1/22. A novel mutation in the NADH-cytochrome b5 reductase gene of a Chinese patient with recessive congenital methemoglobinemia.Recessive congenital methemoglobinemia due to nicotinamide adenine dinucleotide (NADH)-cytochrome b5 reductase (b5R) deficiency is classified into 2 clinical types: type 1 (erythrocyte type) and type 2 (generalized type). We found a Chinese family with type 1 recessive congenital methemoglobinemia, the patients from which were diagnosed according to clinical symptoms and b5R enzyme activity in the blood cells. To learn the molecular basis of type 1 recessive congenital methemoglobinemia in this Chinese family, we isolated total rna from the peripheral leukocytes of the propositus and b5R complementary dna (cDNA) by reverse transcription- polymerase chain reaction (RT-PCR). The coding region of the b5R cDNA was analyzed by sequencing the cloned PCR products. The results showed that the propositus was homozygous for a G-->A transition at codon 203 in exon 7, changing a cysteine to a tyrosine (Cys203Tyr). To characterize the mutant enzyme, both glutathione S-transferase (GST)-fused wild-type b5R and GST-fused mutant Cys203Tyr b5R were expressed in escherichia coli and affinity purified. The results showed that the catalytic activity of the enzyme was not much affected by this amino acid substitution, but the mutant enzyme exhibited decreased heat stability and increased susceptibility to trypsin. These properties of the mutant enzyme would account for the restricted b5R deficiency and mild clinical manifestations of these type 1 patients. The finding of this novel mutation makes codon 203 the only position within the b5R gene at which more than 1 mutation has been found.- - - - - - - - - - ranking = 1keywords = blood cell (Clic here for more details about this article) |
2/22. Haemolytic anaemia after oral self-giving of naphthalene-containing oil.A clinical case of suicide attempt by means of oral self-giving of naphthalene-containing oil in an old man was reported. Clinical features showed haemolytic anaemia supported by a decrease of haemoglobin concentration and red blood cell count, an increase of bilirubin (prevalently indirect) and lactate dehydrogenase and very low levels of haptoglobin. Methaemoglobin (metHb) measured at admission to the Emergency Room and 19 days after poisoning was still above normal limits. No deficiency of glucose-6-phosphate dehydrogenase was detected. The clinical manifestations ameliorated after treatment with concentrated red blood cells and ascorbic acid, with fast normalization of metHb. The clinical picture appeared almost normal 1 month after poisoning. The clinical diagnosis was 'haemolytic anaemia caused by naphthalene'. Absence of glucose-6-phosphate dehydrogenase deficiency probably reduced the severity of poisoning.- - - - - - - - - - ranking = 2keywords = blood cell (Clic here for more details about this article) |
3/22. methemoglobinemia following unintentional ingestion of sodium nitrite--new york, 2002.methemoglobinemia is an unusual and potentially fatal condition in which hemoglobin is oxidized to methemoglobin and loses its ability to bind and transport oxygen. The most common cause of methemoglobinemia is the ingestion or inhalation of oxidizing agents such as nitrates or nitrites (e.g., sodium nitrite, which is used commonly as a preservative in curing meats and fish). This report summarizes the investigation of an incident of methemoglobinemia in five members of a household in new york who became ill after eating a meal seasoned with a white crystalline substance from a plastic bag labeled "Refined Iodized Table Salt" (Figure). The findings underscore the need for proper storage of hazardous materials to avoid unintentional ingestion and the importance of collaboration by multiple agencies to address a potential public health emergency.- - - - - - - - - - ranking = 0.011920357043008keywords = white (Clic here for more details about this article) |
4/22. Congenital methemoglobinemia due to NADH-methemoglobin reductase deficiency in three Indian families.Congenital methemoglobinemia is a relatively rare clinical disorder characterized by life-long cyanosis, caused by either an inherited mutant hemoglobin (Hb-M) or deficiency of physiologically active NADH-dependent methemoglobin reductase (NADH-MR). NADH-MR deficiency leads to two different types of recessive congenital methemoglobinemia. In type I, cyanosis is the only major symptom and NADH-MR deficiency is restricted only to the red blood cells. In type II, cyanosis is associated with severe mental retardation and neurological impairment. The objective of this study is to establish the cause of cyanosis in our cases of congenital methaemoglobinemia. Erythrocyte NADH-MR activity was assayed spectrophotometrically. Spectral analysis of the hemolysate treated with potassium ferricyanide was recorded between 400-700 nm and Hb electrophoresis on starch gel at pH 7.0 was done to rule out the presence of Hb-M. NADH-MR deficiency was detected in 3 families. There was a history of consanguinity in one of these cases. The three propositi presented with breathlessness, fever and peripheral cyanosis. There was no history of cardiac illness or exposure to drugs and chemicals. There were no signs and symptoms of mental retardation. The presence of Hb-M was ruled out. Hb-A2, Hb-F, G6PD activity and reduced glutathione levels were normal. NADH-MR activity in all the cases ranged from 4.1 to 9.2 IU/g Hb (normal range 7.0-24.0 IU/g Hb). We describe NADH-MR deficiency in three unrelated cases (age 4 months to 6 years) where the activity of the enzyme was 30-40% of normal. These three cases of congenital methemoglobinemia are due to type-I NADH-MR deficiency without mental retardation.- - - - - - - - - - ranking = 1keywords = blood cell (Clic here for more details about this article) |
5/22. Congenital methemoglobinemia: a rare cause of cyanosis in the newborn--a case report.cyanosis is a physical finding that can occur at any age but presents the greatest challenge when it occurs in the newborn. The cause is multiple, and it usually represents an ominous sign, especially when it occurs in association with neonatal sepsis, cyanotic congenital heart disease, and airway abnormalities. cyanosis caused by abnormal forms of hemoglobin can also be life-threatening, and early recognition is mandatory to prevent unnecessary investigations and delay in management. Abnormal hemoglobin, such as hemoglobin m, is traditionally discovered by electrophoresis, so the newborn screen, which is mandatory in several states, is a useful tool for the diagnosis. Although acquired methemoglobinemia, caused by environmental oxidizing agents, is common, congenital deficiency of the innate reducing enzyme is so rare that only a few cases are documented in the medical literature around the world. We present a neonate with cyanosis as a result of congenital deficiency of the reduced nicotinamide adenine dinucleotide-cytochrome b5 reductase enzyme. This infant was found to be blue at a routine newborn follow-up visit. sepsis, structural congenital heart disease, prenatal administration, and ingestion of oxidant dyes were excluded as a cause of the cyanosis by history and appropriate tests. Chocolate discoloration of arterial blood provided a clue to the diagnosis. A normal newborn screen and hemoglobin electrophoresis made the diagnosis of hemoglobin m unlikely as the cause of the methemoglobinemia (Hb A 59.4%, A2 1.8%, and F 38.8%). Red blood cell enzyme activity and dna analysis revealed a homozygous form of the cytochrome b5 reductase enzyme deficiency. He responded very well to daily methylene blue and ascorbic acid administration, and he has normal growth and developmental parameters, although he shows an exaggerated increase in his methemoglobin level with minor oxidant stress such as diarrhea.- - - - - - - - - - ranking = 1keywords = blood cell (Clic here for more details about this article) |
6/22. New variant of cytochrome b5 reductase deficiency (b5RKurashiki) in red cells, platelets, lymphocytes, and cultured fibroblasts with congenital methemoglobinemia, mental and neurological retardation, and skeletal anomalies.A Japanese man with cytochrome b5 reductase (b5R) deficiency in various blood cell lineages (red cells, platelets, and lymphocytes) and in cultured fibroblasts demonstrated congenital methemoglobinemia associated with mental and neurological retardation, and various skeletal anomalies, such as spondylosis deformans and finger joint deformations, which have never been described in association with this enzyme deficiency. Cytochrome b5 reductase deficiency was most severe in red cells (0.3-4%) and less marked in platelets (13-27%), lymphocytes (18-31%), and fibroblasts (50%). The present case appears to be a new variant of cytochrome b5 reductase deficiency (b5RKurashiki).- - - - - - - - - - ranking = 1keywords = blood cell (Clic here for more details about this article) |
7/22. dapsone-induced methemoglobinemia and hemolytic anemia.The treatment of two common adverse effects of dapsone (methemoglobinemia and hemolytic anemia) is discussed, and a case of acute dapsone intoxication is described. A pregnant 29-year-old woman was admitted to an emergency room three hours after ingesting 50 tablets of dapsone (100 mg each) and six alcoholic drinks. One hour after admission 50 g of activated charcoal was given p.o., and 65 mg of methylene blue was given i.v. The patient was found to have a methemoglobin concentration of 25.1%. Arterial blood gases while the patient was breathing 4 L/min of oxygen by nasal cannula were PO2, 136 mm Hg (72.1% saturation); PCO2, 28.9 mm Hg; bicarbonate content, 18.9 mmol/L; and pH, 7.42. oxygen therapy was changed to 100% oxygen by face mask, 50 g of activated charcoal in sorbitol was administered p.o., and another 65 mg of methylene blue was given i.v. Two more 50-g doses of activated charcoal in sorbitol were given (18.5 and 22 hours after dapsone ingestion). methylene blue 130 mg was given 14 hours after dapsone ingestion, and 65 mg was given 21, 36, and 55.5 hours after ingestion. Methemoglobin concentrations never rose above 20% after the sixth dose of methylene blue. On hospital days 2 and 3, laboratory values were consistent with a diagnosis of hemolytic anemia; the patient received two units of packed red blood cells. The hematocrit decreased over the next three days to 23.9%, and the patient received four units of packed red blood cells.(ABSTRACT TRUNCATED AT 250 WORDS)- - - - - - - - - - ranking = 2keywords = blood cell (Clic here for more details about this article) |
8/22. Acquired methemoglobinemia: a retrospective series of 138 cases at 2 teaching hospitals.Methemoglobin is a form of hemoglobin that does not bind oxygen. When its concentration is elevated in red blood cells, functional anemia and tissue hypoxia may occur. We performed a retrospective case series to describe the cases of acquired methemoglobinemia (methemoglobin level >2%) detected and the clinical circumstances under which they occurred at 2 tertiary care hospitals and affiliated outpatient clinics over 28 months. We surveyed co-oximetry laboratory data to identify patients with methemoglobinemia. We reviewed these patients' medical records to extract the clinical information and context. One hundred thirty-eight cases of acquired methemoglobinemia were detected over the 28 months. There was no gender predisposition, and the condition occurred over a wide range of ages (patients aged 4 days to 86 years). Cases occurred in many areas of the hospital, including outpatient clinics. One fatality and 3 near-fatalities were directly attributable to methemoglobinemia. dapsone was the most common etiology of acquired methemoglobinemia, accounting for 42% of all cases. The mean peak methemoglobin level among these individuals was 7.6%. In 5 of the patients with the most severely elevated levels, 20% benzocaine spray (Hurricaine Topical Anesthetic spray, Beutlich Pharmaceuticals, Waukegan, IL) was the etiology, associated with a mean peak methemoglobin level of 43.8%. Eleven pediatric patients developed methemoglobinemia either from exogenous exposure, such as drugs, or due to serious illness, such as gastrointestinal infections with dehydration. Almost all (94%) patients with methemoglobinemia were anemic. Drugs that cause acquired methemoglobinemia are ubiquitous in both the hospital and the outpatient setting. Acquired methemoglobinemia is a treatable condition that causes significant morbidity and even mortality. We hope that a heightened awareness of methemoglobinemia will result in improved recognition and treatment. primary prevention efforts have the potential to reduce the morbidity and mortality associated with this condition.- - - - - - - - - - ranking = 1keywords = blood cell (Clic here for more details about this article) |
9/22. methemoglobinemia secondary to topical benzocaine use in a lung transplant patient.OBJECTIVE: To report a case of methemoglobinemia secondary to the administration of topical benzocaine spray in an anemic patient who had previously undergone a lung transplant. CASE SUMMARY: A 40-year-old white man with a past medical history significant for lung transplant acutely decompensated following oropharyngeal administration of topical benzocaine spray. Subsequent blood analysis revealed a methemoglobin concentration of 51.2%. Following the administration of a single dose of methylene blue 2 mg/kg intravenously, the patient's respiratory status dramatically improved and stabilized. DISCUSSION: methemoglobinemia is a rare but potentially fatal condition that may be either acquired or congenital; however, the disorder is most commonly acquired secondary to exposure to oxidizing chemicals, which are often routinely prescribed medications, including benzocaine. benzocaine can react with hemoglobin to form methemoglobin at a rate that exceeds reduction capabilities, which may result in oxygenation difficulty and respiratory distress. In severe or symptomatic methemoglobinemia, the treatment of choice is methylene blue. CONCLUSIONS: Application of the Naranjo probability scale established a highly probable relationship between topical benzocaine spray and methemoglobinemia and associated respiratory compromise. The risks of palliative use of topical benzocaine in patients with preexisting disorders that compromise oxygen delivery may outweigh any benefit. In our patient, anemia and lung disease increased his risk for clinically significant adverse respiratory events secondary to deficiencies or interferences in oxygen delivery. Topical benzocaine should be administered with caution and careful monitoring in such patient populations.- - - - - - - - - - ranking = 0.011920357043008keywords = white (Clic here for more details about this article) |
10/22. benzocaine-induced methemoglobinemia during transesophageal echocardiography.Acquired or toxic methemoglobinemia is an uncommon complication of topically administered anesthetic agents in patients of all ages-but particularly in pediatric and elderly patients. This report describes a case of acquired methemoglobinemia that occurred after benzocaine spray was applied orally to a 69-year-old white woman weighing 175 lb who was undergoing transesophageal echocardiography. patient care was successfully managed. Fundamental concepts regarding methemoglobinemia are also reviewed to heighten physician awareness of this potentially life-threatening complication associated with the application of common topical anesthetic agents.- - - - - - - - - - ranking = 0.011920357043008keywords = white (Clic here for more details about this article) |
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