Her hemolysis continued, and on hospital day 15 a peripheral blood smear was significant for ring-formed parasites in red blood cells suggestive of babesiosis. became pancytopenic with an inappropriately low reticulocyte response (reticulocyte count, 1.6). A disseminated intra-vascular coagulation panel suggested hemolysis. A bone marrow biopsy specimen revealed patchy hypercellularity. Her hemolysis continued, and on hospital day 15 a peripheral blood smear was significant for ring-formed parasites in red blood cells suggestive of babesiosis. Further history elicited included a weekend at Montauk, NY, where tickborne diseases are prevalent, and she was subsequently prescribed azithromycin, atovaquone, and doxycycline. She was discharged on hospital day 25 and completed a 14-day course of antibiotics with complete recovery. Case 2 An 89-year-old white man was found to have a thymoma in 2002. He had a chronic cough with large amounts of white to green sputum and was being treated with nebulizers of albuterol and ipratropium bromide. His medical history included multiple pneumonias, bronchitis, deep venous thrombosis in the lower extremity, peripheral vascular disease, type 2 diabetes mellitus, multiple skin infections, and a blistering lesion on his leg for a number of years. He had been colonized by and was intermittently prescribed antibiotics. In November 2002, laboratory tests revealed the following: IgG, 198 mg/dL; IgA, 466 mg/dL; and IgM, less than 4 mg/dL. Flow cytometry revealed TH1338 virtually undetectable levels of peripheral B cells, normal levels of T cells and CD8 cells, but slightly reduced CD4 cells. Good syndrome was diagnosed, and he was given monthly IVIG at 400 mg/kg. His thymoma appeared to be stable on computed tomography. In July 2005, he underwent a biopsy of the left foot lesion, which was thought to TH1338 be chronic stasis dermatitis. He had multiple purplish raised nodules on both feet and along the medial anterior thigh in a linear pattern. Pathologic tests demonstrated a focus of superficial atypical vascular proliferation, which was positive for immunohistochemical staining by human herpesvirus 8 (HHV-8), consistent with Kaposi sarcoma. DISCUSSION Definition The association between the presence of a thymoma and adult-onset hypogammaglobulinemia was first described by Dr Robert Good in 1955.2 There are a number of definitions for Good syndrome. Practice parameters in 20053 define it as a subset of common variable immunodeficiency; however, the reduced numbers of peripheral B cells noted in Good syndrome are not a feature of common variable immunodeficiency, which typically shows impaired B-cell maturation. Others choose to define it as hypogammaglobulinemia with thymoma consistent with Dr Goods case. Our rationale for choosing to define Good syndrome as immunodeficiency with thymoma, a broader classification, is because the pathogenesis of the disease MYO7A remains unknown and patients have several other immunological impairments in addition to hypogammaglobulinemia (Table 1). Table 1 Important Features of Good Syndrome 2000;114: 760 C766. Pathogenesis The pathogenesis of Good syndrome is unknown; however, there are at least 3 suggested hypotheses. The first explanation derived from murine models demonstrates that cytokines such as limitin, an interferon-like cytokine produced by a bone marrow stromal cell line, influence B-cell precursor growth and differentiation, causing either cell arrest or impaired maturation.11 Second, many patients with Good syndrome experience opportunistic infections associated with defects in cell-mediated immunity, suggesting loss in either the na?ve or memory CD4+ T-cell population.12 Third, studies of paraneoplastic phenomena in thymoma, such as pure red cell aplasia, show that T cells or autoantibodies can directly or indirectly inhibit erythropoiesis, suggesting that loss of B-cell function could be due to autoimmune destruction.13 Immunological Investigation The immunologic hallmarks TH1338 include few to absent levels of B peripheral cells, hypogammaglobulinemia, CD4+ T lymphopenia, and impaired T-cell response. Immunophenotyping is essential in detecting and monitoring immunodeficiency in patients with a thymoma, since treatment with IVIG may potentially replace the defective antibody production.14 IgG antibodies to toxoplasmosis and cytomegalovirus should be determined to evaluate whether a patient is at risk of reactivated infections. If immunologic test results are normal, testing should be performed periodically if the clinical suspicion of Good syndrome persists, because there can be an interval between the diagnosis of immunodeficiency and/or thymoma and development of infection.15 Infectious Complications The initial clinical features of Good syndrome are varied. As reviewed by Tarr et al,1 in 51 patients, Good syndrome affects male and female patients equally. Most patients experienced infectious complications such as recurrent sinopulmonary infections secondary to encapsulated organisms (spp, in the United States or in Europe. have animal reservoirs such as rodents or cattle, but the disease is transmitted to humans via the ixodid tick. Definitive diagnosis is made by examination of the peripheral blood.