ABSTRACT: Paroxysmal nocturnal hemoglobinuria (PNH) is a hematologic disorder characterized by acquired PIG-A gene mutations that lead to defective bioassembly of glycosylphosphatidylinositol (GPI) anchors and the absence of GPI-linked surface proteins. As the etiology of these acquired PIG-A gene mutations is unknown, we hypothesized that patients with PNH have overall genetic instability and acquire somatic mutations throughout their genome. We first analyzed microsatellite sequences and found equivalent size variation using DNA from GPI-negative granulocytes compared with the DNA of paired GPI-positive B cell lines or normal granulocytes. We next quantitated the frequency of mutations at the hypoxanthine-guanine phosphoribosyl transferase (hprt) gene locus, and found 1 PNH patient with a large increase in hprt mutant frequency (256.7 x 10-6 vs. 27.8 +/- 19.9 x 10-6 for normal adults) that was confirmed on 4 independent blood samples. We also quantitated "illegitimate" VDJ genetic recombination events between the T cell receptor V-gamma and J beta gene loci, and found a second PNH patient with a large increase (43.5 events per microgram of DNA vs. 1.3 +/- 0.8 events per microgram of DNA for normal adults), confirmed on 4 independent DNA samples. Both of these PNH patients are young females with no history of aplastic anemia. Our data show that PNH patients can have increased numbers of acquired somatic mutations in gene loci distinct from PIG-A. These data suggest that genetic instability may be associated with the development of PIG-A mutations that lead to the clinical picture of PNH.

Reprint requests to: Russell E. Ware, M.D.,Ph.D., P.O. Box 2916, DUMC, Durham, North Carolina 27710, phone: (919) 684-5665, fax: (919) 684-5752, e-mail: ware0005@mc.duke.edu.

ABSTRACT: Imiglucerase, the recombinantly produced enzyme, is gradually replacing the human placental derived alglucerase in the treatment of Gaucher patients. We describe the first case, to the best of our knowledge, of an anaphylactoid reaction to imiglucerase in a patient who tolerated alglucerase. The patient was diagnosed at the age of 24-1/2 years with anemia and hepatosplenomegaly. Over the years he had suffered from marked splenomegaly, thrombocytopenia and recurrent bleeding episodes. At the age of 24 he started treatment with imiglucerase. After 3 months of treatment, immediately after starting an infusion, he experienced flushing, cough, tachycardia, palpitation, chest pain and excessive sweating, which reoccurred on a consecutive administration. Substitution with alglucerase was tolerated well, with only mild rash when he was premedicated with benadryl. Immediate skin tests to alglucerase, imiglucerase and gelatin were negative. IgG against alglucerase was undetectable. The in vitro mast cell degranulation test was positive for alglucerase, imiglucerase haemaccel (a gelatin based plasma substitute, which is a component of imiglucerase). This sensitivity to imiglucerase but not to alglucerase, raises the question of future treatment for this patient, since the production of alglucerase may cease, once imiglucerase production will cover the need for replacement enzyme.

Keywords: Gaucher disease, Alglucerase, Imiglucerase, sensitivity, anaphylactoid reaction.

Reprint requests to: S. Aviner, Hematology & Oncology Department, Schneider Children's Medical of Israel, Petach Tikva 49202, ISRAEL.