Clinical and genetic heterogeneity in familial steroid-sensitive nephrotic syndrome

Guillaume Dorval, Olivier Gribouval, Vanesa Martinez-Barquero, Eduardo Machuca, Marie-Josèphe Tête, Véronique Baudouin, Stéphane Benoit, Imen Chabchoub, Gérard Champion, Dominique Chauveau, Hassib Chehade, Chokri Chouchane, Sylvie Cloarec, Pierre Cochat, Karin Dahan, Jacques Dantal, Yahsou Delmas, Georges Deschênes, Phillippe Dolhem, Dominique Durand, Zelal Ekinci, Khalil El Karoui, Michel Fischbach, Jean-Pierre Grunfeld, Vincent Guigonis, Mongia Hachicha, Julien Hogan, Maryvonne Hourmant, Aurélie Hummel, Nassim Kamar, Thierry Krummel, Didier Lacombe, Brigitte Llanas, Laurent Mesnard, Nabil Mohsin, Patrick Niaudet, Hubert Nivet, Paloma Parvex, Christine Pietrement, Loic de Pontual, Claire Pouteil Noble, David Ribes, Pierre Ronco, Eric Rondeau, Marion Sallee, Michel Tsimaratos, Tim Ulinski, Rémi Salomon, Corinne Antignac, Olivia Boyer

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.