Biallelic loss-of-function LACC1/FAMIN mutations presenting as rheumatoid factor-negative polyarticular juvenile idiopathic arthritis

Rabionet Janssen, Raquel; Remesal, Agustín; Mensa Vilaró, Anna; Murías, Sara; Alcobendas, Rosa; González-Roca, Eva; Ruíz Ortiz, Estíbaliz; Antón, Jordi; Iglesias, Estibaliz; Modesto, Consuelo; Comas, David, 1969-; Puig, Anna; Drechsel, Oliver; Ossowski, Stephan; Yagüe, Jordi L.; Merino, Rosa; Estivill, Xavier, 1955-; Aróstegui Gorospe, Juan Ignacio

doi:http://dx.doi.org/10.1038/s41598-019-40874-2

Biallelic loss-of-function LACC1/FAMIN mutations presenting as rheumatoid factor-negative polyarticular juvenile idiopathic arthritis

Citation

Rabionet R, Remesal A, Mensa-Vilaró A, Murías S, Alcobendas R, González-Roca E et al. Biallelic loss-of-function LACC1/FAMIN mutations presenting as rheumatoid factor-negative polyarticular juvenile idiopathic arthritis. Sci Rep. 2019;9(1):4579. DOI: 10.1038/s41598-019-40874-2

Abstract

Juvenile idiopathic arthritis (JIA) is a complex rheumatic disease with both autoimmune and autoinflammatory components. Recently, familial cases of systemic-onset JIA have been attributed to mutations in LACC1/FAMIN. We describe three affected siblings from a Moroccan consanguineous family with an early-onset chronic, symmetric and erosive arthritis previously diagnosed as rheumatoid factor (RF)-negative polyarticular JIA. Autozygosity mapping identified four homozygous regions shared by all patients, located in chromosomes 3, 6 (n:2) and 13, containing over 330 genes. Subsequent whole exome sequencing identified two potential candidate variants within these regions (in FARS2 and LACC1/FAMIN). Genotyping of a cohort of healthy Moroccan individuals (n: 352) and bioinformatics analyses finally supported the frameshift c.128_129delGT mutation in the LACC1/FAMIN gene, leading to a truncated protein (p.Cys43Tyrfs*6), as the most probable causative gene defect. Additional targeted sequencing studies performed in patients with systemic-onset JIA (n:23) and RF-negative polyarticular JIA (n: 44) revealed no pathogenic LACC1/FAMIN mutations. Our findings support the homozygous genotype in the LACC1/FAMIN gene as the defect underlying the family here described with a recessively inherited severe inflammatory joint disease. Our evidences provide further support to the involvement of LACC1/FAMIN deficiency in different types of JIA in addition to the initially described systemic-onset JIA.