ZHIHONG HU, MD, PhD Fellow, Department of Hematopahtology The University of Texas MD Anderson Cancer center

CLINICAL HISTORY A 25-year-old man diagnosed with rheumatoid arthritis for the past 3 years On follow-up of a repeat CBC, significant leukocytosis with eosinophilia about 6 months Had an extensive workup done: negative for ova and parasites, strongyloids A bone marrow biopsy was completely negative, negative for BCR-ABL, JAK2 , PDGFR alpha and beta Echocardiogram was negative

CLINICAL HISTORY (cont’d) For his RA, treated with methotrexate Switched to leflunomide for the past month due to intolerance to methotrexate Not much complaints, except for two nodules on the right leg, and other symptoms secondary to RA (joint stiffness and swelling (small joints of his hands, elbows and wrists) in the morning that lasts more than 1 hour, which is consistent with his RA No good reason for his underlying eosinophilia other than his rheumatoid arthritis

ANCILLARY STUDIES CBC: WBC 38.2K/mL H (4.0-11.0) RBC 4.50M/mL (4.50-6.00) Hgb 13.9gm/dL L (14.0-18.0) Neutrophil: 22.0% L (42.0-66.0); 8.40K/mL H (1.70-7.30), Lymphocyte:15.0% L(24.0-44.0); 5.73K/mL H (1.00-4.80) Monocyte: 2.0% (2.0-7.0); 0.76K/mL H (0.08-0.70), Eosinophil: 61.0% H (1.0-4.0); 23.30K/mL H (0.04-0.40) Sodium 139, potassium 4.4, chloride 104, bicarb 28, BUN 7, creatinine 0.84, glucose 47

PERIPHERAL BLOOD SMEAR

BONE MARROW BIOPSY

PROPOSED DIAGNOSIS Cellular (80%) bone marrow with trilineage hematopoiesis and marked eosinophilia, compatible with LYMPHOCYTE VARIANT OF HYPEREOSINOPHILIC SYNDROME Sub-diagnostic systemic mastocytosis

TAKE HOME MASSAGE Aberrant T cell population of CD3-CD4+ immunophenotype is seen in the lymphoid variant of hypereosinophilic syndrome (L-HES) Monoclonal TCR gamma gene arrangement can be detected in L-HES Sub-diagnostic systemic mastocytosis: those meeting 1-2 minor criteria for SM only