Tissue transglutaminase immunoglobulin A exceeds endomysial antibody in specificity of celiac diagnosis at ≥10 times the upper limit of normal.

OBJECTIVE: Serologic diagnosis using tissue transglutaminase immunoglobulin A (TTG-IgA) and endomysial antibody (EMA) is being integrated into the care of pediatric patients with positive screening for celiac disease. The purpose of this study was to assess the utility of EMA in pediatric patients being considered for serologic diagnosis. METHODS: Patients with TTG-IgA testing performed between May 1, 2022 and April 30, 2023 and with subsequent duodenal biopsy within 6 months were included. TTG-IgA serum samples were frozen and sent for EMA testing and titer. EMA was evaluated for positivity and TTG-IgA (normal <15 u/mL) for elevation <10 times (10x) the upper limit of normal (ULN) and ≥10x ULN (≥150 u/mL). Sensitivity and specificity of EMA and TTG-IgA were calculated using biopsy histology as the gold standard. RESULTS: Four hundred and eighty-six patients were included. The sensitivity and specificity of TTG-IgA ≥15 u/mL was 87.5% and 95.4% while EMA was 77.5% and 97.3%. For patients with TTG-IgA ≥10x ULN the specificity was 99.3%. The positive predictive value of TTG-IgA at ≥10x ULN was 91.4% and for EMA was 83.6%. All three patients with false positive TTG-IgA ≥10x ULN also had false positive EMA, and two of these patients had type 1 diabetes mellitus. CONCLUSIONS: TTG-IgA has greater sensitivity at the screening threshold of ≥15 u/mL and greater specificity and positive predictive value at ≥10x ULN than EMA. TTG-IgA at ≥10x ULN is superior to EMA for the serologic diagnosis of celiac disease.

The Role of Diet in Inflammatory Bowel Disease Onset, Disease Management, and Surgical Optimization.

The concept of using diet as therapy in inflammatory bowel disease is of interest to clinicians and patients. Once considered to play a minor role, diet is now known to not only affect disease onset but may also serve as a therapeutic tool for inducing and maintaining remission and improving surgical outcomes. Further research is needed to fully elucidate how, when, and in whom diet therapies may be best applied to improve clinical and disease outcomes. The aim of this review was to summarize current research findings and serve as a tool to help facilitate patient-clinician conversations.

Clinical presentation and factors associated with gluten exposure in children with celiac disease.

OBJECTIVES: The prevalence of celiac disease (CeD) is increasing, yet it is still underdiagnosed, in part because of its heterogeneous presentation. Diagnostic criteria are evolving and management with strict adherence to a gluten-free diet is challenging for many. We aimed to characterize the clinical presentation of CeD among a large multicenter cohort of pediatric patients and to identify factors associated with gluten-free diet adherence. METHODS: Patients with CeD aged 0-18 years were recruited from 11 United States health centers. Parents completed surveys about gluten-free diet adherence and patient electronic health records were reviewed. Logistic regression analyses were performed to identify risk factors associated with gluten exposure. RESULTS: Charts were reviewed for 460 children with a median age of 6.4 years. Abdominal pain was reported in 57% of the cohort, but diverse symptoms were identified. Parent surveys were completed for 455 participants. Sixty-five (14%) participants were at high risk for gluten exposure based on parental reports of weekly or daily gluten exposure or eating gluten by choice in the past year. Participants under the age of 5 years had a lower risk of gluten exposure, while participants without repeat serology testing 18 months after initial diagnosis were at higher risk of gluten exposure. CONCLUSIONS: In a large, multicenter cohort of pediatric CeD patients, clinical presentation is highly variable, necessitating a high index of suspicion to make a diagnosis. Parent surveys indicate that 14% of patients are at high risk of gluten exposure, with patient age and lack of close follow-up associated with gluten-free diet adherence.

Reverse-engineered exclusive enteral nutrition in pediatric Crohn's disease: A pilot trial.

BACKGROUND: In pediatric Crohn's disease (CD), commercial formulas used as exclusive enteral nutrition (EEN) are effective at inducing remission. This study aims to assess the impact of a whole-food blended smoothie as EEN on CD activity and the intestinal microbiome. METHODS: A 4-week prospective trial assessed the impact of EEN with a whole-food smoothie on newly diagnosed mild-to-moderate active pediatric CD. The smoothie with a multivitamin were developed to meet age-appropriate nutritional requirements. Assessment over 4 weeks included Pediatric Crohn's Disease Activity Index (PCDAI), serum laboratories, fecal calprotectin (FCP), and stool collection for metagenomic shotgun sequencing and microbiota composition analysis. Clinical remission was defined as PCDAI ≤ 10 at week 4. RESULTS: Ten participants were enrolled with median age 14.5 years, and 8 completed the trial. Baseline mean PCDAI was 26.3 ± 9.1 and mean FCP 1149 ± 718 µg/g. At week 4, 80% of participants achieved clinical remission. FCP decreased by over half in 60% of participants, with FCP below 250 µg/g in 60% and below 100 µg/g in 40%. Microbiome analysis showed a significant increase in species richness over 4 weeks (p = 0.01). Compared to baseline, the relative abundance at week 2 and at week 4 was significantly increased for Bifidobacterium and Streptococcus and decreased for Blautia (p < 0.05 for all). CONCLUSION: A whole-food blended smoothie was effective for inducing clinical remission and decreasing FCP in pediatric CD similar to commercial EEN formulas. Further research may give insight into data-driven whole-food dietary approaches for CD management. CLINICALTRIALS: gov NCT03508193.

A tip-predominant distribution of villous intraepithelial lymphocytes is not specific to celiac disease in children with Marsh I lesions.

OBJECTIVES: To assess if the distribution of villous intraepithelial lymphocytes (IELs) in a pediatric cohort with Marsh I histopathology is specific to celiac disease (CeD). METHODS: Multicenter, retrospective case-control study between January 2001 and December 2019 in children (<18 years) with and without CeD with intraepithelial lymphocytosis and normal villous architecture. Pathology specimens were reviewed by 2 study pathologists who were blinded to the final diagnosis. Morphologic features (villous height to crypt depth ratio [Vh:Cd]) and IELs in the villous tip, top, or bottom half of the villus were quantified. RESULTS: Of the 97 children with Marsh I histopathology identified during the study period, 63 were excluded due to an insufficient number of well-oriented villous-crypt complexes or a Vh:Cd less than 2. Villous IELs were measured in 34 cases (14 CeD, 20 non-CeD controls). There was no difference between the non-CeD and CeD groups in the mean IELs at the villous tip (14.0 ± 7.1 vs 11.7 ± 6.0, P = .31), top (46.4 ± 18.4 vs 38.3 ± 10.8, P = .11), or bottom (29.8 ± 16.8 vs 28.5 ± 12.8, P = .80) half of each villus, respectively. CONCLUSIONS: The distribution of IELs in Marsh I lesions is not specific for CeD.

A Clinician's Guide to Gluten Challenge.

Gluten challenge is an essential clinical tool that involves reintroducing or increasing the amount of gluten in the diet to facilitate diagnostic testing in celiac disease (CD). Nevertheless, there is no consensus regarding the applications of gluten timing, dosing, and duration in children. This review aims to summarize the current evidence, discuss practical considerations, and proposes a clinical algorithm to help guide testing in pediatric patients. Childhood development, social circumstances, and long-term health concerns must be considered when identifying a candidate for gluten challenge. Based on previous studies, the authors suggest baseline serology followed by a minimum of 3-6 grams of gluten per day for over 12 weeks to optimize diagnostic accuracy for evaluation of CD. A formal provider check-in at 4-6 weeks is essential so the provider and family can adjust dosing or duration as needed. Increasing the dose of gluten further may improve diagnostic yield if tolerated, although in select cases a lower dose and shorter course (6-12 weeks) may be sufficient. There is consensus that mild elevations in celiac serology (<10 times the upper limit of normal) or symptoms, while supportive are not diagnostic for CD. Current North American Society for Pediatric Gastroenterology, Hepatology and Nutrition guidelines recommend histologic findings of intraepithelial lymphocytosis, crypt hyperplasia, and villous atrophy as the accurate and most appropriate endpoint for gluten challenge.

Children With Celiac Disease Consume Specific Food Additives More Frequently Compared to Children Without Celiac Disease.

BACKGROUND: Gluten-free foods often contain food additives to improve palatability, but the long-term effects on the human gastrointestinal tract are not well known. AIMS: This study aimed to quantify frequency of food additive exposure in children with and without celiac disease (CD). METHODS: Children with and without CD were enrolled and demographic data and three-day diet records were obtained. Foods were classified as gluten-free products (GFP) and "processed food", and were evaluated for presence of select food additives: polysorbate 80, carboxymethylcellulose, xanthan gum, guar gum, soy lecithin, titanium dioxide, carrageenan, maltodextrin, and aluminosilicates. The frequency of exposure was described. RESULTS: Twenty-eight participants were included in final analysis. Children with CD had a higher number of daily exposures to xanthan gum (5.3 ± 3.1 vs 2.3 ± 2.4; p = 0.009), but similar exposures to the other additives. GFP contributed 29% of total calories in the GF diet. Both groups had similar intake of processed foods. Comparing GFP and gluten-containing processed foods, 68% vs. 25% contained at least one food additive of interest (p < 0.0001); in the celiac group, those with higher consumption of GFP tended to have a higher frequency of exposure to food additives (p = 0.09). CONCLUSION: A gluten-free diet and consumption of GFP may contribute to differences in food additive intake; quantifying food additive exposures and their effect on humans requires further study.

To DGP-IgG or not? a comparison of TTG-IgA and DGP-IgG.

BACKGROUND: We assessed the diagnostic utility of deamidated gliadin peptide immunoglobulin G (DGP-IgG) in pediatric patients without immunoglobulin A deficiency who underwent tissue transglutaminase immunoglobulin A (TTG-IgA) screening and biopsy. METHODS: Patients who had TTG-IgA performed in our laboratory had sample frozen over 1.5 y. If a patient underwent biopsy within 6 months of serology, DGP-IgG was performed on frozen sample. All testing was performed on the BioPlex 2200. Biopsies were assigned a modified Marsh-Oberhuber score. The sensitivity, specificity, and positive and negative predictive values were calculated for TTG-IgA and DGP-IgG for values ≥ 15 u/ml, 15-149 u/ml, and ≥ 150 u/ml using biopsy as gold standard. RESULTS: A total of 458 patients were included. Sensitivity and specificity for DGP-IgG ≥ 15 u/ml and Marsh ≥ 2 was 76% and 87.5% and TTG-IgA ≥ 15 was notably higher at 93.3% and 92.2%. Sensitivity and specificity of DGP-IgG were 66% and 88.9% at moderate and 29.3% and 98.4% at high increases. The positive predictive value of DGP-IgG for celiac disease in TTG-IgA negative patients was 2.8%. CONCLUSIONS: Our study suggests DGP-IgG does not add significant value in patients screened for celiac disease.

Personalized Research on Diet in Ulcerative Colitis and Crohn's Disease: A Series of N-of-1 Diet Trials.

INTRODUCTION: Evidence about specific carbohydrate diet (SCD) for inflammatory bowel disease (IBD) is limited. We conducted 54 single-subject, double-crossover N-of-1 trials comparing SCD with a modified SCD (MSCD) and comparing each with the participant's baseline, usual diet (UD). METHODS: Across 19 sites, we recruited patients aged 7-18 years with IBD and active inflammation. Following a 2-week baseline (UD), patients were randomized to 1 of 2 sequences of 4 alternating 8-week SCD and MSCD periods. Outcomes included fecal calprotectin and patient-reported symptoms. We report posterior probabilities from Bayesian models comparing diets. RESULTS: Twenty-one (39%) participants completed the trial, 9 (17%) completed a single crossover, and 24 (44%) withdrew. Withdrawal or early completion occurred commonly (lack of response [n = 11], adverse events [n = 11], and not desiring to continue [n = 6]). SCD and MSCD performed similarly for most individuals. On average, there was <1% probability of a clinically meaningful difference in IBD symptoms between SCD and MSCD. The average treatment difference was -0.3 (95% credible interval -1.2, 0.75). There was no significant difference in the ratio of fecal calprotectin geometric means comparing SCD and MSCD (0.77, 95% credible interval 0.51, 1.10). Some individuals had improvement in symptoms and fecal calprotectin compared with their UD, whereas others did not. DISCUSSION: SCD and MSCD did not consistently improve symptoms or inflammation, although some individuals may have benefited. However, there are inherent difficulties in examining dietary changes that complicate study design and ultimately conclusions regarding effectiveness.

Adjunctive Dietary Therapy Is Associated With Improved Gastrointestinal Symptoms in Steroid-Refractory Gastrointestinal Graft-Versus-Host Disease: A Case Series.

Acute gastrointestinal graft-versus-host disease (GI GVHD) is a complication after hematopoietic stem cell transplant with high morbidity and mortality. In particular, steroid-refractory GI GVHD can be difficult to treat. Recent investigations have revealed that patients after transplant can experience intestinal dysbiosis contributing to the progression of GVHD. Modulation of the gut microbiome through dietary intake could potentially improve the intestinal dysbiosis in GI GVHD. In this case series, we present 3 patients where dietary therapy was used in conjunction with immunosuppression to achieve clinical remission of GI GVHD.

Drivers of Variation in Diagnosis and Management of Eosinophilic Esophagitis: A Survey of Pediatric Gastroenterologists.

BACKGROUND: Widespread variation in the diagnosis and treatment of eosinophilic esophagitis (EoE) has previously been reported among adult gastroenterologists; however, variation in EoE practice in among pediatric populations is poorly characterized. The study objectives were to describe guideline adherence and understand reasons for variation in EoE practice among pediatric gastroenterologists following publication of the updated 2018 international EoE guidelines. METHODS: We developed and administered a 28-item survey to pediatric gastroenterologists via an email listserv using the PEDGI Bulletin Board from 03/2019 to 04/2019. The survey was developed using evidence-based review, expert validation, and cognitive interviews. Survey domains included respondent knowledge of and adherence to published guidelines, diagnostic and management approach and rationale, and participant demographics. Analysis included descriptive statistics and tests for association. RESULTS: A total of 288 pediatric gastroenterologists completed the survey, most of whom practiced in an academic center (73%). More than half (63%) reported knowledge of the 2018 updated guidelines; however, only 52% agreed with them and 50% reported adherence. Respondents who reported not agreeing with updated guidelines cited concerns regarding increasing number of endoscopies (72%), misdiagnosing eosinophilia from reflux (56%), and insufficient data (23%). The most common drivers of decision making with respect to therapy choice were patient/family preference, evidence/guidelines, and symptom burden. CONCLUSIONS: Many physicians are not adherent to current guidelines for reasons which include lack of knowledge of updated guidelines and concern regarding the strength of the supporting evidence. This study elucidates several areas to enhance education regarding these guidelines to promote widespread adherence.

Evaluation of BioPlex 2200 tTG-IgA Diagnostic Performance for Serology-Based Diagnosis of Celiac Disease.

OBJECTIVES: Forgoing biopsy for the diagnosis of celiac disease in children with tissue transglutaminase immunoglobulin A (tTG-IgA) levels greater than or equal to 10 times the upper limit of normal (≥10×ULN) has been advocated by the European Society of Paediatric Gastroenterology, Hepatology and Nutrition. METHODS: Our retrospective study tested the specificity and positive predictive value (PPV) of the BioPlex 2200 assay (Bio-Rad Laboratories) in diagnosing celiac disease at the ≥10×ULN tTG-IgA threshold, which is ≥150 U/mL (negative <15 U/mL). We used the tTG-IgA and duodenal biopsy results within 6 months following tTG-IgA measurements from 542 patients who had any number of duodenal biopsy fragments, of whom 165 patients had 5 or more tissue fragments. Sensitivity and specificity of the test were calculated using histology as the gold standard for Marsh class 2 and above. RESULTS: For histopathologic findings in the duodenum with Marsh 2 and higher, the specificity and PPV of the BioPlex 2200 at ≥10×ULN tTG-IgA were 99.5% and 95.4% using all biopsies and 97.9% and 94.9% for biopsies with 5 or more tissue fragments. CONCLUSIONS: Should clinical considerations preclude endoscopy, the BioPlex 2200 assay at ≥10×ULN TTG-IgA could be considered highly suggestive of disease.

Intermittent antibiotic treatment accelerated the development of colitis in IL-10 knockout mice.

BACKGROUND AND AIMS: Many epidemiological studies suggest an association between antibiotic exposure and the development of inflammatory bowel disease [IBD]. However, the majority of these studies are observational and still the question remains, "Does the specific antibiotic administration regimen play a role in the development of colitis?" This study aimed to compare the possible effects of continuous and intermittent antibiotic exposure on the development of colitis using a colitis-susceptible IL-10 knockout [IL-10-/-] mouse model. METHODS: IL-10-/- mice [C57BL/6] were randomly assigned to a non-antibiotic group, continuous antibiotic group and intermittent antibiotic group, and observed for 30 weeks. The antibiotic cocktail was given via the drinking water. The differential response to antibiotics was assessed. RESULTS: Intermittent antibiotic treatment resulted in severe colitis with early disease onset in IL-10-/- mice. Higher unit colon weight and spleen weight were observed in intermittent antibiotic-treated mice but not in the continuous antibiotic group. Moreover, intermittent antibiotic treatment aggravated epithelial damage and colonic inflammation, mucosal barrier dysfunction and colonic allergic sensitization in IL-10-/- mice, whereas continuous antibiotic treatment ameliorated these symptoms. Male IL-10-/- mice with intermittent antibiotic exposure were more susceptible to colonic inflammation and allergic response than females. CONCLUSIONS: In summary, intermittent antibiotic exposure accelerated the development of severe colitis more than continuous antibiotic exposure in IL-10-/- male mice. In addition to the colonic damage and impaired barrier function, stimulation of allergic response may play a role in accelerating the development of colitis in genetically susceptible mice.

Role of Gut Microbiota in the Anti-Colitic Effects of Anthocyanin-Containing Potatoes.

SCOPE: Anthocyanin-containing potatoes exert anti-inflammatory activity in colitic mice. Gut bacterial dysbiosis plays a critical role in ulcerative colitis. This study examined the extent to which the anti-colitic activity of anthocyanin-containing red/purple-fleshed potatoes depends on the gut bacteria using a chemically-induced rodent model of colitis with the intact and antibiotic-ablated microbiome. METHODS AND RESULTS: Four-week-old male mice (C57BL6) are randomly assigned to the control diet or 20% purple-/red-fleshed potatoes supplemented diet group. The microbiota-ablated group received an antibiotic cocktail in drinking water. At week nine, colitis is induced by 2% dextran sulfate sodium (DSS) in drinking water for five days. Administration of antibiotics resulted in a 95% reduction in gut bacterial load and fecal SCFAs. DSS-induced elevated gut permeability and body weight loss are more pronounced in antibiotic mice compared to non-antibiotic mice. Purple- or red-fleshed potato supplementation (20% w/w) ameliorated DSS-induced reduction in colon length and mucin 2 expression levels, and increase in permeability, spleen weight, myeloperoxidase (MPO) activity, and inflammatory cytokines (IL-6, IL-17, and IL1-ß) expression levels in non-antibiotic mice, but not in gut microbiota ablated mice. CONCLUSIONS: Anthocyanin-containing potatoes are potent in alleviating colitis, and the gut microbiome is critical for the anti-colitic activity of anthocyanin-containing potatoes.

Differences in Nutrient Intake with Homemade versus Chef-Prepared Specific Carbohydrate Diet Therapy in Inflammatory Bowel Disease: Insights into Dietary Research.

PURPOSE: The aim of this study was to evaluate the nutrient content consumed by children and adolescents on home-prepared versus chef-prepared specific carbohydrate diets (SCD) as therapy for inflammatory bowel disease (IBD). METHODS: Dietary intake of two cohorts with active IBD initiating the SCD over 12 weeks was assessed. The home-prepared cohort received detailed guidance from dietitians on implementation of the SCD. The chef in the other cohort was knowledgeable in the SCD and prepared meals from a fixed set of recipes. Data from 3-day diet diaries at 4 different time points were collected. US Recommended Daily Allowances (RDA) were calculated for macronutrients, vitamins, and minerals. RESULTS: Eight participants on the homemade SCD and 5 participants on the chef-prepared SCD were included in analysis. Mean % RDA for energy intake was 115% and 87% for homemade and chef-prepared groups (p<0.01). Mean % RDA for protein intake was 337% for homemade SCD and 216% for chef-prepared SCD (p<0.01). The homemade SCD group had higher mean % RDA values for vitamin A and iron, while the chef-prepared SCD group had higher intake of vitamins B1, B2, D, phosphorus and zinc (p<0.01 for all). CONCLUSION: The SCD implemented homemade versus chef-prepared can result in significantly different intake of nutrients and this may influence efficacy of this dietary therapy. Meal preparation dynamics and the motivation of families who pursue dietary treatment may play an important role on the foods consumed and the outcomes on dietary therapy with the SCD.

Paradoxical Psoriasis in Children Receiving Anti-TNFα Treatment for Inflammatory/autoimmune Disease.

Tumor necrosis factor alpha inhibitors (TNFi) are widely used in children with autoimmune and autoinflammatory conditions. Although TNFi are approved to treat psoriasis, they have also been shown to paradoxically induce psoriasiform lesions. In this review, we aim to focus on the clinical presentation and management of paradoxical psoriasis after exposure to TNFi in children with juvenile idiopathic arthritis (JIA), inflammatory bowel disease (IBD), or chronic nonbacterial osteomyelitis (CNO). A narrative review of the literature was performed given the limited number of publications on this topic. Children with IBD, CNO, and JIA have a higher risk of developing psoriasis at baseline, which increases after TNFi use in those with JIA and IBD. Risk factors for paradoxical psoriasis remain incompletely defined, and patients with IBD and/or CNO develop paradoxical psoriasis more commonly than those with JIA. Sex, race, and family history were not significantly associated with paradoxical psoriasis. The most commonly implicated TNFi include infliximab and adalimumab. Paradoxical psoriasis occurs in a similar distribution on the body to isolated psoriatic lesions and is morphologically indistinguishable. In many instances, topical therapies are effective in treating psoriasis and children can continue on TNFi for their primary disease. If lesions are severe or unacceptable to patients, TNFi may be switched or discontinued. Further research is needed to better characterize risk factors and understand the mechanism of disease pathogenesis. Pediatric health care providers who prescribe TNFi should counsel families regarding the risk of paradoxical psoriasis prior to starting the medication and monitor for new cutaneous eruptions.

Is Endoscopic Assessment of the Esophagus and Stomach Enough to Determine the Need for Biopsy at These Sites in Pediatric Patients Undergoing Endoscopy for Elevated TTG?

OBJECTIVES: The goal of our study was to determine whether visual assessment of the esophagus and stomach could predict abnormal histology and determine the frequency of interventions based on biopsies in patients undergoing endoscopy for elevated tissue transglutaminase immunoglobulin A antibody (TTG). METHODS: Pathology records were searched for patients with biopsy performed for elevated TTG. Pathology report, endoscopy report, and follow-up were obtained and slides from the duodenum reviewed. Pathology was considered gold standard for sensitivity and specificity calculations. RESULTS: 240 patients were included. 215 patients had esophageal biopsies performed. Esophageal endoscopic visual assessment had sensitivity of 47% and specificity of 93% for abnormal histology. 16(7%) patients had therapy or referral related to results and, of these, 6(38%) had visually normal endoscopy. 237 biopsies were performed of stomach. Gastric endoscopic visual assessment had a sensitivity and specificity of 20% and 87%. 24(10%) patients had therapy based on findings and, of these, 12 (50%) had visually normal endoscopy. CONCLUSIONS: Endoscopic assessment of esophagus and stomach has low sensitivity and high specificity for pathologic abnormalities when indication for endoscopy is elevated TTG. When endoscopy is visually normal clinical interventions based on biopsy are rare, and foregoing biopsy may be considered.

Mutations in 3ß-hydroxysteroid-δ8, δ7-isomerase paradoxically benefit epidermal permeability barrier homeostasis in mice.

Inherited or acquired blockade of distal steps in the cholesterol synthetic pathway results in ichthyosis, due to reduced cholesterol production and/or the accumulation of toxic metabolic precursors, while inhibition of epidermal cholesterol synthesis compromises epidermal permeability barrier homeostasis. We showed here that 3ß-hydroxysteroid-δ8, δ7-isomerase-deficient mice (TD), an analog for CHILD syndrome in humans, exhibited not only lower basal transepidermal water loss rates, but also accelerated permeability barrier recovery despite the lower expression levels of mRNA for epidermal differentiation marker-related proteins and lipid synthetic enzymes. Moreover, TD mice displayed low skin surface pH, paralleled by increased expression levels of mRNA for sodium/hydrogen exchanger 1 (NHE1) and increased antimicrobial peptide expression, compared with wild-type (WT) mice, which may compensate for the decreased differentiation and lipid synthesis. Additionally, in comparison with WT controls, TD mice showed a significant reduction in ear thickness following challenges with either phorbol ester or oxazolone. However, TD mice exhibited growth retardation. Together, these results demonstrate that 3ß-hydroxysteroid-δ8, δ7-isomerase deficiency does not compromise epidermal permeability barrier in mice, suggesting that alterations in epidermal function depend on which step of the cholesterol synthetic pathway is interrupted. But whether these findings in mice could be mirrored in humans remains to be determined.