Renal involvement, presence of amyloidosis, and genotype–phenotype relationship in pediatric patients with Familial Mediterranean fever: a single center study

The aim of the study is to investigate how renal involvement is correlated with frequency of amyloidosis, risk factors, and demographic and clinical characteristics in pediatric patients with Familial Mediterranean fever (FMF). Demographic and clinical characteristics and laboratory data of the pediatric patients diagnosed with FMF between 1990 and 2018 were recorded from their files. The diagnosis of patients with amyloidosis (AA) was proven by renal biopsy, and as for patients with non-amyloidosis renal involvement (RI wo AA), amyloidosis could not be detected but they were followed up with the diagnosis of proteinuria and/or hematuria. A total of 1929 FMF pediatric patients were included in the study. About 962 (49.9%) participants were male. There were 134 (6.9%) patients with RI wo AA and 23 (1.2%) patients with AA diagnosed by biopsy. The most common M694V heterozygous/homozygous(het/hom) (31%) mutation was observed. Delay in diagnosis and presence of colchicine resistance were more in patients with RI wo AA and AA (p < 0.05). M694V het/hom mutation was high in both RI wo AA and AA, while the presence of compound heterozygous with M694V mutation was high in RI wo AA (p < 0.01, p = 0.02, p = 0.048, respectively). There was a positive correlation between M694V mutation and monoarthritis/polyarthritis, between compound heterozygous with M694V mutations and presence of chest pain, and between V726A mutation and constipation. Also a negative correlation was found between E148Q and chest pain and between R202Q mutation and monoarthritis/polyarthritis. While M694V mutation increased the risk 2.6 times for AA and 1.7 times for RI wo AA, colchicine resistance increased the risk 33 times for AA and 25 times for RI wo AA.