Impaired function of macrophage Fc gamma receptors in end-stage renal disease

Article Abstract:

Patients with severely impaired kidney function as a result of the final stages of kidney disease often undergo hemodialysis, a procedure whereby the patient's blood is shunted from the body, cleansed of impurities in a machine, and returned to the body. A common complication of hemodialysis is a high infection rate, the primary cause of death among these patients. The reason for this high rate is not known, but it is likely that the patients' immune systems are not functioning adequately. A type of white blood cell normally active in the immune response, the macrophage, was studied in 56 dialysis patients and 20 healthy control subjects. One way macrophages fight invading microorganisms such as bacteria is by engulfing and eliminating them after the bacteria have been coated with antibodies. Macrophages can do this because they possess molecules on their surfaces (Fc receptors) that can recognize and bind to the tail regions (Fc region) of antibodies. The competence of the patients' macrophages was tested in two ways: by measuring the cells' ability to remove antibody-coated red blood cells that had been injected into the patients' bloodstream (clearance test), and by measuring their ability to bind to these same cells under laboratory conditions. In the patients, one type of Fc receptor (the Fc-gamma receptor, which binds to antibodies of the IgG-class) was clearly impaired in both test conditions as compared with the control group. Macrophage binding to antibody-coated red blood cells under laboratory conditions showed partial improvement after hemodialysis. Nine of the 56 patients experienced severe infections during the two-year follow-up period. This subgroup had even greater impairment of Fc-receptor function in the clearance studies than that shown by the remaining 47 patients. It is likely that this abnormality in Fc receptor function among patients with end-stage renal disease undergoing dialysis contributes to their high rate of infection. (Consumer Summary produced by Reliance Medical Information, Inc.)

Research, Physiological aspects, Macrophages, Kidney diseases, Fc receptors

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Erythropoietin for the treatment of porphyria cutanea tarda in a patient on long-term hemodialysis

Article Abstract:

Porphyria cutanea tarda is a metabolic condition which is caused by the deficiency of a liver enzyme (uroporphyrinogen decarboxylase). As a result of this deficiency the iron content of the liver becomes elevated and leads to cutaneous photosensitivity, the production of a skin rash and skin lesions with exposure to light. One form of treatment is bleeding the individual (phlebotomy) to deplete the accumulated iron and induce the production of new liver enzymes. Some patients who are placed on kidney hemodialysis develop porphyria cutanea tarda because iron-containing molecules are not removed by the blood-filtering process of the artificial kidney machine. As a result the blood levels of porphyrins become elevated and cause a cutaneous photosensitivity which is more severe than that seen in porphyria cutanea tarda. Dialysis patients often suffer from anemia (too few iron-containing red blood cells), and bleeding is not an option for them. A recent development in genetic engineering has been the synthesis of a normal hormone, erythropoietin, which stimulates the bone marrow to produce red blood cells. The current report explores the use of pharmacologic administration of erythropoietin to a 57-year-old hemodialysis patient who developed cutaneous photosensitivity. The increased level of red blood cell production in this patient allowed bleeding to be performed and consequently reduced the severe ulcerating and infected skin wounds on her hands, forearms and face. The treatment course of this dialysis patient was markedly improved by erythropoietin treatment which can be combined with bleeding. (Consumer Summary produced by Reliance Medical Information, Inc.)

Care and treatment, Skin diseases, Erythropoietin

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Porphyria cutanea tarda and haemochromatosis: a family study

Article Abstract:

Porphyria is a group of disorders in which there is increased formation and excretion of porphyrins (precursors of hemoglobin, the oxygen-carrying blood protein). Hemochromatosis is a disease involving a defect in iron metabolism in which iron accumulates in body tissues. Both porphyria cutanea tarda and hemochromatosis are inherited disorders. A case is reported of a 73-year-old woman who was admitted to the hospital following lack of appetite, malaise, and increased pigmentation on light-exposed areas of the skin; these symptoms had persisted for three months. Results from laboratory tests and a diagnosis of diabetes mellitus suggested that the patient had hemochromatosis; screening for porphyria was negative. Screening of other family members indicated that a niece had similar laboratory results, along with a medical condition that was probably related to hemochromatosis. The patient was then treated by venesection, removal of blood, and improved after only two units were removed. This was unusual, as patients with hemochromatosis usually require 20 to 30 venesections before iron status normalizes. Rescreening for porphyria, which was more in keeping with her response to treatment, was performed. Further tests showed that the woman had sporadic porphyria cutanea tarda that was probably provoked by excessive iron absorption caused by the hemochromatosis gene. This case study emphasizes that porphyria should be suspected in cases of pigmentation, and full urine and fecal testing is needed before it is ruled out as a cause of iron overload. (Consumer Summary produced by Reliance Medical Information, Inc.)

Diagnosis, Hemochromatosis

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