MBL2 and hyperinsulinemic hypoglycemia, familial, 4: Although, MBL deficiency defined as a serum concentration below 0.5 μg/mL was numerically more common in UCTD patients (48.3% vs. 31.3%, p = 0.07), MBL serum concentrations (mean 1.1 vs. 1.5 μg/mL, p = 0.1) and the frequency of MBL2 polymorphisms were similar (data not shown).