Clinical and genetic heterogeneity in familial steroid-sensitive nephrotic syndrome

Familial steroid-sensitive nephrotic syndrome (SSNS) is a rare condition. The disease pathophysiology remains elusive. However, bi-allelic mutations in the EMP2 gene were identified, and specific variations in HLA-DQA1 were linked to a high risk of developing the disease.

Clinical data were analyzed in 59 SSNS families. EMP2 gene was sequenced in families with a potential autosomal recessive (AR) inheritance. Exome sequencing was performed in a subset of 13 families with potential AR inheritance. Two variations in HLA-DQA1 were genotyped in the whole cohort.

Transmission was compatible with an AR (n = 33) or autosomal dominant (AD, n = 26) inheritance, assuming that familial SSNS is a monogenic trait. Clinical features did not differ between AR and AD groups. All patients, including primary (n = 7) and secondary steroid resistant nephrotic syndrone (SRNS), (n = 13) were sensitive to additional immunosuppressive therapy. Both HLA-DQA1 variations were found to be highly linked to the disease (OR = 4.34 and OR = 4.89; p < 0.001). Exome sequencing did not reveal any pathogenic mutation, neither did EMP2 sequencing.

Taken together, these results highlight the clinical and genetic heterogeneity in familial SSNS. Clinical findings sustain an immune origin in all patients, whatever the initial steroid-sensitivity. The absence of a variant shared by two families and the HLA-DQA1 variation enrichments suggest a complex mode of inheritance.