Severe combined immunodeficiency (SCID) in man: B cell-negative (B-) SCID patients exhibit an irregular recombination pattern at the JH locus.

Human severe combined immunodeficiency (SCID) patients were analyzed by a polymerase chain reaction assay for their recombination capability at the DHQ52-JH region of the immunoglobulin heavy chain locus. Five patients with B cells (B+ SCID) exhibited a recombination pattern also observed in healthy persons. In contrast, six patients lacking B cells (B- SCID) showed a grossly altered rearrangement pattern characterized by the (partial) absence of regular DHQ52-JH recombinations and the presence of abnormal rearrangements. These events were caused by deletions surpassing the boundaries of immunoglobulin coding elements and thus resemble the pattern of deletional recombinations previously described in SCID mice.

Hemoglobin Freiburg: abnormal hemoglobin due to deletion of a single amino acid residue.

Structural characterization of a new variant of human hemoglobin (adult), designated hemoglobin Freiburg, indicates the deletion of the valyl residue No. 23 from an otherwise normal beta-chain. The formula may be written (alpha2)beta(2)(23val-0). The abnormal hemoglobin is present with hemoglobin A in the proposita and in two of her three living children, but is not detectable in her parents. We postulate that this variant represents a triplet base deletion which most likely resulted from an unequal crossing-over between two normal betachain loci during meiosis in one of the parents of the proposita.

The proximal element of the beta globin locus control region is not functionally required in vivo.

In addition to local sequence elements the regulation of the high-level, development- and tissue-specific expression of the human beta globin gene cluster appears to require distant regulatory sequences which have been termed locus control region. In the chromatin of erythroid cells the locus control region is characterized by four DNaseI hypersensitive sites that are located 6-18 kb 5' of the epsilon globin gene. The definition of the sequences minimally required for locus control region activity is likely to further the understanding of its physiology and will be of interest for the development of somatic gene therapy strategies of the hemoglobinopathies. We present here the analysis of a family with a 3,030-bp deletion of sequences upstream of the epsilon globin gene including the most 3' locus control region element and cosegregating beta(0) thalassemia. The deletion is linked in cis to a structurally and functionally normal beta globin gene. The proximal element of the locus control region does not therefore appear to be necessary for beta globin gene activity in vivo.

Involvement of chromosome 9 in variant Ph1 translocation.

Cytogenetic analysis of a patient with chronic myelocytic leukemia revealed a translocation (21; 22) (q 22; q 11) without a detectable involvement of chromosome 9. By in-situ hybridization studies, however, we demonstrate a reciprocal translocation of sequences from chromosome 9 (c-abl) to Ph1 and chromosome 22 (bcr) to 9, respectively. These observations suggest a consistent participation of chromosome 9 in the Ph1 translocation, regardless of the cytogenetic subtype.

Additional c-abl/bcr rearrangements in a CML patient exhibiting two ph1 chromosomes during blast crisis.

Recent data suggest that two human genes, c-abl on chromosome 9 and bcr on chromosome 22, are involved in the generation of Ph1-positive CML. To examine a possible role of these sequences in transition from chronic towards blastic phase, rearrangements within bcr were analysed in 4 patients with Ph1-positive CML during chronic and acute phase. In 3 patients bcr rearrangements were identical in both phases, while in a fourth patient with duplicated Ph1 an amplified additional bcr fragment was detected in acute phase. Northern blot analysis of blast cells of the latter patient showed a novel 10.3 kb RNA species that replaced the altered 8 kb RNA transcript usually found in Ph1-positive CML.

Conversion of acute undifferentiated leukemia phenotypes: analysis of clonal development.

The cellular origin of acute undifferentiated leukemia (AUL) is still a matter of controversy. We report on two cases in which the diagnosis of AUL was established according to restricted criteria. Blast cells of both patients showed phenotypic conversion during the course of disease. In one case, within 24 days from starting treatment, the leukemic phenotype changed from AUL to acute myelomonocytic leukemia (FAB L1, TdT+ to FAB M4, TdT-). The initial phenotype of this acute leukemia was characterized by the co-expression of both B-lymphoid and myeloid markers on the same cell. Moreover, analysis of esterase isoenzyme pattern showed the whole spectrum of isoenzymes typically seen in myelomonocytic leukemias already at diagnosis, yet blast cells additionally contained all three isoenzymes of beta-hexosaminidase typically seen in AUL. However, examination of immunoglobulin (Ig) heavy chain gene rearrangement initially and after conversion revealed an identical monoclonal configuration of Ig heavy chain sequences in both samples. The second AUL patient relapsed after allogeneic bone marrow transplantation with common ALL-antigen (CALLA) positive acute leukemia. Subsequent Southern blot analysis showed a novel rearranged Ig fragment compared to the analysis before transplantation indicating that the leukemic clones prior to and after transplantation were not identical. No chromosomal abnormalities were observed in both cases. These data support the view that AUL cells originate from a pluripotent stem cell that is capable to differentiate in the myelomonocytic lineage (patient 1), and confirm the value of Ig gene analysis as marker for cellular clonality.

[Ocular findings in Desferal therapy]. / Okuläre Befunde bei Desferaltherapie.

Desferrioxamine (DFO) is the most important drug in the treatment of thalassemia major and other hematological diseases requiring regular transfusion. It eliminates excessive ferritin by building up chelate complexes. Different mechanisms of possible DFO toxicity are induction of oxidation, damage of the blood-retina barrier, or reduction in other metalloions (Cu2+, Zn2+). The objective of the present study was to evaluate the ocular side effects of DFO treatment. We prospectively examined 17 patients aged 5 to 25 years, all of them treated with DFO. Visual acuity, pupillary reaction, anterior segment, lens and fundus were checked. If possible, visual fields, color vision, dark adaptation, stereoscopic vision, and contrast sensitivity were investigated. Lens opacities were found in 41% (7/17), changes in the retinal pigment epithelium in 35% (6/17), tortuosity of retinal vessels in 24% (4/17), dilation and sheathing of the retinal vessels in 18% (3/17), defects in color vision in 29% (5/17), and abnormal dark adaptation in 18% (3/17) of the patients. The oculotoxicity of DFO is dose-dependent. Major side effects like depression of the visual acuity are partially reversible after discontinuing the therapy. Regular ophthalmological check-ups are therefore necessary.

[Diagnosis and treatment of aplastic anemia]. / Diagnostik und Behandlung der aplastischen Anämie.

Severe aplastic anemia is a rare disorder in childhood. Among various therapeutical strategies bone marrow transplantation (BMT) and immunosuppressive treatment with antithymocyte globulin (ATG) have proven to be most successful. Priority should be given to BMT over ATG treatment for patients with HLA-identical donors. Patients with Fanconi's anemia require a reduced conditioning program with cyclophosphamide and irradiation for BMT. Own experiences indicate that cooperative studies are highly needed to improve medical care for patients with severe aplastic anemia.

The preleukemic syndromes (hematopoietic dysplasia) in childhood.

The preleukemic syndrome or hematopoietic dysplasia is a marrow stem-cell disorder with clinically recognizable hematologic abnormalities which precede the development of acute nonlymphocytic leukemia. Its occurrence in childhood is extremely rare; seven "true" cases who fulfill all the criteria for the disorder have been reported until now. The preleukemic syndrome is generally characterized by peripheral cytopenia with fairly specific morphologic abnormalities in cell differentiation. The hematological and clinical features permit recognition of preleukemia even before the development of overt leukemia. Experimental data indicate that preleukemia is an "early" leukemic syndrome in which hematopoietic cell differentiation becomes progressively impaired with termination in the nearly complete maturation block which is characteristic of acute myelogenous leukemia.

[Diagnostic and therapeutic applications of gene technology methods in thalassemia]. / Diagnostik und Therapieansätze mit gentechnologischen Methoden bei Thalassämien.

By applying gene technology, great progress has been made in defining the molecular basis of thalassemias. While the prevention of thalassemias through prenatal diagnosis has improved significantly, advances for molecular therapy have been rather limited until now.

Undetectable IgG4 in immunoprecipitation: association with repeated infections in children?

A total of 210 patients with repeated infections were screened for IgG4 deficiency. In 30 patients (14%) IgG4 was undetectable by radial immunodiffusion (less than 30 mg/l). Of these patients 17 (57%) were less than 2 years of age. Concomitant IgA deficiency (IgA less than 0.05 g/l) was demonstrated in 11 cases (37%). IgG2 serum levels below the normal range were found in 26 children. IgG4 could be demonstrated at a concentration of 0.5-29 mg/l in all 30 patients using a more sensitive enzyme-linked immunosorbent assay technique. Although a highly selected group of patients was investigated, the percentage of individuals without detectable IgG4 by immunodiffusion was in the same range as reported in the literature for healthy control persons. It is thus concluded that IgG4 serum reference levels have to be defined using more sensitive methods and that the observed severe infections are more likely to be connected with low serum IgG2 and/or IgA levels than undetectable IgG4 as measured by immunodiffusion.