Dyserythropoiesis in homozygous haemoglobin C disease

Electron microscope studies of the bone marrow of three patients with homozygous haemoglobin C (HbC) disease have shown marked ultrastructural abnormalities in several of the polychromatic erythroblasts and marrow reticulocytes and the presence of phagocytosed erythroblasts within the macrophages. Such abnormalities were not found in the bone marrow of three patients with sickle cell anaemia indicating that the abnormalities represented a feature of HbC disease rather than a disturbance secondary to peripheral haemolysis. The characteristic ultrastructural finding in the polychromatic erythroblasts in HbC disease was the presence of grossly-disorganized nuclei showing multiple intranuclear clefts, the loss of parts of the nuclear membrane, oozing of nuclear material into the cytoplasm and an alteration of the structure and stainability of the nuclear chromatin. It is proposed that both the dyserythropoiesis and ineffective erythropoiesis in HbC disease may have resulted from the formation in vivo of very small aggregates of HbC within erythropoietic cells.

Ultrastructural abnormalities and arrest of protein biosynthesis in some erythroblasts from homozygotes for haemoglobin C and double heterozygotes for haemoglobin C and beta-thalassaemia

Various ultrastructural abnormalities were found in the erythroblasts of three homozygotes for haemoglobin C (HbC), one patient with HbC/beta(+)-thalassaemia and one patient with HbC/beta (0) thalassaemia. These included a coarsely granular or reticular appearance and altered electron-density of the heterochromatin, loss of parts of the nuclear membrane, and oozing of nuclear material into the cytoplasm. In addition, the two patients with HbC/beta-thalassaemia, but not the others, showed precipitated intracytoplasmic alpha-chains in a few profiles of polychromatic erythroblasts and marrow reticulocytes. Electron microscope autoradiographic studies of bone marrow cells from two of the patients with HbC disease and the patient with HbC/beta (0)-thalassaemia showed a marked depression or failure of incorporation of 3H-leucine into protein in some of the ultrastructurally abnormal erythroblasts. This impairment of protein synthesis may lead to alterations in the erythroblast membrane that are involved in the recognition and phagocytosis of the abnormal erythroblasts by macrophages.

Blood Transfusions Leading to Apparent Hemoglobin C, S, and O-Arab Hemoglobinopathies

Context.—Apparent hemoglobinopathies caused by blood transfusions rarely have been reported in the scientific literature.

Objective.—To interpret the abnormal hemoglobins appearing as small peaks on hemoglobin chromatograms or electrophoresis membranes.

Design.—In the clinical laboratories of a university hospital and a metropolitan hospital affiliated with a medical school, we interpreted hemoglobin chromatograms and electrophoresis membranes; correlated them with patients' medical, laboratory, and transfusion records; and when possible, identified the abnormal hemoglobin in the donors' transfusion segments.

Results.—We detected 52 incidences of apparent hemoglobinopathies in 32 recipients caused by blood transfusion, of which 46 were hemoglobin C, 4 were hemoglobin S, and 2 were hemoglobin O-Arab. When first detected, the abnormal hemoglobins in recipients ranged from 0.8% to 14% (median, 5.6%). Multiple transfusions with abnormal hemoglobins occurred in 11 patients with 2 patients receiving hemoglobin C blood 5 separate times. One patient received hemoglobin C and later S, and another patient received C and later O-Arab.

Conclusions.—Apparent hemoglobinopathies caused by blood transfusions are far more common than previously reported and represent diagnostic challenges. Misdiagnosis could lead to unnecessary testing, treatment, and counseling. If a hemoglobinopathy from a unit of transfused blood is identified in a recipient, we recommend notifying the donor of that abnormality.

Intrathoracic extramedullary hematopoietic tumor in hemoglobin C disease

A case of intrathoracic extramedullary hematopoietic tumor associated with hemoglobin C disease is reported in a 27-year-old Bangladeshi man. The patient's initial complaints were generalized weakness, weight loss, and left upper abdominal pain. Hospital workup revealed a solitary intrathoracic mass in the posterior mediastinum, which was suspected to be a lymphoma based on fine-needle aspiration. The mass was excised and proved to be an extramedullary hematopoietic tumor. The problem of differential diagnosis is discussed.

Retinal and choroidal neovascularization in sickle cell disease

Small vessel obstruction characterizes sickle cell disease and, when occurring in the peripheral retinal vessels, initiates a sequence of vascular events which may culminate in the development of proliferative sickle retinopathy (PSR). Repeated examinations of the retinal vasculature of patients with different genotypes of sickle cell disease over the last 10 years (Condon and Serjeant, 1972a, b, c; 1975; 1980a) have allowed observations on the natural history of PSR and on factors related to its development. Choroidal neovascularization has been a common complication of a trial of xenon arc photo-coagulation in PSR. Observations on the aetiology and natural history of both retinal and choroidal neovascularization are presented in this report.

Fluorescein angiography in sickle-cell retinopathy and von Hippel-Lindau disease

Fundus involvement in sickle-cell-hemoglobin C disease and von Hippel-Lindau disease was ascertained by clinical observation with the benefit of indirect ophthalmoscopy. Fluorescein angiography, however, has added new dimensions to our understanding of early lesions in these entities, the morphology of full-blown lesions, and the evaluation of therapeutic efforts to obliterate them. Like so many adjunct studies available to us today in medicine, it does not replace clinical acumen, but enhances evaluation.

Macular and perimacular vascular remodelling sickling haemoglobinopathies

The posterior pole vasculature of 100 patients with different sickling haemoglobinopathies was studied prospectively over a period of three years. Various abnormalities of the posterior pole vasculature were seen in 29 per cent of the patients. Continuous remodelling of the macular and perimacular vasculature occurred. Visual acuity was variably affected and sometimes remained intact.

Migratory white-without-pressure retinal lesions

Nine patients had white-without-pressure retinal lesions. These lesions were seen in areas of vitreoretinal adhesions. The configuration and location of these lesions changed over variable periods of time. The cause of this pecular migration is unknown, but may be related to separation and re-creation of vitreoretinal adhesions. The migratory nature of white-without-pressure areas has not, to our knowledge, previously been reported in the literature.

Spontaneous remodeling of the peripheral retinal vasculature in sickling disorders

Periodic photographic and angiographic surveys of patients with the earliest stages of sickle retinopathy showed a number of fundus findings. In seven cases (sickle cell anemia, four; sickle cell hemoglobin C, three), these findings included: (1) a variety of vascular abnormalities in the equatorial and post-equatorial retina such as segmented dilations of the vessel walls, hairpin-shaped vascular loops, hypertrophic, tortuous A-V anastomoses, intraluminal plugs, closure and loss of capillary bed, and terminal budding of capillaries; and (2) a continuous, spontaneous remodeling of the peripheral retinal vasculature due to successive closures and reopenings of equatorial retinal vessels. A centripetal recession of the peripheral retinal vasculature usually resulted. No correlation between the ophthalmoscopic and the systemic condition of the patients could be made.

Molecular mechanism of hemolytic anemia in homozygous hemoglobin C disease. Electron microscopic study by the freeze-etching technique

Erythrocytes from a patient with homozygous hemoglobin C disease were subjected to gradual osmotic dehydration by incubation in hypertonic saline. Serial observations of these cells before and after 4 and 12 hr incubation were carried out by means of interference, Soret absorption, polarization microscopy, and the electron microscope employing the freeze-etching technique. Light microscopic studies showed a progressive contraction of cellular contents into central masses which, after 12 hr dehydration, formed birefringent intracellular hemoglobin crystals in 50-75% of the cells. Electron microscopic study of freeze-etched replicas of these cells at 0, 4, and 12 hr of dehydration reveals progressive aggregation, alignment, and crystallization of hemoglobin molecules. Molecular aggregation found in C-C cells prior to osmotic dehydration was not seen in normal erythrocytes. Aggregation and packing varied from cell to cell. Reticulocytes showed a loosely packed aggregate mesh-work; older cells showed variation of molecular packing, which appeared tightest in cells corresponding to microspherocytes. With further loss of intracellular water, aggregates coalesced into patterns of tighter molecular packing with small regions of alignment, and, finally, crystallization occurred. Hemoglobin molecules measuring 70 A in diameter were readily identified within the period patterns of intracellular crystals. These findings suggest that the hemoglobin C molecules within C-C erythrocytes exist in an aggregated state. As the cell ages, intracellular water is lost and intermolecular distance decreases, hemoglobin C molecules polymerize into intracellular crystals. This pathological behavior of hemoglobin C is associated with a charge alteration conferred by the substitution of beta-6-lysine for glutamic acid on the external surface in the A-helix region of the beta-chain of the molecule, possibly increasing intermolecular attraction. Molecular aggregation accounts for the increased rigidity of C-C cells which leads to accelerated membrane and water loss with resultant microspherocyte formation. The microspherocyte, with highest intracellular hemoglobin concentration, rapidly undergoes intracellular crystallization, and is sequestered and destroyed by reticuloendothelial elements.