping was performed by using the blood and skin of a girl with SR6 region DSP mutations causing erythroderma/ichthyosis and cardiomyopathy. Results On the basis of the discovery of T helper 1 and T helper 17/interleukin 23 skewing in the skin and T helper 17/interleukin 22 skewing in blood, ustekinumab therapy was initiated. Ustekinumab was also administered to a boy with an SR6 region DSP mutation and ichthyosis without cardiomyopathy. Both children responded despite previous poor responses to immunosuppressants and retinoids. Limitations Small number of patients and immunophenotyping in only 1 patient. Conclusion An understanding of the molecular basis of inflammation in rare cutaneous disorders can lead to targeted therapy, which promises to be more beneficial than broad immunosuppressants.

Langerhans cell histiocytosis: A neoplastic disorder driven by Ras-ERK pathway mutations

&NA; Langerhans cell histiocytosis (LCH) is a disorder of myeloid neoplasia of dendritic cells that affects 1 in 200,000 children <15 years of age and even fewer adults. LCH presents with a spectrum of clinical manifestations. High‐risk stratification is reserved for infiltration of blood, spleen, liver, and lungs. After decades of debate on the disease pathogenesis, a neoplastic mechanism is now favored on the basis of LCH cell clonality, rare cases of familial clustering, and recent evidence of mutations involving the Ras/Raf/MEK (mitogen‐activated protein kinase kinase)/ERK (extracellular signal‐regulated kinase) pathway in lesional biopsy specimens. Somatic mutations are most often found in BRAF (BRAFV600E in 47.1% of reported patients) and MAP2K1 (21.7%) and uncommonly found in MAP3K1 or ARAF. Increased levels of phospho‐ERK in lesional tissue, activation of Ras/Raf/MEK/ERK signaling with these mutations in vitro, and the mutual exclusivity of these mutations in a given patient suggest a central role for activation of the Ras/Raf/MEK/ERK oncogenic pathway in LCH. Immunohistochemical assessment of lesional tissue using the VE1 BRAFV600E mutation–specific antibody can serve as a screening tool for BRAFV600E‐positive LCH. Case reports suggest that BRAFV600E‐positive LCH unresponsive to standard therapy might respond to B‐Raf‐MEK pathway inhibition, but rigorous randomized clinical trials have yet to be performed.

Ichthyosis molecular fingerprinting shows profound TH17 skewing and a unique barrier genomic signature

Background: Ichthyoses are a group of rare skin disorders lacking effective treatments. Although genetic mutations are progressively delineated, comprehensive molecular phenotyping of ichthyotic skin could suggest much‐needed pathogenesis‐based therapy. Objective: We sought to profile the molecular fingerprint of the most common orphan ichthyoses. Methods: Gene, protein, and serum studies were performed on skin and blood samples from 29 patients (congenital ichthyosiform erythroderma, n = 9; lamellar ichthyosis, n = 8; epidermolytic ichthyosis, n = 8; and Netherton syndrome, n = 4), as well as age‐matched healthy control subjects (n = 14), patients with psoriasis (n = 30), and patients with atopic dermatitis (AD; n = 16). Results: Using criteria of a fold change of greater than 2 and a false discovery rate of less than 0.05, 132 differentially expressed genes were shared commonly among all ichthyoses, including many IL‐17 and TNF‐&agr;–coregulated genes, which are considered hallmarks of psoriasis (defensin beta 4A, kynureninase, and vanin 3). Although striking upregulation of TH17 pathway genes (IL17F and IL36B/G) resembling that seen in patients with psoriasis was common to all patients with ichthyoses in a severity‐related manner, patients with Netherton syndrome showed the greatest T‐cell activation (inducible costimulator [ICOS]) and a broader immune phenotype with TH1/IFN‐&ggr;, OASL, and TH2/IL‐4 receptor/IL‐5 skewing, although less than seen in patients with AD (all P < .05). Ichthyoses lacked the epidermal differentiation and tight junction alterations of patients with AD (loricrin, filaggrin, and claudin 1) but showed characteristic alterations in lipid metabolism genes (ELOVL fatty acid elongase 3 and galanin), with parallel reductions in extracellular lipids and corneocyte compaction in all ichthyoses except epidermolytic ichthyosis, suggesting phenotypic variations. Transepidermal water loss, a functional barrier measure, significantly correlated with IL‐17–regulated gene expression (IL17F and IL36A/IL36B/IL36G). Conclusion: Similar to patients with AD and psoriasis, in whom cytokine dysregulation and barrier impairment orchestrate disease phenotypes, psoriasis‐like immune dysregulation and lipid alterations characterize the ichthyoses. These data support the testing of IL‐17/IL‐36–targeted therapeutics for patients with ichthyosis similar to those used in patients with psoriasis.