Abstract
Introduction/Objective
Mastocytosis is a rare disease in which there are abnormal mast cell accumulation in one or more tissue sites. Multifocal dense mast cell aggregates with atypical morphology or immunohistochemistry are considered as systemic mastocytosis (SM) based on WHO criteria. SM usually involves bone marrow and majority of them also have KIT mutation. There are rare case reports of atypical enterocolic mast cell aggregates (EMCA) confined to gastrointestinal (GI) only with mild or no symptoms. Here we present a case with extensive atypical mast cell aggregates in lower GI tract yet no evidence of involvement of other organs.
Methods/Case Report
A 34-year-old woman presented with abdominal bloating, diarrhea along with pruritis but no cutaneous lesion. Biopsies from the ascending and descending colons, caecum and rectum consistently showed increased eosinophils and multifocal infiltrates of atypical spindle shaped mast cells which are positive for CD117/tryptase but negative for CD2 and CD25. This is consistent with SM by WHO criteria based on morphology. Bone marrow biopsy showed normal amount of mast cells with normal morphology. Upper gastrointestinal biopsy was unremarkable. Serum tryptase level was normal. No KIT mutation was detected in exon 9, 11, 13 or 17 from colonic mucosa. Patient has been treated with antihistamine and Montelukast and symptoms resolved.
Results (if a Case Study enter NA)
N/A
Conclusion
This case met the criteria of SM based on the presence of multifocal mast cell aggregates and atypical spindle morphology >25%. Johncilla et al. previously reported 16 cases of EMCA with atypical morphology or immunohistochemistry, absent to mild localized symptoms, and negative KIT mutation. Based on lack of generalized disease, the authors preferred using descriptive terminology instead of ‘systemic mastocytosis’ for those cases. Our case has broader involvement of lower gastrointestinal tract than any reported case and the patient needs treatment for the symptoms. However, there is no ‘systemic’ involvement of bone marrow or any other organ. The diagnosis of ‘Systemic Mastocytosis’ would cause potential confusion and/or unnecessary anxiety. Further study of more cases is needed to better characterize and categorize the cases of atypical mast cell aggregates localized only to the GI.
Indolent systemic mastocytosis or just ‘atypical enterocolic mast cell aggregates’?
