Stem cell biology and regenerative medicine is a relatively young field. However, in recent years there has been a tremendous interest in stem cells possibly due to their therapeutic potential in disease states. As a classical definition, a stem cell is an undifferentiated cell that can produce daughter cells that can either remain a stem cell in a process called self-renew¬al, or commit to a specific cell type via the initiation of a differentiation pathway leading to the production of mature progeny cells. Despite this acknowledged definition, the classification of stem cells has been a perplexing notion that may often raise misconception even among stem cell biologists. Therefore, the aim of this brief review is to give a conceptual approach to classifying the stem cells beginning from the early morula stage totipotent embryonic stem cells to the unipotent tissue-resident adult stem cells, also called tissue-specific stem cells.

Multiple myeloma has been recognized since at least the middle of the 19 th century. The list of therapies used in the treat¬ment of myeloma is long but only recently has therapeutic success approached a level commensurate with disease con¬trol, although cure remains elusive. The complexity of the disease, invidual variations and very active ongoing clinical research warrants continous updating of current information. This review not only summarizes the level of success that has been achieved during the past years but also points to the drawbacks in the current treatment strategies giving emphasize to the potential solutions in the future.

OBJECTIVE: The aim of this study was to determine the incidence of pancytopenia in relation to sex and age and to become aware of the clinical manifestations of pancytopenic patients according to the causes of pancytopenia. MATERIALS-METHODS: This was a prospective descriptive study that included all patients with pancytopenia admitted to or attending the Hematology-Oncology Department in Al-Gamhouria Teaching Hospital, Aden, during the period 1 January–31 December 2005. RESULTS: The most common causes of pancytopenia were malaria and hypersplenism in > 45% of patients, followed by megaloblastic anemia in 14.7%, and aplastic anemia and acute leukemia in 13.3% each. The other causes as determined in the present study were myelodysplasia in 8.0%, myelofibrosis in 4.0% and iron deficiency anemia in 1.3%. The most common symptom was fever in 86.7% of patients. Pallor and splenomegaly were the most common physical findings. CONCLUSIONS: Hypersplenism and malaria were the most common causes of pancytopenia followed by megaloblastic anemia, aplastic anemia and acute leukemia.

Lymphoma is the second most common neoplasm of the head and neck after squamous carcinoma. The majority of lym¬phomas involving the head and neck are non-hodgkin’s lymphomas. Hodgkin’s lymphoma is rare in Waldeyer’s ring. Between 1999 and 2006, the medical records and pathology data of all newly diagnosed, previously untreated adult patients with Waldeyer’s ring lymphomas were retrospectively reviewed. Pathologic specimens were adopted according to WHO his¬tologic classification. All patients were clinically staged with history and physical examination, routine hematologic and bio¬chemical profiles, chest X-ray, and computerized tomography of the head and neck, chest, abdomen and pelvis. All patients were treated with chemotherapy. Approximately one month after the end of the scheduled initial management, patients were restaged for evidence of residual disease with physical examination, laboratory profiles and relevant radiologic studies. Total patient number was 11 in our institution. Complete remission was achieved in 6 patients and partial remission in 3 patients; 1 patient did not achieve remission and 1 patient with anaplastic large cell lymphoma died. Patients who are alive are still being followed in our institution. The progression of patients with lymphoma is closely associated with the diagnosis, stage and histologic grade of the disease. This series characterized the clinicopathologic features and outcomes of adult patients. Our data have shown that there is relatively good survival in these diseases but more patients must be evaluated for mean¬ingful results.

AMAÇ: Bu çalışmanın amacı 7-14 yaşlarında talasemi major tanısı alan 23 hastanın kemik mineral dansitesini ve iki yıllık takip sonrası kemik dansitesindeki değişiklikleri (KMD) değerlendirmektir. YÖNTEM: Lumber vertebra ve femoral boyun Dual enerji X-ray absorbsiyometri (DXA) ile başlangıçta, tedaviden 12 ay ve 2 yıl sonra değerlendirildi. Pamidronat tedavisi (15mg/doz, bir yıl süreyle 3 ayda bir) 23 osteoporotik (Z skoru -2,5 altında) ve osteopenik (Z skoru -1 ile -2,5 arası) hastaya verildi. Tedaviden 12 ay sonra tüm hastalara sadece kalsiyum ve vitamin D verildi. İki yıl sonra lumber vertebra ve femur KMD’si DXA ile ölçüldü. BULGULAR: Pamidronat verilmesi femur boyun KMD’sinde önemli bir artış sağladı. Lumber vertebra KMD’si pamidronat grubunda başlangıç grubuna göre hafif yüksekti ama bu istatistiksel olarak anlamlı değildi. İki yıl sonra femur boynu ve lum¬ber vertebra KMD’sinde artış vardı. SONUÇ: Bu bulgular doğrultusunda, uzun dönem tedaviyi belirlemek için daha uzun dönem takip çalışmalarına ihtiyaç vardır.

INTRODUCTION: Aspirin has been shown to have variable antiplatelet activity in individuals. Previous studies have estimated that 5% to 45% of the population do not achieve an adequate antiplatelet effect from aspirin and still suffer ischemic events despite therapy. AIM: In this study, we aimed to evaluate aspirin resistance in healthy males. METHOD: We prospectively enrolled 175 healthy males who were ≥19 years old and taking 100 mg of aspirin daily ≥7 consec¬utive days before study entry. Demographic information and laboratory data were collected. Aspirin resistance was detected by optical platelet aggregometry, a widely accepted method using adenosine diphosphate (ADP) and arachidonic acid (AA). RESULT: 28% of the participants were aspirin-resistant, 62% were aspirin-semi-responders and 10% were aspirin-sensitive. The aspirin-resistant individuals were older than the semi-responders (p<0.01), and had higher erythrocyte sedimentation rate than the semi-responders (p<0.01) and sensitive individuals (p<0.05). CONCLUSION: Our study demonstrates aspirin resistance to be particularly important given its high frequency in our study population. The biological effects of aspirin, which is widely used as an antithrombotic drug, are not similar in all individuals.

OBJECTIVE: We retrospectively analyzed the impact of pre- and post-transplant variables on the outcome of transplanta¬tion in 145 consecutive patients with acute myeloblastic leukemia (AML) allografted from their HLA-identical siblings in our single center cohort. RESULTS: The stem cell source used was bone marrow (BM) (36.6%) or peripheral blood (PB) (63.4%). Both neutrophil and platelet engraftments were observed on the median 14th day. Engraftment was faster in the PB group than in the BM group (p<0.0001). Severe acute graft versus host disease (aGvHD) was observed in 27.9% of the patients while chronic (c)GvHD developed in 61.2%. The use of PB was associated with more severe aGvHD. Estimated leukemia-free survival (LFS) and overall survival (OS) at 10 years were 43.4%±5.2% and 52.7%±4.6%, respectively. CONCLUSION: Both in univariate and multivariate analyses for LFS and OS, remission status at transplant and the presence of aGvHD were independent risk factors.

Aplastic anemia (AA) may evolve into clonal diseases like myelodysplastic syndrome (MDS) and acute myeloblastic leuke¬mia (AML). Monosomy 7 is a poor prognostic chromosomal abnormality commonly associated with therapy related MDS and secondary AML. It has also been associated with leukomogenic transformation in AA. We present here two adult ma¬le patients with acquired severe AA. Both patients had received immunosuppressive therapy (IST) as first line treatment and had monosomy 7 positive clone at transformation to MDS with refractory anemia and excess of blast (RAEB-II) and AML, respectively. Both patients have undergone allogeneic hematopoietic stem cell (HSC) transplantation from their HLA identical donors (unrelated and sibling).

Extramedullary leukaemic involvement is not uncommon as part of the presentation in acute myeloid leukaemia (AML). However, infiltrative peripheral neuropathy due to AML was rarely reported. We report a case of extramedullary leukaemic infiltration of the brachial plexus in a patient with relapsed AML.

Diffuse alveolar hemorrhage, with a mortality rate between 60-100%, is a life-threatening complication in hematopoietic stem cell transplant recipients. A 34-year-old man, with precursor B acute lymphoblastic leukemia diagnosed in July 2003, relapsed after allogeneic peripheral blood hematopoietic stem cell transplantation from his human leukocyte antigen- iden¬tical brother in July 2005. He received a donor lymphocyte infusion of 2 x 107/kg CD3 positive cells. He developed fever, dyspnea and hypoxemia four days after donor lymphocyte infusion. The patient was diagnosed as diffuse alveolar hem¬orrhage based on the clinical, radiological and bronchoscopic data. He was immediately started on high-dose methylpred¬nisolone. Two days after the onset of the steroid therapy, he recovered with significant improvement in oxygenation. Diffuse alveolar hemorrhage can be a late-onset transplant complication that could also be associated with a recent donor lymphocyte infusion.