Search

Recently recognized but likely prevalent, mast cell (MC) activation syndrome (MCAS) presents as heterogeneous chronic multisystem polymorbidity of generally inflammatory ± allergic theme; severity can be disabling. MCAS features aberrant MC reactivity and constitutive MC activation with little MC accumulation [Afrin, Ann Med 48:190-201], distinct from mastocytosis (rare and notable for recurrent KIT codon 816 variants). Studies at Univ. of Bonn [Molderings, Scand J Gastroenterol 42:1045-53 and Immunogenetics 62:721-7] suggest most MCAS patients (pts) bear in peripheral blood (PB) MCs somatic, likely constitutively activating, non-codon-816 variants, and some splicing variants, in mRNA for KIT, the dominant MC regulatory gene (MCRG). Other studies show most mastocytosis, too, bears variants in many MCRGs beyond KIT [e.g., Soverini, Blood 126:4085], suggesting the same is likely in MCAS. Confirmation of MCRG variants in MCAS would spur new direction in research in MCAS and chronic inflammatory diseases (CIDs) possibly born of MCAS [Afrin, Transl Res 174:33-59]. We are studying (UMN IRB-approved protocol 2015NTLS023) mRNA for KIT and other MCRGs in PB MCs from MCAS pts and controls (ctls). Methods: We extracted (Miltenyi CD117 immunomagnetic bead method per Bonn) PB MCs from 20 pts aged 18-50 diagnosed at UMN Jul-Dec 2015 with MCAS per criteria [Molderings, J Hematol Oncol 4:10] which in our experience (>1000 pts) reflects MCAS behavior better than other criteria [Valent, Int Arch Allergy Immunol 157:215-25]. We plan the same for 20 demographically matched ctls meeting rigorous good health criteria to exclude illness possibly from undiagnosed MCAS (9 ctls accrued so far, sequencing pending). Immunohistochemical staining with anti-human-c-kit antibodies (Thermo Scientific RB-9038-R7) confirmed extracts were pure bright CD117/c-kit-positive cells. mRNA was isolated (Qiagen RNeasy) and sequenced (Agilent HiSeq). Variant analysis of reverse-transcribed sequences from 38 genes (selected [Molderings, Crit Rev Oncol Hematol 93:75-89 and other reports] as regulating MC activation (receptor activation, signal transduction, cytokine production/release)) was performed via well-established GATK-based bioinformatic pipelines [Onsongo, BMC Res Notes 7:314], plus kallisto [Bray, Biotechnology 34:525-7] for finding RNA splice variants. Results: Table 1 shows key pt characteristics (families similarly afflicted). Percentages of pts with elevations of various MC mediators tested in diagnosing MCAS were similar to prior report [Zenker, Blood 126:5174]. Exonic RNAseq showed many variants across many MCRGs in all 20 pts (median 11,276 variants per pt across studied genes; median 3,277 per pt were novel) but no recurrent variant signatures. Table 2 shows high- and medium-impact variants (HMIVs, i.e., frameshifts and missenses) found with high confidence (≥20 reads aligned to the region of the variant in all 20 pts); 8 KIT variants found were low impact (3' untranslated region). As ctls are not yet fully accrued, we show comparator allele frequencies from 3 reference datasets. Other HMIVs were found with less confidence ( Discussion: We did not find HMIVs in PB MC KIT mRNA in our pts (we soon will study another 20), but we found all bear many mRNA variants in many MCRGs, requiring further study for significance. Reference datasets may be inadequate comparators, skewed by unrecognized MCAS (suspected prevalence as high as 17% [Molderings, PLoS One 8(9):e76241]), so we are accruing rigorously healthy ctls for similar study. If our ctls are largely devoid of HMIVs in MCRG mRNA from PB MCs (as in [Immunogenetics, op. cit.]), a stronger case will be made that MCAS is primarily a clonal disease, if complicated, heterogeneous, and notwithstanding MC-targeted/activating autoimmunity. Further study of variants will include validation by direct DNA sequencing, characterization, and probing for recurrence in CID-specific MCAS subpopulations. Disclosures No relevant conflicts of interest to declare.

It is well-recognized that Helicobacter pylori infection causes gastrointestinal blood loss and iron deficiency. H. pylori gastritis has also been implicated in iron deficiency refractory to oral iron replacement therapy. Although H. pylori infection is common in multiple populations, less is known about the extent to which H. pylori contributes to iron deficiency in different racial/ethnic groups. To address this question, we tested the serum collected from men aged ≥ 25 y and women ≥ 50 y in the Hemochromatosis and Iron Overload Screening (HEIRS) Study to identify those with iron deficiency (defined as serum ferritin ≤ 12 mg/L [cases]) and iron-replete controls (serum ferritin > 100 mg/L in men, serum ferritin > 50 mg/L in women). All samples were tested for H. pylori IgG antibodies and for antibodies to CagA (cytotoxin-associated gene-bearing strain). We tested 571 cases and 1142 controls. Participants were considered to have evidence of H. pylori infection if they had positive results for both antibodies or for either antibody alone. Participants who did not have a result for either test were excluded. We examined the association between the presence of H. pylori in cases and controls among Caucasians, Asian/Pacific Islanders, African Americans, and Hispanics. Among Caucasians, evidence of H. pylori infection was comparable in cases and controls; 170 of 735 controls (23.1%) and 97 of 363 cases (26.7%), respectively, were positive. Similar results were found in African Americans (56.3% of 144 controls; 55.8% of 77 cases) and Hispanics (66.7% of 159 controls; 59.5% of 79 cases). However, in Asian/Pacific Islanders, the prevalence of H. pylori was higher among cases (62.8% of 51) than controls (44.1% of 102), p=0.029 by the likelihood ratio Chi-Square test. The relative risk (RR) of iron deficiency among those with H. pylori-positivity was significantly greater than in those without (RR, 1.66; 95% CI [1.04, 2.66]). A comparison of subgroups by positivity for IgG or CagA showed that the relative risk of iron deficiency was increased among those with IgG positivity, with or without Cag A positivity (RR, 1.80 and 1.90, respectively), but not among those with CagA positivity alone (RR, 1.00). H. pylori infection is a frequent contributor to iron deficiency but is also common in the general population. Our results indicate that among HEIRS Study Asian/Pacific Islander participants, H. pylori infection is more prevalent in cases with iron deficiency than in controls. In contrast, there was no difference in the prevalence of H. pylori infection between cases and controls among Caucasians, African Americans, and Hispanics. These results have implications for the investigation of iron deficiency in Asians and Pacific Islanders. Disclosures No relevant conflicts of interest to declare.

Abstract 2095 Celiac disease (CD) is an increasingly recognized disorder in Caucasian populations of European origin. Little is known about its prevalence in non-Caucasians. While CD is thought to be a cause of iron deficiency anemia, the extent to which CD contributes to iron deficiency in Caucasians and especially non-Caucasians is unknown. Iron deficiency is one of the most common nutritional deficiencies in both the developed world and in developing countries. Thus, it is important to know the prevalence of CD in different populations and in iron-deficient and iron-replete persons. To answer these questions, we tested serum collected from Caucasian and non-Caucasian men aged ≥ 25 y and women ≥ 50 y in the Hemochromatosis and Iron Overload Screening (HEIRS) Study. In the HEIRS Study, 101,168 participants were screened with serum biochemical tests of iron status, which not only detected participants with iron overload but also identified a unique multiethnic population of participants with iron deficiency. We hypothesized that CD is more common in those with iron deficiency than in iron-replete individuals. We also examined the difference in frequency of CD between Caucasians and non-Caucasians with iron deficiency. Cases with iron deficiency (defined as serum ferritin ≤ 12 μg/L [cases]) and iron-replete controls (serum ferritin > 100 μg/L in men, serum ferritin > 50 μg/L in women) were further evaluated by using a sequential serological testing scheme whereby all samples were tested with an ELISA for human recombinant tissue transglutaminase IgA antibodies, and positive values were confirmed by endomysial antibodies. Those positive for both tests were considered double positives and were presumed to have untreated CD. Those positive for tissue transglutaminase IgA antibodies but not for endomysial antibodies were termed single positives and were considered indeterminate and excluded from analysis. We further hypothesized that low serum ferritin and an appropriate human leukocyte antigen (HLA) variant, may be predictive of CD. We used SNP-based analysis to determine HLA genotype and DQ8, DQ2.2 or DQ4, and DQ2.5 risk variants. Fisher's exact test was used to examine the association between iron−deficient case and control status and the presence of celiac disease. Log-binomial regression was applied to estimate the odds of celiac disease in iron-deficient cases relative to that of controls. A total of 1713 subjects were tested for tissue transglutaminase IgA antibodies. Participants included 1100 Caucasians, 221 African Americans, 153 Asians, and 239 Hispanics. Fourteen of 571 iron-deficient cases were positive for the double serology compared to just one of 1142 controls. All of the seropositive tests were seen in Caucasians and none in the non-Caucasians. Excluding data from participants with indeterminate serological screen results (6 Caucasians, 4 non-Caucasians), we found that CD occurred in 14 of 567 cases (2.5%) and in only 1 of 1136 (0.1%) controls (Fisher's exact test, p=1.92 10−6). CD was more common in Caucasian cases (14 of 363, 4%) than in non-Caucasian cases (0 of 204, p=0.003). Only one Caucasian control and none of the non-Caucasian controls had CD. The odds of CD in individuals with iron deficiency was 28 (3.7, 212.8) times that in controls. Thirteen of 14 iron-deficient cases with CD carried the DQ2.5 variant of the HLA genotype. Presence of DQ2.5 was highly significantly associated with celiac disease status in iron-deficient cases compared to controls (Fisher's exact test, p = 7.183 × 10−8). The results indicate that CD is a small but significant contributor to iron deficiency in Caucasians. CD is very rare in other races, even among individuals with features frequently seen in CD, such as iron deficiency. CD is also rare in Caucasians who are iron replete. CD testing should be considered for adult Caucasian males or post-menopausal females having iron deficiency without evidence of other etiologies such as gastrointestinal blood loss. Patients identified with CD may benefit from appropriate treatment. Disclosures: No relevant conflicts of interest to declare.