Intestinal inflammation continues in a subset of celiac disease (CD) patients despite a gluten-free diet. Here, by applying multiomic single cell analysis to duodenal biopsies, we find low-grade malignancies with lymphoma driver mutations in refractory CD type 2 (RCD2) patients comprise surface CD3 negative (sCD3-) lymphocytes stalled at an innate lymphoid cell (ILC) - progenitor T cell stage undergoing extensive TCR recombination. In people with refractory CD type 1 (RCD1), who currently lack explanation, we discover sCD3+ T cells with lymphoma driver mutations forming large clones displaying inflammatory and cytotoxic molecular profiles in 6 of 10 individuals, and a single small clone in 1 of 4 active recently diagnosed CD cases. Accumulation of driver-mutated T cells and their sCD3-progenitors may explain chronic, non-responsive autoimmunity. One-Sentence Summary Treatment refractory autoimmunity in celiac disease may be explained by dysregulated T cells and progenitors that have acquired lymphoma-driver mutations.