Stem cell self-renewal is regulated by intrinsic mechanisms and extrinsic signals mediated via specialized microenvironments called “niches.” The best-characterized stem cell is the hematopoietic stem cell (HSC). Self-renewal and differentiation ability of HSC are regulated by two major elements: endosteal and vascular regulatory elements. The osteoblastic niche localized at the inner surface of the bone cavity might serve as a reservoir for long-term HSC storage in a quiescent state. Whereas the vascular niche, which consists of sinusoidal endothelial cell lining blood vessel, provides an environment for short-term HSC proliferation and differentiation. Both niches act together to maintain hematopoietic homeostasis. In this paper, we provide some principles applying to the hematopoietic niches, which will be useful in the study and understanding of other stem cell niches. We will discuss altered microenvironment signaling leading to myeloid lineage disease. And finally, we will review some data on the development of acute myeloid leukemia from a subpopulation called leukemia-initiating cells (LIC), and we will discuss on the emerging evidences supporting the influence of the microenvironment on chemotherapy resistance.

Introduction Ibrutinib is an oral inhibitor of Bruton’s tyrosine kinase that is used for a variety of B cell hematological malignancies. Skin and subcutaneous tissue manifestations have been reported and were witnessed in up to 32% of the patients on ibrutinib. The mechanism in which ibrutinib can cause skin toxicities has been thought due to the inhibition of epidermal growth factor; c-Kit and platelet-derived growth factor receptor). Here, we report a case of an elderly chronic lymphocytic leukemia patient who developed multiple inflamed lesions and lower limb cellulitis in 100 days after initiating ibrutinib therapy. Case report A 68-year-old male patient with relapsed chronic lymphocytic leukemia was started on ibrutinib 420 mg orally daily following multiple lines of therapy. Three months following ibrutinib, the patient developed multiple hyper pigmented lesions over both forearms then over both thighs; buttocks and lower limbs. The lesions were labeled as ecthyma and cellulitis that started as papules, which progressed to pustules. Management and outcomes The patient required admission in which he received prolonged course of antibiotics. Biopsy from the wound showed soft tissue fragment infiltrated by acute and chronic inflammatory cells with necrosis; rare foreign body giant cells and granulation tissue formation; suggestive of abscess. Subsequently, ibrutinib was stopped permanently. Discussion This is the first case description of an ibrutinib-associated sever skin toxicity in Qatar. The provided information regarding the clinical descriptions of toxicity profiles in general and skin-based in particular is valuable information for daily clinical practice, especially when selecting the optimum first-line treatment for the patient.

Thalassemia syndrome has diverse clinical presentations and a global spread that has far exceeded the classical Mediterranean basin where the mutations arose. The mutations that give rise to either alpha or beta thalassemia are numerous, resulting in a wide spectrum of clinical severity ranging from carrier state to life-threatening, inherited hemolytic anemia that requires regular blood transfusion. Beta thalassemia major constitutes a remarkable challenge to health care providers. The complications arising due to the anemia, transfusional iron overload, as well as other therapy-related complications add to the complexity of this condition. To produce this consensus opinion manuscript, a PubMed search was performed to gather evidence-based original articles, review articles, as well as published work reflecting the experience of physicians and scientists in the Arabian Gulf region in an effort to standardize the management protocol.

Strongyloides stercoralis (S.S.) is a human intestinal parasite, which may lead to complicated strongyloidiasis. We report a case of disseminated strongyloidiasis following the treatment of myeloma. The patient developed skin lesions, respiratory distress, aseptic meningitis and bacterial and fungal sepsis. The diagnosis of strongyloidiasis was established through endotracheal tube secretions. Despite the treatment with Ivermectin and Albendazole, the outcome was fatal. The value of screening for strongyloidiasis is unclear but may be of benefit in patients with hematological malignancies from high endemic areas.

We declare no confl ict of interest. ABSTRACTStrongyloides stercoralis (S.S.) is a human intestinal parasite, which may lead to complicated strongyloidiasis. We report a case of disseminated strongyloidiasis following the treatment of myeloma. The patient developed skin lesions, respiratory distress, aseptic meningitis and bacterial and fungal sepsis. The diagnosis of strongyloidiasis was established through endotracheal tube secretions. Despite the treatment with Ivermectin and Albendazole, the outcome was fatal. The value of screening for strongyloidiasis is unclear but may be of benefi t in patients with hematological malignancies from high endemic areas.

Hematopoietic stem cell transplantation (HSCT) offers potentially curative therapy for many hematologic and nonhematologic conditions. As a successful outcome of Qatar's National Cancer Strategy, the HSCT program was started in the National Center for Cancer Care and Research (NCCCR) in October 2015. The HSCT program in NCCCR is the only transplant program in Qatar and self-sufficient with all three core components: the stem cell collection facility, the stem cell processing facility, and the clinical program, which are locally available at Hamad Medical Corporation. In this paper, we report on the outcomes of the first 16 patients who underwent autologous stem cell transplantations (ASCTs) in our center. A total of 17 ASCT have been performed for 16 adult (≥14years) patients. Thirteen of the 16 patients were eligible for disease evaluation at Day 100 post-ASCT. Among these patients, the overall response rate on Day 100 was 92% (complete remission, 61%; very good partial remission/partial remission, 31%) and stable disease occurred in 6%. The procedure was very well tolerated by all patients. At the time of writing this report, all patients are alive; however, one patient (6%) had disease relapse. The Day 100 post-ASCT nonrelapse mortality rate was 0%. Launching the HSCT program represents a historic milestone in the development of the health-care sector in Qatar. The 1st year of this program was very fruitful with the accomplishment of 17 successful transplants. We are in the process of starting the allogenic HSCT early next year. This would represent the next significant milestone for cancer care in Qatar.

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