We hereby present a case of an asymptomatic, 72-year-old man who underwent a colonoscopy in 2011 in our open-access endoscopy unit, after being referred by his General Practitioner (GP). The patient had undergone 3 colonoscopies in the previous 3 years (in other open-access units), the first one for bowel cancer screening in 2007 and the rest for surveillance after endoscopic removal of adenomatous polyps (most of them tubular adenomas with low-grade dysplasia). All of them had shown endoscopically mild colitis and histologically dense infiltration of the lamina propria by eosinophils. The patient had been discharged back to the care of his GP in 2009, without any further investigation, being always asymptomatic. It should be emphasized that he had never had abdominal pain, diarrhea, nausea, vomiting, heartburn or any other GI symptoms. His past medical history included a transurethral prostatectomy in 2010 and right inguinal hernia repair in 2006. He had never smoked and he consumed alcohol only on social occasions. There was no family history of importance and he was not on any medication. Clinical examination was unremarkable.
On endoscopy, patchy erythema, edema and nodularity was seen throughout the colon and terminal ileum (Fig. 1A). Few inflammatory polyps were noted in the ascending colon (Fig. 1B). Multiple biopsies were taken, revealing a plethora of eosinophils and mast cells (>15 HPF in aggregates) in lamina propria. Immunohistochemical staining was positive for CD117+ and CD2+ (Fig. 2A, 2B). These findings raised the strong suspicion for SM and further investigations were requested.
Abdominal CT and ultrasound revealed no abnormality. Blood tests showed leukocytosis (total: 13,530/mm3, neutrophils: 10,620/mm3, lymphocytes: 1,530/mm3, monocytes: 780/mm3, eosinophils: 280/mm3), high levels of gamma-globulins (24.90%), beta2-microglobulin (2.81 mg/L) and immunoglobulin IgE (406 IU/mL). Inflammatory markers (CRP, ESR) were normal. Serum total tryptase was 40 ng/mL.
Myelogram revealed reactive bone marrow with predominance of granular series over erythroids (10:1) and marrow infiltration by eosinophils and mast cells (>15/HPF in aggregates, CD117+). Foreign cells were not found and mast cells morphology had no neoplastic characteristics. Bone marrow karyotype was negative for chromosomal abnormalities. Molecular testing of colonic mucosa was positive for the mutation Asp816Val in exon 17 of c-kit gene (DNA amplification and melting curve analysis).
Esophagogastroduodenoscopy and push enteroscopy were performed with normal endoscopic findings. Duodenal and jejunal biopsies showed small bowel mucosa infiltration with eosinophils and mast cells (>15/HPF in aggregates, CD117+, CD2+).
In summary, histology from duodenum, jejunum, ileum, colon and bone marrow revealed mast cells >15/HPF in aggregates and immunohistochemical straining was positive for CD117 and CD2. In accordance with the WHO criteria, this patient was diagnosed with indolent SM, fulfilling one major and two minor criteria (Table 1).
This patient is currently treated prophylactically with H1 and H2 blockers and remains asymptomatic up to the present time. He knows that he should avoid triggers of mast cell degranulation, such as alcohol and venoms. He has regular follow-up appointments in our outpatient clinic.