Fe Chen

Genetic and clinical features of hemoglobin H disease in Chinese patients

BACKGROUND Normally, one pair of each of the two alpha-globin genes, alpha1 and alpha2, resides on each copy of chromosome 16. In hemoglobin H disease, three of these four alpha-globin genes are affected by a deletion, a mutation, or both. We studied the alpha1-globin gene abnormalities and the clinical and hematologic features of Chinese patients with hemoglobin H disease in Hong Kong. METHODS We assessed the clinical features, hematologic values, serum ferritin levels, and liver function of 114 patients with hemoglobin H disease. We also performed echocardiography and magnetic resonance imaging of the liver and examined the two pairs of alpha-globin genes. RESULTS Hemoglobin H disease in 87 of the 114 patients (76 percent) was due to the deletion of three of the four alpha-globin genes (--/-alpha), a combination termed the deletional type of hemoglobin H. The remaining 27 patients (24 percent) had the nondeletional type of hemoglobin H disease, in which two alpha-globin genes are deleted and a third is mutated (--/alphaalphaT). All 87 patients with the deletional type of hemoglobin H were double heterozygotes in whom there was a deletion of both alpha-globin genes from one chromosome, plus a deletion of the alpha1 or alpha2 gene from the other chromosome (--/alpha- or --/-alpha). A variety of mutated alpha-globin genes was found in the patients with nondeletional type of hemoglobin H disease. Patients with the nondeletional type of the H disease had more symptoms at a younger age, more severe hemolytic anemia, and larger spleens and were more likely to require transfusions than patients with deletional hemoglobin H disease. The severity of iron overload was not related to the genotype. CONCLUSIONS Chinese patients in Hong Kong with the nondeletional type of hemoglobin H disease have more severe disease than those with the deletional type of the disease. Iron overload is a major cause of disability in both forms of the disease.

Human herpesvirus 6 and human herpesvirus 7 infections in bone marrow transplant recipients

Human cytomegalovirus (HCMV), human herpesvirus‐6 (HHV‐6), and human herpesvirus‐7 (HHV‐7) DNA in peripheral blood leukocytes (PBL) of 61 bone marrow transplant recipients was monitored weekly during the first 12 weeks post‐transplantation by a nested polymerase chain reaction (PCR). Thirty‐seven (61%), 17 (28%), and 32 (53%) of patients had one or more PBL specimens positive for HCMV, HHV‐6 or HHV‐7 DNA, respectively. HHV‐7 DNA in PBL during the early post‐transplant period was associated with a longer time to neutrophil engraftment (mean 28.8 days vs 19.8 days; P = 0.01). In two patients who failed to engraft, HHV‐6 DNA and HHV‐7 DNA was detected in plasma and PBL, respectively, early in their post‐transplant period. Patients with HCMV disease were more likely to have concurrent HHV‐7 DNA in PBL prior to onset of disease than were patients with asymptomatic HCMV infection, suggesting that HHV‐7 may be a cofactor in the progression from HCMV infection to HCMV disease. In the 17 patients (179 specimens) in whom viral DNA in plasma was studied (in addition to PBL), a positive result was found only in 3. In each, viral DNA in plasma appeared to correlate with clinically significant disease. HHV‐7 DNA in plasma was associated with encephalitis in an allograft recipient. J. Med. Virol. 53:295–305, 1997.

In vitro susceptibility of 10 clinical isolates of SARS coronavirus to selected antiviral compounds.

Abstract Effective antiviral agents are urgently needed to combat the possible return of severe acute respiratory syndrome (SARS). Commercial antiviral agents and pure chemical compounds extracted from traditional Chinese medicinal herbs were screened against 10 clinical isolates of SARS coronavirus by neutralisation tests with confirmation by plaque reduction assays. Interferon-beta-1a, leukocytic interferon-alpha, ribavirin, lopinavir, rimantadine, baicalin and glycyrrhizin showed antiviral activity. The two interferons were only active if the cell lines were pre-incubated with the drugs 16h before viral inoculation. Results were confirmed by plaque reduction assays. Antiviral activity varied with the use of different cell lines. Checkerboard assays for synergy were performed showing combinations of interferon beta-1a or leukocytic interferon-alpha with ribavirin are synergistic. Since the clinical and toxicity profiles of these agents are well known, they should be considered either singly or in combination for prophylaxis or treatment of SARS in randomised placebo controlled trials in future epidemics.

Stage-Specific Manifestation of Mold Infections in Bone Marrow Transplant Recipients: Risk Factors and Clinical Significance of Positive Concentrated Smears

Potassium hydroxide-concentrated smears, prepared from sedimented remains of clinical specimens, were used to distinguish between mold infection and exogenous contamination in fungal culture-positive specimens. This method was applied in the study of 3,857 clinical specimens from 230 bone marrow transplant recipients who were followed up prospectively for infectious complications. Concentrated smears of only 86 (from 21 infected patients) of 149 fungal culture-positive specimens were positive for hyphae; 82 of the strains were Aspergillus species. Concentrated smears of the remaining 63 fungal culture-positive specimens were negative; the strains identified by culture were considered as exogenous contaminants (87% of which were Penicillium species). A stage-specific manifestation of mold infection was observed: 67% of mold infections occurred during acute graft-vs.-host disease (GVHD) a median of 47 days after transplantation, whereas 9% of mold infections occurred as rapidly fatal invasive disease before engraftment. Overall, of the 21 patients with mold infection, 17 (81%) had invasive mold disease, and four (19%) had mold colonization of airways secondary to chronic GVHD after day 100. The significant risk factors for mold infection were total-body irradiation and grade 2-4 acute GVHD. Because of our high mortality rate (82%), the consideration of antimold prophylaxis for such patients may be warranted.

Autologous bone marrow transplantation for primary nasal T/NK cell lymphoma

Primary nasal T or NK cell lymphoma is rarely seen in the Western population but is more common in the Orientals. Although it often presents with localized disease, the prognosis is generally poor. Long-term remission is seen in only 50% of patients with stage I disease despite aggressive treatment with chemotherapy and radiotherapy, and is invariably fatal if disseminated. Conventional chemotherapy for relapsed disease is usually not successful. Since 1992, three patients with relapsed primary nasal T/NK cell lymphoma have received high-dose chemotherapy with autologous bone marrow rescue at Queen Mary Hospital, Hong Kong. High-dose cyclophosphamide, BCNU and etoposide were used for conditioning. Two of them had a favourable response and remained in complete remission at 12 and 44 months post-transplant. The third patient unfortunately had a systemic relapse 6 months after the transplant. It appears from this experience that, like other aggressive non-Hodgkin’s lymphomas, high-dose chemotherapy and autologous bone marrow rescue is an effective treatment for relapsed primary nasal lymphoma following failure of conventional chemotherapy and radiotherapy.

Clinical Significance of Alimentary Tract Microbes in Bone Marrow Transplant Recipients

A prospective study on the microbes isolated from the alimentary tract in 120 bone marrow transplant (BMT) recipients (1991-1993) was undertaken to define the spectrum of organisms isolated under antimicrobial prophylaxis, their temporal sequence of emergence, and the associated morbidity and mortality. Clostridium difficile (n = 20), isolated in the pre-engraftment and early post-engraftment periods (day 2-45 post-BMT), was the most common microbe recovered from stool of patients with diarrhea. In contrast to previous reports, no significant difference in mortality was observed between patients with and without C. difficile isolated in stool. Two patients had neutropenic ileocecitis with concomitant bacteremia due to Escherichia coli and Klebsiella pneumoniae. One patient was found to have astrovirus gastroenteritis (day 7), and Giardia lamblia was recovered from the stool of another (day -7). Heavy growth of Staphylococcus aureus from direct smear-positive specimens was found from the upper airway of two patients with severe mucositis and complete dysphagia (day 12 and 23). Salmonella spp. of groups B and E were found in the stool of five asymptomatic patients at the time of conditioning. No specific organisms was recovered from the endoscopic brushing of two patients with lower end esophagitis, three patients with upper gastrointestinal bleeding, and three patients with perirectal cellulitis. During the post-engraftment period, five patients had documented cytomegalovirus gastroenterocolitis (days 34-97), one had Mycobacterium chelonae colitis (day 70), and another had nodular gastritis due to Acremonium falciforme (day 270). Overall, only 28% of patients with alimentary tract symptoms/syndrome had specific pathogens isolated from clinical specimens. Differentiation of the causation of alimentary tract symptoms was often difficult because noninfectious complications such as conditioning toxicity, graft-versus-host disease, and its treatment often caused alimentary tract symptoms in addition to predisposed BMT patient to infection. The reluctance of obtaining tissue biopsy for ascertaining the importance of those potential alimentary tract pathogens often dictate the use of empirical treatment.

Unique risk factors for bacteraemia in allogeneic bone marrow transplant recipients before and after engraftment

A study of the risk factors associated with bacteraemia in 191 allogeneic bone marrow transplant (BMT) recipients (1991–1996) was performed. In contrast to risk factors commonly cited for cancer chemotherapy, mucositis, degree of conditioning toxicity of the gut and lungs, duration of neutropenia, and severity of neutropenia and monocytopenia were not associated with bacteraemia in the pre-engraftment period, during which the only significant risk factor was late stage underlying disease (P < 0.05). after engraftment, hickman catheter infection, and severe acute and chronic graft-versus-host disease (gvhd) were found to be independently associated with bacteraemia by multivariate analysis (P < 0.001, <0.05 and <0.05, respectively). this might be explained by intense antimicrobial prophylaxis, early empirical treatment, and non-routine use of haemopoietic growth factors. no significant difference in mortality was detected between bacteraemic and non-bacteraemic patients in both periods. allogeneic bmt recipients are therefore a group of patients distinct from other cancer patients receiving chemotherapy at risk of developing bacteraemia. the study findings prompt consideration of a management protocol incorporating early and routine use of haemopoietic growth factors before engraftment in high-risk patients with late stage underlying malignancies, routine antimicrobial prophylaxis for acute gvhd with intense immunosuppression, and intravenous immunoglobulin therapy for chronic gvhd. further cost-benefit analyses are warranted.

Qualitative and Quantitative Magnetic Resonance Imaging in Haemoglobin H Disease: Screening for Iron Overload

OBJECTIVES To evaluate the clinical utility of magnetic resonance imaging (MRI) in screening for iron overload in non-transfusion dependent Haemoglobin (Hb) H disease. PATIENTS AND METHODS Thirty-six non-transfusion dependent HbH patients were evaluated with axial spin echo T1 and gradient echo T2 MRI of the abdomen and heart. The ratios of signal intensities (SIR) of the liver, spleen, pancreas and heart to paraspinous muscles were calculated. SIR <1 was taken as indicative of iron overload. Qualitative grading (0-4 scale) of iron overload was also performed. The relationship between T1 and T2 SIR and serum ferritin, and that between qualitative grading and serum ferritin were examined using standard statistical methods. Comparisons were also made between qualitative grading and quantitative T1 and T2 SIR data in diagnosing iron overload. Six patients underwent liver biopsies. RESULTS T2 SIR was more sensitive in detecting iron overload than T1 SIR. Thirty-three livers, 13 spleens, six pancreas and one heart were diagnosed as having iron overload with T2 SIR, including three patients with normal serum ferritin. A positive diagnosis by T2 SIR was more closely related to that of qualitative grading than T1 SIR. Serum ferritin was negatively correlated with hepatic SIR (T1 and T2), and with T2 SIR of the spleen and pancreas, even after adjustment for age. Liver haemosiderosis was confirmed in all six patients who underwent liver biopsies. Liver iron concentration of only one and a half times the normal was found in one patient with positive MR findings. CONCLUSION MR is a non-invasive, effective method for early detection of iron overload particularly in the liver and spleen. Qualitative grading and quantitative T2 SIR data are equivalent in diagnosing iron overload. Routine screening of non-transfusion dependent HbH patients will identify high risk patients in whom early therapeutic intervention may prevent further complications and morbidity.

Effects of Nitrogen Source and Vitamin B12 on Docosahexaenoic Acid Production by Crypthecodinium Cohnii

The effects of nitrogen sources and vitamin B12 on cell growth and docosahexaenoic acid (DHA, C22:6 ω-3) content of Crypthecodinium cohnii ATCC 30556 were investigated. Among the three nitrogen sources (tryptone, yeast extract and corn steep liquor) used, tryptone was the best nitrogen source for C. cohnii. The highest specific growth rate (0.087 h-1) and DHA content (64.34% of total fatty acids) were achieved at a tryptone concentration of 1 g/l. Vitamin B12 was not an essential nutrient for the growth of C. cohnii. However, an addition of vitamin B12 to the medium exhibited stimulating effect on the growth of the alga as reflected by a higher specific growth rate and a higher biomass concentration. The highest biomass concentration (2.48 g/l) was obtained at a vitamin B12 concentration of 0.75 µg/l. The results suggest that nitrogen source should be properly selected and vitamin B12 should be added in the defined artificial medium for the optimal production of DHA by C. cohnii.