PTEN and systemic lupus erythematosus: SLE patients with rs145204276 ID/DD genotype have high expression of LncRNA‐GAS5 and low expression of miR‐21 in PBMC, which up‐regulates the expression level of PTEN in serum; on the contrary, SLE patients with rs145204276 II genotype have low expression of LncRNA‐GAS5, high level of miR‐21 and down‐regulate PTEN expression level in serum.