a rare case of adult hairy cell leukemia ( hcl ) with duodenal involvement is presented . the patient was a 48-year - old man , who had a history of hairy cell leukemia . three days after completion of 2-chlorodeoxyadenosine ( cda ) chemotherapy , the patient started experiencing abdominal pain . an extensive gastroenterological workup culminated in the patient getting an esophagogastroduodenoscopy ( egd ) that revealed duodenal inflammation and biopsies were taken . the duodenal biopsy was positive for chronic inflammatory infiltrate , primarily consisting of atypical lymphocytes and plasma cells with tartrate - resistant acid phosphatase ( trap ) positivity , and hence a diagnosis of duodenal involvement with hcl was made . repeat bone marrow biopsy done 2 weeks after finishing chemotherapy revealed residual disease . at the 3-month follow - up , the patient was asymptomatic with a normocellular marrow and no residual disease . repeat abdomen computerized tomography ( ct ) scan at completion of therapy showed resolution of duodenal thickening and spleen size of 12 cm . currently , patient is in clinical remission for 6 years with 4 - 6 monthly follow - up visits and continues to do well . this case is presented to highlight the first case report of hcl with duodenal involvement that was successfully treated with cda . hairy cell leukemia ( hcl ) is a chronic b - cell lymphoproliferative disorder that obtains its name from the fine hair - like projections seen on the cell surfaces under microscopy . clinically , hcl is associated with splenomegaly and pancytopenia while the cells infiltrate the bone marrow , liver , and spleen . however , unlike most mature b - cell lymphomas , hcl shows minimal lymph node involvement and absence of chromosomal translocations . the nature of its spread is attributed to its unique homing properties being limited to the blood compartments . a 48-year - old hispanic male presented to the emergency room ( er ) with colitis in march 2008 . hematological workup revealed pancytopenia ( hemoglobin , 6.9 gm ; leukocyte count , 4800/ul ; platelet count , 23,000/ul ) . computerized tomography ( ct ) scan abdomen revealed a massive splenomegaly ( 17 cm ) . bone marrow aspiration and biopsy showed hypercellular marrow diffusely infiltrated by small lymphocytes with round to bean shaped nuclei with reticulated chromatin pattern and abundant cytoplasm . immunohistochemical staining showed monoclonal kappa expressing b cell population positive for cd19 , cd22 , and cd45 and trap [ figure 1 ] while negative for cd23 , cd10 , cd5 , and cd3 . reticulin stain showed diffuse increase in reticulin fibers in the marrow . a subsequent diagnosis of hcl was made and the patient received outpatient 2-chlorodeoxyadenosine ( cda ) 0.1 mg / kg for 5 days . he was readmitted 3 days after completion of chemotherapy with febrile neutropenia , severe abdominal pain , and skin rash . the duodenal biopsy was positive for chronic inflammatory infiltrate , primarily consisting of atypical lymphocytes and plasma cells with trap positivity and hence a diagnosis of duodenal involvement with hcl was made [ figure 2 ] . repeat bone marrow biopsy done 2 weeks after finishing chemotherapy revealed residual disease . at the 3-month follow - up , the patient was asymptomatic with a normocellular marrow and no residual disease . labs showed a leukocyte count of 2800/ul , hemoglobin at 10 gm% , and platelet count of 246,000/ul . repeat abdomen ct scan in march 2009 showed resolution of duodenal thickening and spleen size of 12 cm . currently , the patient has been in clinical remission for 6 years with 4 - 6 monthly follow up visits and continues to do well . bone marrow biopsy demonstrates numerous hairy cells admixed with other elements trap stain of hcl showing bright granular cytoplasmic positivity in the leukemic cells infiltrating the duodenum hcl is rare b - cell lymphoproliferative disorder with annual incidence of 3 cases per million populations . hcl is predominately seen in males and caucasians with a median age of presentation being 52 years . the world health organization ( who ) classifies hcl as mature b - cell neoplasm with predilection for splenic involvement and certain immunophenotypic characteristics . classically , diagnosis of hcl was confirmed by trap activity , although the standard practice today is immunophenotyping by flow cytometry where hcl is characterized by the expression of b - cell antigens cd19 , cd20 , and cd22 in addition to coexpression of the surface antigens cd11c , cd25 , and cd103 . the classical cytologic features of the hcl include mature lymphocyte of a small size and round nuclear contour with a condensed chromatin and indistinct nucleolus , abundant pale cytoplasm , and circumferential cytoplasmic projections . the finding of hairy cells having nuclei widely separated by abundant cytoplasm , resulting in the so - called  fried - egg  appearance , can sometimes help to confirm the diagnosis . clinically , these patients present with splenomegaly , pancytopenia , and the bone marrow is usually involved in all patients with hcl . typical sites that are involved by hcl are the bone marrow and splenic red pulp ; the disease can also be more widespread and involve extramedullary sites such as the central nervous system , gastrointestinal and urogenital tracts , heart , lungs , skeletal muscle , skin , thymus , and thyroid . involvement of the bone marrow in hcl with associated reticulin fibrosis results characteristically in hypocellular aspirate smears or dry tap . our patient presented with residual bone marrow disease at the time of diagnosis of duodenal hcl . this , to our knowledge , is the first case report of hcl manifesting clinically with duodenal involvement .
context : a rare case of adult hairy cell leukemia ( hcl ) with duodenal involvement is presented.case report : the patient was a 48-year - old man , who had a history of hairy cell leukemia . 
 three days after completion of 2-chlorodeoxyadenosine ( cda ) chemotherapy , the patient started experiencing abdominal pain . 
 an extensive gastroenterological workup culminated in the patient getting an esophagogastroduodenoscopy ( egd ) that revealed duodenal inflammation and biopsies were taken . 
 the duodenal biopsy was positive for chronic inflammatory infiltrate , primarily consisting of atypical lymphocytes and plasma cells with tartrate - resistant acid phosphatase ( trap ) positivity , and hence a diagnosis of duodenal involvement with hcl was made . 
 repeat bone marrow biopsy done 2 weeks after finishing chemotherapy revealed residual disease . at the 3-month follow - up , 
 the patient was asymptomatic with a normocellular marrow and no residual disease . 
 repeat abdomen computerized tomography ( ct ) scan at completion of therapy showed resolution of duodenal thickening and spleen size of 12 cm . 
 currently , patient is in clinical remission for 6 years with 4 - 6 monthly follow - up visits and continues to do well.conclusion:this case is presented to highlight the first case report of hcl with duodenal involvement that was successfully treated with cda .