Mutations of FAM111B gene are not associated with Systemic Sclerosis

Systemic sclerosis (SSc) is a prototypic systemic fibrotic disease with unclearly characterized genetic basis. We have discovered that mutations in family with sequence similarity 111, member B (FAM111B) gene cause hereditary fibrosing poikiloderma with tendon contractures, myopathy, and pulmonary fibrosis, a multisystem fibrotic condition with clinical similarities to SSc. This observation has established FAM111B as a candidate gene for SSc. Patients and Methods: Demographic and clinical characteristics of consenting adults with definite SSc were recorded. Blood DNA analysis was performed using the High-Resolution Melt technique, and samples with abnormal electropherograms were selected for Sanger sequencing to identify mutations. Ethnically-matched controls from the general South African population were used to verify the frequency of variants in FAM111B. Public databases such as 1000 Genomes and ExAC were also used to verify the frequency of variants in FAM111B. Results: Of 131 patients, 118 (90.1%) were female, and 78 (59.5%) were black Africans. Genetic analysis revealed two FAM111B genetic variants. The c.917 A > G variant (rs200497516) was found in one SSc patients, and one control, and was classified as a missense variant of unknown significance. The c.988 C > T variant (rs35732637) occurred in three SSc patients and 42/243 (17.3%) of healthy controls, and is a known polymorphism. Conclusion: One rare variant was found in a patient with SSc but has no functional or structural impact on the FAM111B gene. In this cohort, FAM111B gene mutations are not associated with SSc.