Does breast-feeding affect severity of familial Mediterranean fever?

Familial Mediterranean fever (FMF) is the most common inherited autoinflammatory disease, which is caused by an inborn error in innate immune system. It was shown that disease severity of patients of the same ethnic origin differed according to different country of residence, suggesting an influence of environment on phenotype of FMF. Different microbial milieus of the countries were accused. Breast-feeding has an important role on innate immunity and protects the infant from infections. The aim of this study is to investigate whether being breast-fed and duration of breast-feeding has an impact on disease severity of FMF. The mothers of patients were asked to fill a questionnaire about the feeding type in infancy. Mode of delivery, gestational age, and age at onset of FMF symptoms were also asked. The disease severity score of each patient was calculated according to the scoring system suggested by Pras et al. (Am J Med Genet 75:216-219, 1998). MEFV mutations were noted. The mothers of 81 FMF patients completed the questionnaire. Fifteen patients (18.5%) had mild, 49 (60.5%) had moderate, and 17 (21%) had severe disease. All the patients except four were breast-fed for some period. The duration of breast-feeding was similar between three severity groups. Time to introduce cow's milk and complementary foods also did not differ between groups. Longer duration of breast-feeding did not delay the onset of FMF symptoms. Mode of delivery and gestational age had no effect on disease severity. Patients homozygous for M694V had higher severity scores. This preliminary study suggests that breast-feeding is not an exogenous factor having an influence on phenotype of FMF. M694V genotype seems to cause more severe disease.