Association of mannose-binding lectin promoter gene polymorphism with frequency of vaso-occlusive events in sickle cell disease patients: a single-center Egyptian study

Background
Sickle cell disease leads to hemolytic anemia, vaso-occlusion, and ischemia-reperfusion injury. The mannose-binding lectin (MBL) gene encodes MBL protein that plays a key role in the innate immune system. Genotypes with low serum MBL could lead to increased inflammation, which could contribute to vaso-occlusive crisis (VOC).


Aim
To study MBL promoter gene polymorphisms (MBL-221(X/Y) rs7096206 and MBL-550 (H/L) rs10031251) among 88 Egyptian sickle cell disease patients and its association with serum MBL and disease-related characteristics.


Patients and methods
Genotyping was performed using PCR–restriction fragment length polymorphism technique. Steady-state serum MBL was assayed by enzyme-linked immune sorbent assay (values <500 ng/ml considered deficient).


Results
Comparing studied genotypes and alleles according to serum MBL and disease characteristics showed no significant differences. Low serum MBL was more frequent in SS than Sβ (89.4 vs. 70%) (P=0.023), with 72/88 being deficient. Deficient patients showed significantly higher age, disease duration, VOC per year, and lifetime, and higher VOC index. Serum MBL correlated negatively with patients’ age, disease duration, hydroxyurea treatment duration, lifetime transfusions, HbS, and white cell count (P<0.001, P<0.001, P=0.011, P=0.014, P=0.031, and P=0.040, respectively) and positively with HbF (P=0.002).


Conclusion
Low serum MBL rather than promotor genotypes contributed to clinical outcomes, which were associated with a more severe and long-standing course.