Objective To examine the associations between vitamins of the methionine-homocysteine cycle (B6, B12, and folate) and homocysteine (Hcys) with metabolic syndrome (MetS) among Mesoamerican children and their adult parents. Design We conducted a cross-sectional study. Exposures were plasma vitamin B6 and B12 concentrations, erythrocyte folate, and plasma Hcys. In children, the outcome was a continuous metabolic risk score calculated through sex- and age-standardization of waist circumference, the homeostatic model assessment for insulin resistance, mean arterial pressure (MAP), serum high-density lipoprotein (HDL) cholesterol, and serum triglycerides. In parents, the outcome was the prevalence of MetS according to the Adult Treatment Panel III criteria. We estimated mean differences in the metabolic risk score and prevalence ratios (PR) of MetS between quartiles of the exposures using multivariable-adjusted linear and Poisson regression models, respectively. Setting Capital cities of Belize, Guatemala, El Salvador, the Dominican Republic, Honduras, Nicaragua, Panama, Costa Rica, and Chiapas State in Mexico. Participants 237 school-age children and 524 parents. Results Among children, vitamin B12 was inversely associated with the metabolic risk score (quartiles 4-1 adjusted difference = –0.13; 95% CI: -0.21, -0.04; P, trend=0.008) through MAP, HDL cholesterol, and triglycerides. By contrast, folate was positively associated with the metabolic risk score (quartiles 4-1 adjusted difference = 0.11; 95% CI: 0.01, 0.20; P, trend=0.02). In adults, vitamin B6 was inversely associated with MetS prevalence whereas vitamin B12 and folate were positively related to this outcome. Conclusions Vitamins of the methionine-homocysteine cycle are associated with metabolic syndrome in different directions. The associations differ between children and adults.

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The patient is a 64-year-old Caucasian woman with idiopathic chronic urticaria who presented to her primary care physician’s office with mucoid otitis media. Medical history was significant for hypertension, hyperlipidaemia, allergic rhinitis, pre-diabetes, gastro-oesophageal reflux, paroxysmal atrial fibrillation, chronic kidney disease, diverticulosis with prior diverticulitis and history of recurrent infections. Her chronic urticaria was initially treated with antibiotics, antihistamines and oral steroids, but later she developed refractory urticaria requiring dapsone with modest improvement. When she presented with mucoid otitis media, immunoglobulin levels were found to be decreased. The pneumococcal vaccine antibody challenge confirmed the diagnosis of common variable immunodeficiency (CVID). Her HIV test was negative. She was started on intravenous immunoglobulin infusions and her chronic urticaria stabilised.In patients with chronic urticaria refractory to treatment, especially with a history of recurrent infections, a diagnosis of CVID should be considered, regardless of HIV status.