Yih-Ming Yang

Causes of death in sickle cell disease: an autopsy study

Summary. More precise analysis of causes of death is needed to focus research efforts and improve morbidity and mortality in sickle cell disease. In this study, the morphological evidence of the cause of death was studied in 306 autopsies of sickle cell disease, which were accrued between 1929 and 1996. The most common cause of death for all sickle variants and for all age groups was infection (33–48%). The terminal infection was heralded by upper respiratory tract syndromes in 72·6% and by gastroenteritis in 13·7%. The most frequent portal of entry in children was the respiratory tract but, in adults, a site of severe chronic organ injury. Other causes of death included stroke 9·8%, therapy complications 7·0%, splenic sequestration 6·6%, pulmonary emboli/thrombi 4·9%, renal failure 4·1%, pulmonary hypertension 2·9%, hepatic failure 0·8%, massive haemolysis/red cell aplasia 0·4% and left ventricular failure 0·4%. Death was frequently sudden and unexpected (40·8%) or occurred within 24 h after presentation (28·4%), and was usually associated with acute events (63·3%). This study shows that the first 24 h after presentation for medical care is an especially perilous time for patients with sickle cell disease and an acute event. Close monitoring and prompt aggressive treatment are warranted.

Acute splenic sequestration crisis in sickle cell disease: Early detection and treatment

Acute splenic sequestration crisis (ASSC) in children with various forms of sickle cell disease can result in life-threatening circulatory collapse due to the loss of circulating blood volume. Over a 6-year period we have treated 12 patients ranging in age from 5 1/2 months to 7 years presenting with acute sequestration crisis. Eleven had homozygous sickle cell disease and the other had sickle-thalassemia. One patient died of acute circulatory collapse. Eight patients underwent splenectomy after a major episode of sequestration with no serious infectious complications up to 5 years following splenectomy. Three patients with minor episodes have been followed with no recurrences. To foster early detection of this potentially lethal complication of sickle cell disease, an educational program in our Comprehensive Sickle Cell Center instructs the parents to examine the spleen and bring their child in for evaluation if the spleen enlarges. A newly developed videotape describes the common symptoms of ASSC and illustrates the technique of palpating the spleen. With early detection of sickle cell disease by neonatal screening and the educational program, the morbidity and mortality from this complication of sickle cell disease can be reduced.

Cobalamin malabsorption in three siblings due to an abnormal intrinsic factor that is markedly susceptible to acid and proteolysis.

Three siblings presented in their second year of life with megaloblastic anemia that responded to parenteral cobalamin (Cbl). Schilling tests were less than 1%, correcting to 5 to 15% after addition of hog intrinsic factor (IF). Gastric acid analysis and gastric biopsies were normal by light and electron microscopy. Gastric juice contained less than 3 pmol/ml of Cbl-binding ability due to IF (normal, 10-34 pmol/ml) and less than 2 pmol/ml of IF when measured with a radioimmunoassay (RIA) using normal human IF-[57Co]Cbl and rabbit anti-human IF serum (normal, 17-66 pmol/ml). However, RIA employing rabbit anti-hog IF serum gave values of 4-13 pmol/ml of IF (normal, 11-33 pmol/ml). This material had an apparent molecular weight of 40,000 (normal IF = 70,000). The IF from gastric biopsies appeared normal in terms of Cbl-binding ability, ileal binding, molecular weight, and both RIAs. This IF differed from normal mucosal IF, in that it lost its Cbl-binding ability when incubated at 37 degrees C at acid pH or in the presence of pepsin or trypsin. This loss was retarded when [57Co]Cbl was bound to the IF before these incubations. The stabilizing effects of neutralization and Cbl were also demonstrated in vivo. Schilling tests for the siblings of 0.4, 0.5, and 1.0% increased to 2.7, 5.7, and 4.3% (P less than 0.05), respectively, when the Schilling tests were repeated with the addition of NaHCO3 and cobinamide (which allows Cbl to bind immediately to IF). We conclude that Cbl malabsorption in these children is due to an abnormal IF that is markedly susceptible to acid and proteolytic enzymes which cause a decrease in its molecular weight and Cbl-binding ability and a loss of antigenic determinants that are recognized by the anti-human IF serum.

BFU‐E colony growth in response to hydroxyurea: Correlation between in vitro and in vivo fetal hemoglobin induction

Patients with sickle‐cell anemia treated with hydroxyurea may have significant reduction in frequency and severity of pain episodes. However, previous clinical trials show a variable response to hydroxyurea. Criteria which can be used to select patients who are likely to respond to hydroxyurea treatment would be useful. Our laboratory has previously demonstrated an inverse linear relationship between the total number of burst‐forming unit‐erythroid (BFU‐E) colonies and fetal hemoglobin levels in sickle‐cell patients treated with hydroxyurea. In the present report, an in vitro cell culture system was established to evaluate the effects of hydroxyurea on BFU‐E colony growth and induction of fetal hemoglobin production. Five Hb SS patients who were not previously treated with hydroxyurea and three Hb SS patients who failed to respond to hydroxyurea treatment were included in the study. The results show that the number of BFU‐E colonies is decreased from 153.7 to 7.2 per 3 × 105 mononuclear cells, whereas fetal hemoglobin levels were increased from 5.1 to 19.4% in the presence of hydroxyurea in vitro in cultured erythroid progenitors, which were derived from 5 patients before treatment. The number of BFU‐E colonies decreased from 153.7 to 2.0 per 3 × 105 mononuclear cells in the in vitro cultures obtained from serial peripheral blood samples over a 9‐ to 20‐week period of oral hydroxyurea therapy. A simultaneous rise in fetal hemoglobin level from 10.2 to 28.6% in the peripheral blood over the same period of hydroxyurea therapy was also observed. Our results demonstrate that the increase in fetal hemoglobin levels in cells treated with hydroxyurea in vitro is comparable to the rise of fetal hemoglobin production following hydroxyurea therapy in these patients. On the contrary, these findings were not observed in three previously non‐responsive sickle‐cell patients. These results suggest that the changes in number of BFU‐E colonies and fetal hemoglobin levels after in vitro exposure to hydroxyurea may be a useful approach to select sickle‐cell patients who will respond to hydroxyurea therapy. Am. J. Hematol. 56:252–258, 1997.

Mechanism for fetal hemoglobin induction by hydroxyurea in sickle cell erythroid progenitors

Hydroxyurea (HU) is a widely used cytotoxic agent that is known to induce fetal hemoglobin (HbF) production and is presently used to ameliorate the severity of pain episodes in patients with sickle cell anemia (HbSS). Previously we have shown that HU inhibits growth of burst forming unit–erythroid (BFU‐E) colonies in a dose‐dependent manner, while fetal hemoglobin levels were increased. In the present report, we extended our analysis demonstrating the number of S phase cells is significantly higher for HbSS patients that respond to HU therapy. Studies were completed in vitro using erythroid progenitors derived from umbilical cord samples or peripheral blood from patients with HbS–hereditary persistence of fetal hemoglobin (HbS‐HPFH) or HbSS disease. The effect of HU on (a) S phase erythroid progenitors, (b) BFU‐E colony growth, (c) HbF levels in BFU‐E colonies, and (d) total cellular RNA synthesis was analyzed in vitro for the three groups. The level of S phase erythroid progenitors was similar for all three groups and BFU‐E colony growth was inhibited 92–94% for all samples in a dose‐dependent manner. The HbF levels were increased in BFU‐E colonies from HbSS patients (control, 4.0% ± 1.15% vs. +HU, 22.67% ± 2.03%) whereas HbF levels were decreased in BFU‐E colonies derived from umbilical cord samples (control, 80% ± 9.07% vs. +HU, 35.7% ± 4.81%) or HbS‐HPFH patients (control, 49.67% ± 3.84% vs. +HU, 23.3% ± 0.88%). Total RNA synthesis measured by 3H‐uridine incorporation increased with increasing concentrations of HU; however, actinomycin D inhibited HU‐induced RNA synthesis. These results suggest that HU can inhibit an active globin gene without preference and that newly synthesized RNA is under transcriptional control mechanisms. Am. J. Hematol. 65:227–233, 2000.

Maternal-fetal transport of vitamin K1 and its effects on coagulation in premature infants

We conducted a prospective study to determine (1) the maternal-fetal vitamin K1 transport in premature infants after vitamin K1 was given to the mothers antenatally and (2) the vitamin K1 effects on blood coagulation in the babies. Women in labor at less than or equal to 34 weeks of gestation were randomly selected to receive antenatal vitamin K1, 5 mg given intramuscularly (vitamin K1 group), or no vitamin K1 (control group). Eight infants, including one set of twins, were in the vitamin K1 group and six in the control group. Vitamin K1 concentrations were higher in the vitamin K1 group than in the control group (p = 0.06). Activated partial thromboplastin time was prolonged, and factor II coagulation activity and factor II antigen were proportionately decreased in cord plasma in both groups. The average ratio of factor II coagulation activity to antigen was not decreased in either group. Protein induced by vitamin K absence-II (PIVKA-II) was not detectable in any cord plasma sample in either group. These findings support previous reports that the decreased vitamin K-dependent coagulation activity in premature infants is the result of reduced synthesis of precursor proteins, rather than the result of vitamin K deficiency, and suggest that additional vitamin K1 is not likely to improve coagulation activity. Among those infants who underwent cranial ultrasonography, all four in the vitamin K1 group and one of five in the control group had mild intraventricular hemorrhage. Studies of a larger number of patients are necessary before it can be established that maternal antenatal administration of vitamin K1 results in improvement of coagulation and the prevention of intraventricular hemorrhage in premature infants.

Pharmacologic Induction of Fetal Hemoglobin Synthesis: Cellular and Molecular Mechanisms

The switch from embryonic to fetal then to adult hemoglobin synthesis is a unique phenomenon during early human development. Fetal hemoglobin (Hb F) is known to interfere with polymerization of Hb S in erythrocytes. Several pharmacologic agents such as 5–azacytidine, myleran, hydroxyurea, erthropoietin, and butyrates enhance fetal hemoglobin production and have been used in hemoglobinopathy patients to ameliorate severe pain episodes and reduce severe anemia. Among these, hydroxyurea is the agent of choice because of its safety and ease of administration. One of the primary cellular mechanisms involved in pharmacologic induction of Hb F synthesis is rapid regeneration of erythroid precursors following the cytoreduction phase of certain pharmacologic agents. Molecular mechanisms involving changes in chromatin structure and/or transcription factor binding have been demonstrated for γ gene induction by butyrate. Identifying the proteins involved in γ gene activation by various compounds may offer a new strategy for gene therapy to cure hemoglobinopathy disorders.

Tumoral calcinosis in an infant

Abstract We report tumoral calcinosis, an uncommon disease of uncertain origin, in an infant – only the sixth instance of the disease reported in this age group. The radiologic features are typical as illustrated by three modalities. The clinical, radiologic and pathologic features are discussed along with comments concerning possible etiologies and management.

Magnetic resonance imaging of bone marrow in sickle cell patients.

Assessment of the bone marrow in sickle cell patients with or without pain crises can be accomplished using a variety of imaging techniques. Conventional radiography is the least sensitive of all imaging modalities in the early stages of the bone marrow infarct. Radionuclide imaging using 99mTc sulfur colloid shows sharply demarcated photon-deficient regions that are slow to resolve. Cumulative exposure to ionizing radiation would be of concern if repeated examinations with conventional x-rays and radionuclides were carried out. Magnetic resonance imaging (MRI) is a noninvasive technique that differentiates the bone marrow of sickle cell patients from that of normal controls. Furthermore, at least in some patients, acute tissue changes can be detected during early stages of pain crises using magnetic resonance. Further investigations are necessary to optimize the use of MRI in sickle cell patients with pain crises.

Granulocyte Colony-Stimulating Factor Associated Leukocytoclastic Vasculitis Mimicking Henoch-Schonlein Purpura

Human granulocyte colony-stimulating factor (G-CSF) is one of the hematopoietic growth factors that is used for the reduction of neutropenia in cancer patients receiving myelosuppressive chemotherapy and in patients with congenital and cyclic neutropenia. Adverse effects associated with the use of G-CSF, such as bone pain, are usually mild and transient. We report a more serious and disturbing association, leukocytoclastic vasculitis, which manifested as a cutaneous purpuric lesion with painful joints and mimicked Henoch-Schonlein purpura.