A normal karyotype is usually present in cases of classic paroxysmal nocturnal hemoglobinuria (PNH), whereas chromosomal abnormalities involving chromosome bands 13q12 to 13q14 (13q12q14) are frequently found in various hematologic malignancies, including chronic lymphoblastic leukemia (CLL) and myelodysplastic syndrome (MDS). Here, we present a case of a 55-year-old male patient with PNH who had a deletion of chromosome 13q [del(13q)]. He presented with cough, fever, and pancytopenia. Flow cytometry of the patient\'s peripheral blood demonstrated that 21.7% and 21.5% of the erythrocytes were CD59 and CD55 deficient, respectively, and 63.5% of the granulocytes were FLAER and CD24 deficient. Examination of the bone marrow indicated that blasts were not increased but mild dyshematopoietic features were present. Conventional cytogenetic analysis and fluorescence in situ hybridization revealed a deletion of chromosome 13q (q12q14). The patient received an allogeneic hematopoietic stem cell transplantation. Whether this abnormality can be considered as an evidence of MDS in the setting of overt PNH requires an evaluation in the future.

Paroxysmal nocturnal haemoglobinuria (PNH) is an acquired haemopoietic stem cell disorder arising from somatic mutation of the X-linked PIG-A gene which leads to deficiency of the glycosylphosphatidylinositol (GP1) membrane anchor proteins such as CD 59 (MIRL: membrane inhibitor of reactive lysis) and CD 55 (DAF: decay accelerating factor). Allogeneic peripheral blood stem cell transplant (PBSCT) is a curative mode of treatment in symptomatic PNH patients. Assessment of donor chimerism for PBSCT can be performed by various methods including short tandem repeat loci (STR) and variable number of tandem repeats (VNTR). Flow cytometry, which is much cheaper and faster, also can be used to assess engraftment in patients with PNH. Engrafted patients will show the presence of CD 55 and CD 59 on their red cells and white cells. We describe here the usefulness of flow cytometry in the assessment of donor chimerism following allogeneic PBSCT, in a case of PNH.

BACKGROUND: The Inab phenotype is a rare deficiency of all Cromer antigens. These antigens are carried on the decay-accelerating factor (DAF, CD55) molecule that is attached to the red blood cell (RBC) membrane by a glycosylphosphatidylinositol (GPI) anchor. Although typically inherited, an acquired and transient form of the Inab phenotype also exists. A patient with the triad of transient Inab phenotype, a direct-agglutinating anti-IFC, and gastrointestinal (GI) abnormalities is reported.
METHODS: An 18-month-old boy with gastroesophageal reflux disease requiring a feeding tube, milk and soy intolerance, and severe growth retardation, as well as vision and hearing deficits from cytomegalovirus infection, was identified when pretransfusion testing revealed a potent panagglutinin (titer > 2000 at 4 degrees C). This antibody did not react with Dr(a-) and IFC RBCs, and the autocontrol was negative. The patient\'s RBCs lacked CD55 by flow cytometric techniques but had normal levels of CD59 and antigens such as Yt(a) and Emm, carried on GPI-linked proteins, thus excluding paroxysmal nocturnal hemoglobinuria. Several months after initial detection, the anti-IFC was virtually undetectable and his cells reacted weakly with anti-IFC, anti-Dr(a), and anti-CD55. RBCs from the propositus\' parents and brother demonstrated normal CD55 and CD59 expression.
CONCLUSIONS: This is the first example of a direct-agglutinating anti-IFC. The cause of the transient depression in CD55 protein (and thus Cromer system antigens) and appearance of anti-IFC remains unknown, as does the relationship between the patient\'s GI system abnormalities and these serologic findings.

Using flow cytometry, decay-accelerating factor (DAF) and CD59 have been measured in peripheral blood cells of 11 patients with aplastic anaemia and 34 healthy controls. Ten of the patients had monophasic fluorescence profiles similar to those of the controls. However, one patient had small DAF- and CD59-negative populations in granulocytes and monocytes, but not in erythrocytes. One year after the first assay, a second flow cytometric study revealed that all peripheral blood cell species, including erythrocytes, contained DAF- and CD59-deficient populations. At this time, a sucrose haemolysis test was positive. This is the first reported case of aplastic anaemia-PNH syndrome in which DAF- and CD59-negative cells appeared first in granulocytes and monocytes and later in all types of peripheral blood cells.

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