Proteinuria in cystic fibrosis: a possible correlation between genotype and renal phenotype

Abstract

Objective: To assess proteinuria in patients with cystic fibrosis (CF), and to correlate proteinuria with genotype, CF-related diabetes and disease severity. Methods: A prospective study was carried out over a six-month period and involving 22 CF patients. After the collection and analysis of 24-h urine samples, the patients were divided into two subgroups: protein excretion < 150 mg/day (low-proteinuria); and protein excretion ≥ 150 mg/day (highproteinuria). Patient charts were reviewed to obtain data on genotype and CF-related diabetes. Disease severity was assessed based on acute exacerbations in the last six months and FEV 1 measured during the study period. To assess the correlation between genotype and proteinuria, the two main mutations (ΔF508 and R334W) were evaluated. Due to the existence of genotype ΔF508/R334W, two categories were created to enable statistical analysis, ΔF508 being evaluated in category 1 and R334W being evaluated in category 2. Results: The ΔF508 mutation tended to be associated with normal protein excretion: 100% of the low-proteinuria subgroup patients were considered ΔF508 in category 1, compared with 86.7% in category 2. Protein excretion tended to be higher in patients with the R334W mutation: 60.0% of the high-proteinuria subgroup patients were considered R334W in category 1, compared with 80.0% in category 2 (p = 0.009 and p = 0.014, respectively). No significant association was found for any of the other variables. Conclusions: The results suggest that genotype is associated with renal phenotype, depending on the mechanism by which the genotype alters the function of the cystic fibrosis transmembrane conductance regulator gene.Keywords: Proteinuria; Cystic fibrosis; Genotype. ResumoObjetivo: Avaliar a proteinúria em pacientes com fibrose cística (FC) e correlacioná-la com o genótipo, com a diabetes relacionada à FC e com a gravidade da doença. Métodos: Estudo prospectivo realizado num período de seis meses com 22 pacientes com FC. Efetuada proteinúria de 24 h com a divisão dos pacientes em dois subgrupos: proteinúria < 150 mg/dia (proteinúria-baixa); e proteinúria ≥ 150 mg/dia (proteinúria-alta). Revisamos os prontuá-rios clínicos para a coleta de informações sobre o genótipo e a presença de diabetes relacionada à FC. A gravidade da doença foi avaliada pelas exacerbações agudas no último semestre e pelo VEF 1 durante o período de estudo. Para avaliar a correlação entre genótipo e proteinúria, consideraram-se as duas principais mutações, ΔF508 e R334W. Dada a existência do genótipo ΔF508/R334W, foram criadas duas categorias para se proceder à avaliação estatística, sendo esse genótipo considerado ΔF508 na categoria 1 e R334W na categoria 2. Resultados: A mutação ΔF508 se associou com valores normais de proteinúria: 100% dos pacientes do subgrupo proteinúria-baixa foram considerados ΔF508 na categoria 1, comparados a 86,7% na categoria 2. Em pacientes com a mutação R334W, os valores de proteinuria foram mais elevados: 60,0% dos pacientes do subgrupo proteinúria-alta for...

Original research articles on the cardiopulmonary system recently appeared in Brazilian clinical and surgical journals

“…Renal function. The renal function in cystic fibrosis patients revealed a possible correlation between genotype and renal phenotype in the presence of proteinuria 123 .…”