BTLA and Schwartz-Jampel syndrome: Proportions of BTLA−HVEM− CD4+ cells were significantly enriched in SjS samples (p = 0.0021) along with BTLA+HVEM− (p = 0.0039) and BTLA−HVEM+ cells (p = 0.0268), while BTLA+HVEM+ CD4+ cells were reduced (p < 0.0001).