Congenital nephrotic syndrome, Finnish type: sonographic appearance and pathologic correlation

Update on congenital nephrotic syndromes and the contribution of US

The clinical classification of nephrotic syndrome (NS) is based on age at presentation. However, this classification is arbitrary because the majority of early onset NS has a genetic origin and has a widespread age of onset (from fetal life to several years). The aims of this review are to illustrate the knowledge accumulated on congenital nephrotic syndrome (CNS) in terms of genetics, classification, findings at histology and US-based on a review of the literature.

Prenatal findings in four consecutive pregnancies with fetal Pierson syndrome, a newly defined congenital nephrosis syndrome

OBJECTIVE

To describe the prenatal findings in Pierson syndrome, a newly defined autosomal recessive entity, comprising congenital nephrotic syndrome (CNS) with diffuse mesangial sclerosis and distinct eye abnormalities due to LAMB2 mutations.

METHODS

Serial prenatal ultrasound examinations were performed in four consecutive pregnancies affected by Pierson syndrome in the same family. LAMB2 mutations were demonstrated in retrospect by direct sequencing of the gene in the newborn index patient and three abortuses.

RESULTS

Fetal ultrasound consistently revealed marked renal hyperechogenicity associated with variable degree of pyelectasis. These features were detectable by 15 weeks of gestation in all fetuses. Hydrops fetalis due to severe hypalbuminemia demonstrated by chordocentesis occurred in one fetus. Placentas were significantly enlarged. Development of oligohydramnios indicated prenatal decline of renal excretory function. Anencephaly was detected in another fetus with molecularly proven Pierson syndrome at 12 weeks of gestation.

CONCLUSION

We conclude that Pierson syndrome has to be considered in the differential diagnosis of nephrotic disorders with prenatal onset. Ultrasound criteria for differentiation from the most common type of CNS-congenital nephrosis of the Finnish type (CNF)-are discussed. Because of its prognostic relevance, we advocate molecular genetic testing of LAMB2 in any case of prenatally detected nephrotic syndrome with negative results of NPHS1 mutational screening, especially in the presence of the typical sonomorphologic findings of the kidneys and the development of oligohydramnios.