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Most celiac patients failing a gluten-free diet are not refractory; they are eating hidden gluten or have a coexisting condition, so a structured non-responsive differential precedes any refractory workup. When refractory disease is genuine, the type one versus type two split on intraepithelial lymphocyte phenotype separates a steroid-responsive disease with good survival from a pre-lymphoma syndrome. The malignancy spectrum, enteropathy-associated T-cell lymphoma, ulcerative jejunitis, and small-bowel adenocarcinoma, is the payoff of getting that distinction right.
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Welcome to Board Pearls. This is episode two of two of the Celiac and Sprue Spectrum chapter, in the Stomach and Small Bowel Disorders module. This episode is refractory celiac and the complications: the two types of refractory disease and the malignancies that follow.
Start with the picture the boards keep returning to. A patient with proven celiac, on what they call a strict gluten-free diet, comes back with persistent diarrhea, weight loss, and ongoing malabsorption. The temptation is to call it refractory disease and start steroids, and that's almost always wrong, because true refractory celiac is rare and most patients presenting this way have a fixable explanation. So the first move is the differential of non-responsive celiac, not a refractory workup, and it runs in a fixed order.
First and most common is incorrect or incomplete gluten avoidance, covering intentional lapses, unrecognized contamination, and hidden gluten in medications and processed foods, and this alone accounts for most non-responsive cases, so the right next step isn't a biopsy, it's a dietitian going through the actual diet line by line. Second is an incorrect original diagnosis, because a patient labeled celiac on a single weak serology or equivocal biopsy may have had something else all along, so you go back and confirm the serology, the compatible HLA, and a review of the original slides before invoking refractory disease. Third is an unrecognized coexisting condition producing the symptoms while the celiac itself is in remission, with microscopic colitis the high-yield entry, since it's far more common in celiac, so a celiac with watery diarrhea and a healed duodenum needs a colonoscopy with random biopsies; then pancreatic insufficiency, flagged by a low fecal elastase and treated with enzymes, bacterial overgrowth, and the usual IBS and food-intolerance overlaps. Fourth is a medication-induced enteropathy that mimics active celiac, with olmesartan the must-know offender along with NSAIDs and mycophenolate, so a medication review is part of the workup. Only after all of that is exhausted does refractory celiac apply.
Now suppose it really is exhausted: the dietitian has verified strict avoidance, there's no colitis, no pancreatic insufficiency, no overgrowth, no offending drug, and repeat biopsy still shows villous atrophy after at least a year of diet. That's refractory celiac, and the single decision that matters is type one versus type two, made on the phenotype of the intraepithelial lymphocytes, because it separates a steroid-responsive disease with good survival from a pre-lymphoma syndrome with high mortality. Same patient, same histology, same adherence, but two different diseases with two different treatments and prognoses.
Because the phenotyping carries all the weight, you have to know how it's done: the duodenal biopsies for flow cytometry must go into saline or a tissue medium, not formalin, because formalin destroys the surface markers the flow needs to read. So at endoscopy you take extra biopsies, some in saline for flow cytometry, some in formalin for routine histology, plus a sample for the T-cell clonality study. In type one, the lymphocytes are polyclonal and keep their normal phenotype, expressing surface CD3 and CD8, with the abnormal fraction, the cells that have lost those surface markers but kept cytoplasmic CD3, making up less than twenty percent of the population, and the clonality study is polyclonal. Clinically it behaves like an aggressive conventional celiac that hasn't responded to diet alone, and it's treated with the diet plus open-capsule budesonide, with most patients responding, and high-dose prednisone, a thiopurine, or infliximab for the failures, checking TPMT before a thiopurine. Its prognosis is good, which is the whole reason to make the distinction.
In type two, the abnormal clonal lymphocytes exceed twenty percent of the population, and the defining cytometric fact is that phenotype: loss of surface CD3 and CD8 with retained cytoplasmic CD3, and a monoclonal T-cell clonality study. That's essentially a cryptic intraepithelial T-cell lymphoma, and the biology producing it is the same lymphocyte-driving signal as ordinary celiac, but chronic and unchecked, so over years an abnormal compartment persists and a single clone escapes control to become the substrate for the lymphoma that follows. So type two isn't treated as conventional refractory disease: the diet continues and steroids can give symptom control, but the disease-modifying therapy targets the abnormal clone, with cladribine the most established, followed by autologous stem cell transplant in fit responders, and many patients need parenteral nutrition because the malabsorption is severe. Its mortality stays high, largely from progression to frank lymphoma, so type two is managed at tertiary centers and is essentially a pre-lymphoma diagnosis.
That sets up the malignancies, and the organizing fact is that the lymphoma risk is concentrated in refractory disease, especially type two, and in poorly controlled or unrecognized disease, with a strict diet lowering the risk but not eliminating it. The two highest-stakes cancers are enteropathy-associated T-cell lymphoma and small-bowel adenocarcinoma, and both present as a worsening or relapsing celiac picture in a patient who'd been doing well.
The T-cell lymphoma arises out of refractory type two, which is why the type-two-versus-type-one distinction matters so much, since type two progresses to lymphoma far more often. It's uncommon overall but much more frequent in celiac than in the general population, peaks in older age, and is typically jejunal and multifocal with ulceration and sometimes a mass. The catch is that it mimics celiac relapse: a patient doing well on a strict diet develops worsening diarrhea, weight loss, pain, fevers, or unexplained anemia, and the transglutaminase antibody can stay negative because the lymphoma is unrelated to the gluten antibody response, so the differential of celiac relapse despite a strict diet has to include this lymphoma alongside dietary error and refractory disease. B symptoms, a high LDH, a jejunal mass or wall thickening on imaging, and mesenteric nodes raise suspicion, and the diagnostic tools are capsule endoscopy and CT or MR enterography followed by balloon-assisted enteroscopy for targeted biopsy, with capsule particularly useful for finding the multifocal ulcers and masses. Treatment is anthracycline-based chemotherapy with autologous transplant in fit patients, and the prognosis remains poor.
Ulcerative jejunitis sits right next to it on the same biology: multiple discrete chronic jejunal ulcers, often with strictures, bleeding, or obstruction, whose underlying lymphocytes show the same abnormal clonal phenotype as refractory type two. It frequently coexists with or precedes the lymphoma and is best understood as the same pre-lymphoma biology presenting as focal ulcers rather than a mass, so the classic vignette is a celiac on a strict diet with worsening pain, bleeding, or obstruction, where capsule or enteroscopy shows multiple jejunal ulcers without a discrete mass. Treatment is the same as type two, with surgery for the complications.
So hold the lymphoma, the ulcerative jejunitis, and refractory type two together as one continuum: type two is the diagnosis when the abnormal clonal lymphocytes are present with no discrete lesion, ulcerative jejunitis is the same biology presenting as multifocal ulcers, and the lymphoma is the same biology presenting as a large-cell tumor. Capsule endoscopy is the first imaging move in any patient worsening despite a strict diet, surveying the whole small bowel to find where on that continuum they sit, with CT or MR enterography complementing it and device-assisted enteroscopy following for biopsy.
Small-bowel adenocarcinoma is the second malignancy and behaves differently. Its relative risk is markedly elevated but the absolute incidence is low, and unlike the lymphoma it isn't typically preceded by refractory disease, arising even in otherwise well-controlled celiac, particularly with longstanding disease, late diagnosis, or persistent atrophy. It's usually jejunal, reflecting the chronically inflamed mucosa as the substrate, and presents obstructively or with iron-deficiency anemia from occult blood loss, diagnosed by enterography, capsule, and enteroscopy, and treated with resection and adjuvant chemotherapy. A few other cancers carry modestly raised risk too, and the fact that strict adherence reduces the overall malignancy risk is one of the strongest arguments for diagnosis and adherence even in silent or mild disease.
On surveillance: uncomplicated celiac doesn't get routine cancer screening beyond age-appropriate measures and the two-year healing biopsy from the last episode. You intensify imaging and endoscopy in two situations, refractory disease especially type two, where you add enterography and capsule to monitor for the lymphoma and ulcerative jejunitis, and unexplained worsening in an otherwise stable patient, where enterography plus capsule is the next step to look for occult lymphoma, ulcerative jejunitis, or adenocarcinoma. The principle is that the lymphoma risk is concentrated in refractory disease and that capsule and small-bowel imaging are the high-yield tools when the differential opens up. And beyond malignancy, poorly controlled celiac carries persistent nutritional deficiencies, bone disease and fracture risk, liver involvement, and reproductive consequences, plus the associated autoimmune diseases, so the argument for strict adherence is broader than symptom control.
So pull it together. The celiac patient not responding to the diet is, in most cases, eating gluten without knowing it, so the first move is a dietitian and the structured differential of non-responsive disease, running through incorrect adherence, incorrect original diagnosis, coexisting colitis, pancreatic insufficiency, overgrowth, drug-induced enteropathy, and IBD before refractory disease is invoked. When refractory disease is genuinely present, the decision that matters is the lymphocyte phenotype on flow cytometry of biopsies sent in saline rather than formalin: type one keeps the normal surface markers with an abnormal fraction under twenty percent, responds to open-capsule budesonide, and has a good prognosis, while type two has more than twenty percent abnormal clonal lymphocytes that have lost the surface markers, a monoclonal clonality study, and is essentially a pre-lymphoma diagnosis treated with cladribine and transplant at a tertiary center. The malignancy spectrum has three entries: the T-cell lymphoma arising out of type two, ulcerative jejunitis as the multifocal ulcerative version of the same biology, and small-bowel adenocarcinoma behaving separately in even well-controlled disease. The unifying signal is worsening of an otherwise stable celiac course on a verified diet, and the unifying first imaging move is capsule endoscopy with enterography.
That closes the celiac chapter. Chapter eleven takes up what to do when a biopsy shows enteropathy but the celiac serology is negative and the HLA is incompatible, covering non-celiac gluten sensitivity, autoimmune enteropathy, Whipple disease, the drug-induced enteropathies with olmesartan as the headline offender, checkpoint inhibitor enteritis, and tropical sprue, shifting the question from how to diagnose celiac to how to think about everything that looks like celiac and isn't.