No abstract

Background Mast cell activation syndrome (MCAS), a recently recognized non-neoplastic mast cell (MC) disease driving chronic multisystem inflammation ± allergy, appears prevalent and thus important. We report the first systematic characterization of a large MCAS population. Method Demographics, comorbidities, symptoms, family histories, and physical exam and laboratory findings were reviewed in 298 retrospective and 115 prospective MCAS patients. Blood samples from prospective subjects were examined by flow cytometry for clonal MC disease and tested for cytokines potentially driving the monocytosis frequent in MCAS. Results Demographically, white females dominated. Median ages at symptom onset/diagnosis were 9/49 years (ranges 0–88/16–92); median time from symptom onset to diagnosis was 30 years (range 1–85). Median numbers of comorbidities/symptoms/family medical issues were 11/20/4 (ranges 1–66/2–84/0–33). Gastroesophageal reflux, fatigue, and dermatographism were the most common comorbidity, symptom, and exam finding. Abnormalities in routine labs were common and diverse but typically modest. The most useful diagnostic markers were heparin, prostaglandin D2, histamine, and chromogranin A. Flow cytometric and cytokine assessments were unhelpful. Conclusions Our study highlights MCAS’s morbidity burden and challenging heterogeneity. Recognition is important given good survival and treatment prospects.

Acute antibody-mediated rejection (AMR) in heart transplantation is often associated with hemodynamic compromise, and is associated with increased mortality and development of accelerated transplant coronary artery disease (TCAD). The diagnosis of AMR has historically been controversial and outcomes with aggressive immunosuppressive therapy including plasmapheresis and cyclophosphamide are poor. Advances in diagnostic techniques like the demonstration of immunopathologic evidence for antibodymediated rejection by deposition of the complement split product C4d in tissue and detection of anti-HLA antibodies by flow cytometry will assist in further characterizing AMR. Immunosuppression targeting B-lymphocytes and use of m-TOR inhibitors to alter the predilection to develop TCAD and improve survival in AMR remains to be proven.

Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease. Overproduction of nitric oxide (NO) has been implicated in its pathogenesis. Several retrospective studies have indicated a correlation between serum nitrate and nitrite (NOx) and disease activity. This measure of NO production can be falsely elevated by exogenous dietary and medication sources of NOx and variably reduced by serum thiols. These variables can make NOx a less reliable tool for studying the role of NO in SLE. Peroxynitrite, a by-product of NO and superoxide, nitrates tyrosine moieties. The resulting 3-nitrotyrosine (3NT) serves as a long-term indicator of NO-mediated protein modifications that is not affected by exogenous sources of NOx or serum thiols. We hypothesized that for these reasons serum 3NT levels would correlate with lupus disease activity more significantly than serum NOx. To address this hypothesis, we prospectively evaluated lupus disease activity, serum protein 3NT levels, and NOx levels in a cohort of lupus patients at 3-month intervals. Serum 3NT correlated with disease activity among African-Americans, while NOx correlated with disease activity among Caucasians. Subjects with active lupus nephritis had higher levels of serum 3NT than those without renal disease. Immunohistochemical analysis of renal biopsies from subjects with active proliferative lupus nephritis revealed renal expression of inducible NO synthase. The results of this study suggest that overproduction of NO may play a pathogenic role in SLE and lupus nephritis. Serum 3NT may be a useful, new tool for studying the contributions of NO to the pathogenesis of SLE.

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