Central nervous system dysfunction and erythrocyte guanosine triphosphate depletion in purine nucleoside phosphorylase deficiency

Unleashing the Power of Induced Pluripotent stem Cells in in vitro Modelling of Lesch-Nyhan Disease

Lesch-Nyhan disease (LND) is a monogenic rare neurodevelopmental disorder caused by a deficiency in hypoxanthine-guanine phosphoribosyltransferase (HPRT), the key enzyme of the purines salvage pathway. Beyond its well-documented metabolic consequences, HPRT deficiency leads to a distinctive neurobehavioral syndrome characterized by motor disabilities, cognitive deficits, and self-injurious behavior. Although various cell and animal models have been developed to investigate LND pathology, none have adequately elucidated the underlying mechanisms of its neurological alterations. Recent advances in human pluripotent stem cell research and in vitro differentiation techniques have ushered in a new era in rare neurodevelopmental disorders research. Pluripotent stem cells, with their ability to propagate indefinitely and to differentiate into virtually any cell type, offer a valuable alternative for modeling rare diseases, allowing for the detection of pathological events from the earliest stages of neuronal network development. Furthermore, the generation of patient-derived induced pluripotent stem cells using reprogramming technology provides an opportunity to develop a disease-relevant model within the context of a patient-specific genome. In this review, we examine current stem cell-based models of LND and assess their potential as optimal models for exploring key pathological molecular events during neurogenesis and for the discovering novel treatment options. We also address the limitations, challenges, and future prospects for improving the use of iPSCs in LND research.

Neurologic Status of Patients with Purine Nucleoside Phosphorylase Deficiency Before and After Hematopoetic Stem Cell Transplantation

BACKGROUND

Purine nucleoside phosphorylase (PNP) deficiency is a rare autosomal recessive combined immunodeficiency. The phenotype is profound T cell deficiency with variable B and NK cell functions and results in recurrent and persistent infections that typically begin in the first year of life. Neurologic findings occur in approximately two-thirds of patients. The mechanism of neurologic abnormalities is unclear. Hematopoietic stem cell transplantation (HSCT) is the only curative treatment for PNP deficiency.

METHODS

We report here six patients from five unrelated families with PNP deficiency treated in two centers in Turkey. We evaluated the neurological status of patients and compared to post-transplantation period if available. Then, we performed PubMed, Google Scholar, and Researchgate searches using the terms "PNP" and "hematopoietic stem cell transplantation" to find all reported cases of PNP transplantation and compared to our cohort.

RESULTS

Six patients were treated in two centers in Turkey. One patient died from post-transplant complications. The other four patients underwent successful HSCT with good immune reconstitution after transplantation (follow-up 21-48 months) and good neurological outcomes. The other patient with a new mutation is still waiting for a matching HLA donor.

DISCUSSION

In PNP deficiency, clinical manifestations are variable, and this disease should be considered in the presence of many different clinical findings. Despite the comorbidities that occurred before transplantation, HSCT currently appears to be the only treatment option for this disease. HSCT not only cures immunologic disorders, but probably also improves or at least stabilizes the neurologic status of patients.

Purine Nucleoside Phosphorylase Deficient Severe Combined Immunodeficiencies: A Case Report and Systematic Review (1975-2022)

Purine nucleoside phosphorylase deficient severe combined immunodeficiency (PNP SCID) is one of the rare autosomal recessive primary immunodeficiency disease, and the data on epidemiology and outcome are limited. We report the successful management of a child with PNP SCID and present a systematic literature review of published case reports, case series, and cohort studies on PNP SCID listed in PubMed, Web of Science, and Scopus from 1975 until March 2022. Forty-one articles were included from the 2432 articles retrieved and included 100 PNP SCID patients worldwide. Most patients presented with recurrent infections, hypogammaglobulinaemia, autoimmune manifestations, and neurological deficits. There were six reported cases of associated malignancies, mainly lymphomas. Twenty-two patients had undergone allogeneic hematopoietic stem cell transplantation with full donor chimerism seen mainly in those receiving matched sibling donors and/or conditioning chemotherapy before the transplant. This research provides a contemporary, comprehensive overview on clinical manifestations, epidemiology, genotype mutations, and transplant outcome of PNP SCID. These data highlight the importance of screening for PNP SCID in cases presented with recurrent infections, hypogammaglobulinaemia, and neurological deficits.

Induced pluripotent stem cells from subjects with Lesch-Nyhan disease

Lesch-Nyhan disease (LND) is an inherited disorder caused by pathogenic variants in the HPRT1 gene, which encodes the purine recycling enzyme hypoxanthine-guanine phosphoribosyltransferase (HGprt). We generated 6 induced pluripotent stem cell (iPSC) lines from 3 individuals with LND, along with 6 control lines from 3 normal individuals. All 12 lines had the characteristics of pluripotent stem cells, as assessed by immunostaining for pluripotency markers, expression of pluripotency genes, and differentiation into the 3 primary germ cell layers. Gene expression profiling with RNAseq demonstrated significant heterogeneity among the lines. Despite this heterogeneity, several anticipated abnormalities were readily detectable across all LND lines, including reduced HPRT1 mRNA. Several unexpected abnormalities were also consistently detectable across the LND lines, including decreases in FAR2P1 and increases in RNF39. Shotgun proteomics also demonstrated several expected abnormalities in the LND lines, such as absence of HGprt protein. The proteomics study also revealed several unexpected abnormalities across the LND lines, including increases in GNAO1 decreases in NSE4A. There was a good but partial correlation between abnormalities revealed by the RNAseq and proteomics methods. Finally, functional studies demonstrated LND lines had no HGprt enzyme activity and resistance to the toxic pro-drug 6-thioguanine. Intracellular purines in the LND lines were normal, but they did not recycle hypoxanthine. These cells provide a novel resource to reveal insights into the relevance of heterogeneity among iPSC lines and applications for modeling LND.

The Broad Clinical Spectrum and Transplant Results of PNP Deficiency

PURPOSE

Purine nucleoside phosphorylase (PNP) is a known yet rare cause of combined immunodeficiency with a heterogeneous clinical presentation. We aim to add to the expanding clinical spectrum of disease, and to summarize the available data on bone marrow transplant for this condition.

METHODS

Data was collected from patient files retrospectively. A review of the literature of hematopoietic stem cell transplantation (HSCT) for PNP deficiency was conducted.

RESULTS

Four patients were treated in two centers in Israel. One patient died of EBV-related lymphoma with CNS involvement prior to transplant. The other three patients underwent successful HSCT with good immune reconstitution post-transplant (follow-up 8-108 months) and excellent neurological outcomes.

CONCLUSION

PNP is a variable immunodeficiency and should be considered in various clinical contexts, with or without neurological manifestations. HSCT offers a good treatment option, with excellent clinical outcomes, when preformed in a timely manner.

The First Purine Nucleoside Phosphorylase Deficiency Patient Resembling IgA Deficiency and a Review of the Literature

Purine nucleoside phosphorylase (PNP) deficiency is a rare autosomal recessive primary immunodeficiency disorder characterized by decreased numbers of T-cells, variable B-cell abnormalities, decreased amount of serum uric acid and PNP enzyme activity. The affected patients usually present with recurrent infections, neurological dysfunction and autoimmune phenomena. In this study, whole-exome sequencing was used to detect mutation in the case suspected of having primary immunodeficiency. We found a homozygous mutation in PNP gene in a girl who is the third case from the national Iranian registry. She had combined immunodeficiency, autoimmune hemolytic anemia and a history of recurrent infections. She developed no neurological dysfunction. She died at the age of 11 after a severe chicken pox infection. PNP deficiency should be considered in late-onset children with recurrent infections, autoimmune disorders without typical neurologic impairment.

SIL1 deficiency causes degenerative changes of peripheral nerves and neuromuscular junctions in fish, mice and human

BACKGROUND

Marinesco-Sjögren Syndrome (MSS) is a rare neuromuscular condition caused by recessive mutations in the SIL1 gene resulting in the absence of functional SIL1 protein, a co-chaperone for the major ER chaperone, BiP. As BiP is decisive for proper protein processing, loss of SIL1 results in the accumulation of misshaped proteins. This accumulation likely damages and destroys cells in vulnerable tissues, leading to congenital cataracts, cerebellar ataxia, vacuolar myopathy and other MSS phenotypes. Whether the peripheral nervous system (PNS) is affected in MSS has not been conclusively shown.

METHODS

To study PNS vulnerability in MSS, intramuscular nerves fibres from MSS patients and from SIL1-deficient mice (woozy) as well as sciatic nerves and neuromuscular junctions (NMJ) from these mice have been investigated via transmission electron microscopic and immunofluorescence studies accompanied by transcript studies and unbiased proteomic profiling. In addition, PNS and NMJ integrity were analyzed via immunofluorescence studies in an MSS-zebrafish model which has been generated for that purpose.

RESULTS

Electron microscopy revealed morphological changes indicative of impaired autophagy and mitochondrial maintenance in distal axons and in Schwann cells. Moreover, changes of the morphology of NMJs as well as of transcripts encoding proteins important for NMJ function were detected in woozy mice. These findings were in line with a grossly abnormal structure of NMJs in SIL1-deficient zebrafish embryos. Proteome profiling of sciatic nerve specimens from woozy mice revealed altered levels of proteins implicated in neuronal maintenance suggesting the activation of compensatory mechanisms.

CONCLUSION

Taken together, our combined data expand the spectrum of tissues affected by SIL1-loss and suggest that impaired neuromuscular transmission might be part of MSS pathophysiology.

Evidence for purine nucleoside phosphorylase (PNP) release from rat C6 glioma cells

Intracellular purine turnover is mainly oriented to preserving the level of triphosphate nucleotides, fundamental molecules in vital cell functions that, when released outside cells, act as receptor signals. Conversely, high levels of purine bases and uric acid are found in the extracellular milieu, even in resting conditions. These compounds could derive from nucleosides/bases that, having escaped to cell reuptake, are metabolized by extracellular enzymes similar to the cytosolic ones. Focusing on purine nucleoside phosphorylase (PNP) that catalyzes the reversible phosphorolysis of purine (deoxy)-nucleosides/bases, we found that it is constitutively released from cultured rat C6 glioma cells into the medium, and has a molecular weight and enzyme activity similar to the cytosolic enzyme. Cell exposure to 10 μM ATP or guanosine triphosphate (GTP) increased the extracellular amount of all corresponding purines without modifying the levels/activity of released PNP, whereas selective activation of ATP P2Y₁ or adenosine A_2A metabotropic receptors increased PNP release and purine base formation. The reduction to 1% in oxygen supply (2 h) to cells decreased the levels of released PNP, leading to an increased presence of extracellular nucleosides and to a reduced formation of xanthine and uric acid. Conversely, 2 h cell re-oxygenation enhanced the extracellular amounts of both PNP and purine bases. Thus, hypoxia and re-oxygenation modulated in opposite manner the PNP release/activity and, thereby, the extracellular formation of purine metabolism end-products. In conclusion, extracellular PNP and likely other enzymes deputed to purine base metabolism are released from cells, contributing to the purinergic system homeostasis and exhibiting an important pathophysiological role.

Inborn errors of metabolism underlying primary immunodeficiencies

A number of inborn errors of metabolism (IEM) have been shown to result in predominantly immunologic phenotypes, manifesting in part as inborn errors of immunity. These phenotypes are mostly caused by defects that affect the (i) quality or quantity of essential structural building blocks (e.g., nucleic acids, and amino acids), (ii) cellular energy economy (e.g., glucose metabolism), (iii) post-translational protein modification (e.g., glycosylation) or (iv) mitochondrial function. Presenting as multisystemic defects, they also affect innate or adaptive immunity, or both, and display various types of immune dysregulation. Specific and potentially curative therapies are available for some of these diseases, whereas targeted treatments capable of inducing clinical remission are available for others. We will herein review the pathogenesis, diagnosis, and treatment of primary immunodeficiencies (PIDs) due to underlying metabolic disorders.

Purine nucleoside phosphorylase deficiency: a mutation update

Purine nucleoside phosphorylase (PNPase) deficiency is an autosomal recessive disorder affecting purine degradation and salvage pathways. Clinically, patients typically present with severe immunodeficiency, neurological dysfunction, and autoimmunity. Biochemically, PNPase deficiency may be suspected in the presence of hypouricemia. We report biochemical and genetic data on a cohort of seven patients from six families identified as PNPase deficient. In all patients, inosine, deoxyinosine, guanosine, and deoxyguanosine were elevated in urine, and mutation analysis revealed seven different mutations of which three were novel. The mutation c.770A>G resulted in the substitution p.His257Arg. A second novel mutation c.257A>G (p.His86Arg) was identified in two siblings and a third novel mutation, c.199C>T (p.Arg67X), was found in a 2-year-old female with delayed motor milestones and recurrent respiratory infections. A review of the literature identified 67 cases of PNPase deficiency from 49 families, including the cases from our own laboratory. PNPase deficiency was confirmed in 30 patients by genotyping and 24 disease causing mutations, including the three novel mutations described in this paper, have been reported to date. In five of the seven patients, plasma uric acid was found to be within the pediatric normal range, suggesting that PNPase deficiency should not be ruled out in the absence of hypouricemia.

Purine nucleoside phosphorylase deficiency with a novel PNP gene mutation: a first case report from India

The authors report a case of purine nucleoside phosphorylase (PNP) deficiency for the first time from India. The case presented with recurrent severe infections, developmental delays, seizures and progressive neurological deterioration. The diagnosis of primary immunodeficiency disorder was delayed in spite of recurrent infection due to predominant neurological symptoms. Sequencing of the PNP gene revealed a novel mutation resulting in a premature stop codon.

Primary immunodeficiency diseases associated with neurologic manifestations

Primary immunodeficiency diseases (PID) are a heterogeneous group of inherited disorders of the immune system, predisposing individuals to recurrent infections, allergy, autoimmunity, and malignancies. A considerable number of these conditions have been found to be also associated with neurologic signs and symptoms. These manifestations are considered core features of some immunodeficiency syndromes, such as ataxia-telangiectasia and purine nucleoside phosphorylase deficiency, or occur less prominently in some others. Diverse pathological mechanisms including defective responses to DNA damage, metabolic errors, and autoimmune phenomena have been associated with neurologic abnormalities; however, several issues remain to be elucidated. Greater awareness of these associated features and gaining a better understanding of the contributing mechanisms will lead to prompt diagnosis and treatment and possibly development of novel preventive and therapeutic strategies. In this review, we aim to provide a brief description of the clinical and genetic characteristics of PID associated with neurologic complications.

Influence of bone marrow stromal microenvironment on forodesine-induced responses in CLL primary cells

Forodesine, a purine nucleoside phosphorylase inhibitor, displays in vitro activity in chronic lymphocytic leukemia (CLL) cells in presence of dGuo, which is the basis for an ongoing clinical trial in patients with fludarabine-refractory CLL. Initial clinical data indicate forodesine has significant activity on circulating CLL cells, but less activity in clearing CLL cells from tissues such as marrow. In tissue microenvironments, lymphocytes interact with accessory stromal cells that provide survival and drug-resistance signals, which may account for residual disease. Therefore, we investigated the impact of marrow stromal cells (MSCs) on forodesine-induced response in CLL lymphocytes. We demonstrate that spontaneous and forodesine-induced apoptosis of CLL cells was significantly inhibited by human and murine MSCs. Forodesine-promoted dGuo triphosphate (dGTP) accumulation and GTP and ATP depletion in CLL cells was inhibited by MSCs, providing a mechanism for resistance. Also, MSCs rescued CLL cells from forodesine-induced RNA- and protein-synthesis inhibition and stabilized and increased Mcl-1 transcript and protein levels. Conversely, MSC viability was not affected by forodesine and dGuo. Collectively, MSC-induced biochemical changes antagonized forodesine-induced CLL cell apoptosis. This provides a biochemical mechanism for MSC-derived resistance to forodesine and emphasizes the need to move toward combinations with agents that interfere with the microenvironment's protective role for improving current therapeutic efforts.

Potent orally bioavailable purine nucleoside phosphorylase inhibitor BCX-4208 induces apoptosis in B- and T-lymphocytes--a novel treatment approach for autoimmune diseases, organ transplantation and hematologic malignancies

The profound suppression of T-cell immunity seen in purine nucleoside phosphorylase (PNP; EC 2.4.2.1) deficient patients supports potential application of inhibitors of PNP in the therapy of T-cell mediated diseases. BCX-4208 is a novel potent transition state analog inhibitor of human PNP with an IC(50) of 0.5 nM. PNP inhibition leads to elevation of dGuo which is converted to dGTP mainly in lymphocytes causing imbalance in deoxynucleotide (dNTP) pools and cell apoptosis. In in vitro studies, neither BCX-4208 nor dGuo alone inhibits proliferation of lymphocytes. BCX-4208 in the presence of 10 microM deoxyguanosine (dGuo) inhibits lymphocyte proliferation induced by MLR, IL-2 or Con A with IC(50)s of 0.159, 0.26 and 0.73 microM, respectively. The IC(50) for dGuo in the presence of 1 microM BCX-4208 for the IL-2 stimulated lymphocytes was 3.12 microM. dGTP in human lymphocytes is elevated and a 3-5 fold increase in dGTP results in 50% inhibition after in vitro exposure to BCX-4208 and dGuo. Flow cytometric analyses of human lymphocytes using annexin V staining reveal that BCX-4208 in the presence of dGuo induces cellular apoptosis in T-cells (CD3+), B-cells (CD20+, CD19+) and NK (CD56+) cells. BCX-4208 is orally bioavailable in mice and elevates plasma dGuo levels to 3.7 microM (predose levels<0.004 microM), similar to levels seen in PNP-deficient patients and levels needed to cause apoptosis in T and B-cells. These data support the evaluation of BCX-4208 in the treatment of T-cell and B-cell mediated diseases. BCX-4208 is currently undergoing early clinical investigation in psoriasis and gout.

A human neuronal tissue culture model for Lesch-Nyhan disease

Mutations in the gene encoding the purine salvage enzyme, hypoxanthine-guanine phosphoribosyltransferase (HPRT) cause Lesch-Nyhan disease, a neurodevelopmental disorder characterized by cognitive, neurological, and behavioral abnormalities. Despite detailed knowledge of the enzyme's function, the key pathophysiological changes that accompany loss of purine recycling are unclear. To facilitate delineating the consequences of HPRT deficiency, four independent HPRT-deficient sublines of the human dopaminergic neuroblastoma, SK-N-BE(2) M17, were isolated by targeted mutagenesis with triple helix-forming oligonucleotides. As a group, these HPRT-deficient cells showed several significant abnormalities: (i) impaired purine recycling with accumulation of hypoxanthine, guanine, and xanthine, (ii) reduced guanylate energy charge and GTP:GDP ratio, but normal adenylate energy charge and no changes in any adenine nucleotide ratios, (iii) increased levels of UTP and NADP+, (iv) reduced DOPA decarboxylase, but normal monoamines, and (v) reduction in cell soma size. These cells combine the analytical power of multiple lines and a human, neuronal origin to provide an important tool to investigate the pathophysiology of HPRT deficiency.

Progressive multifocal leukoencephalopathy in purine nucleoside phosphorylase deficiency

Progressive multifocal leukoencephalopathy is a demyelinating disease caused by JC virus, an opportunistic infection of the central nervous system. Although the majority of cases are infected with the human immunodeficiency virus (HIV), other immunocompromised patients are also at risk. Purine nucleoside phosphorylase is an enzyme in the purine salvage pathway that reversibly converts inosine to hypoxanthine and guanosine to guanine. Purine nucleoside phosphorylase deficiency is a combined immunodeficiency with a profound cellular defect. Neurologic abnormalities are salient features of this syndrome. We describe for the first time a patient with this rare disorder presented with progressive multifocal leukoencephalopathy.

Novel purine nucleoside analogues for T-cell-lineage acute lymphoblastic leukaemia and lymphoma

Purine nucleoside phosphorylase (PNP) deficiency is a rare, inherited immunodeficiency disorder in which the specific molecular defect was identified. Clinically, a lack of PNP manifests as profound T-cell deficiency with minor or variable changes in the humoral system. Biochemically, the absence of PNP results in an increase in plasma deoxyguanosine (dGuo) and a T-cell-specific increase in intracellular deoxyguanosine triphosphate (dGTP). This observation has been the impetus for the search for either inhibitors of the enzyme or PNP-resistant dGuo analogues as potential anti-T-cell-lineage agents over the past 30 years. Forodesine (an inhibitor of PNP) and nelarabine (a PNP-resistant dGuo analogue) proved to be T-cell selective when tested in clinic. This review summarises the preclinical, clinical and pharmacokinetic investigations with these novel agents.

The purine metabolism of human erythrocytes

This review summarizes currently available information about a crucial part of erythrocyte metabolism, that is, purine nucleotide conversions and their relationships with other conversion pathways. We describe the cellular resynthesis, interconversion, and degradation of purine compounds, and also the regulatory mechanisms in the conversion pathways. We also mention purine metabolism disorders and their clinical consequences. The literature is fragmentary because studies have concentrated only on selected aspects of purine metabolism; hence the need for a synthetic approach.

A Golgi study of neuronal architecture in a genetic mouse model for Lesch–Nyhan disease

Lesch-Nyhan disease (LND) is an inherited disorder associated with deficiency of hypoxanthine-guanine phosphoribosyltransferase (HPRT), an enzyme essential for purine recycling. The clinical manifestations of the disorder and several neurochemical studies have pointed towards a defect in the striatum, but histological studies of autopsied brain specimens have not revealed any consistent abnormalities. An HPRT-deficient (HPRT-) mouse that has been produced as a model for the disease also exhibits neurochemical abnormalities of the striatum without obvious histological correlates. In the current studies, Golgi-Cox histochemistry was used to evaluate the fine structure of medium spiny I neurons from the striatum in the HPRT- mice. To determine if any abnormalities might be restricted to striatal neurons, the pyramidal projection neurons of layer 5 of the cerebral cortex were also evaluated. Neurons from both regions demonstrated a normal distribution, orientation, and gross morphology. There was no evidence for an abnormal developmental process or degeneration. However, both regions demonstrated a paucity of neurons with very long dendrites and a reduction in dendritic spines that depended upon the distance from the cell body. These findings demonstrate that HPRT deficiency is associated with changes in neuronal architecture in the HPRT- mice. Similar abnormalities in the LND brain could underlie some of the clinical manifestations.

A proof-of-principle pharmacokinetic, pharmacodynamic, and clinical study with purine nucleoside phosphorylase inhibitor immucillin-H (BCX-1777, forodesine)

The discovery of purine nucleoside phosphorylase (PNP) deficiency and T lymphocytopenia suggested that inhibition of this enzyme could serve as a therapeutic target. Inhibitors of PNP failed until structure-based synthesis of immucillin-H (BCX-1777, forodesine), a transition-state analog of PNP. The picomolar potency for PNP, T cell-selective cytotoxicity, and animal studies provided the rationale for use of forodesine in T-cell malignancies. Five patients were treated with an intravenous infusion of forodesine (40 mg/m2) on day 1; treatment continued on day 2; forodesine was administered every 12 hours for an additional 8 doses. Plasma and cellular pharmacokinetics and pharmaco-dynamics were investigated. Median peak level of forodesine (5.4 microM) was achieved at the end of infusion. This level was sufficient to increase plasma 2'-deoxyguanosine (dGuo) concentrations in all patients. Intracellular deoxyguanosine triphosphate (dGTP) increased by 2- to 40-fold in 4 of 5 patients (8 of 9 courses) and correlated with antileukemia activity in 4 patients. However, objective responses were not observed. This was the first clinical study in humans to demonstrate the plasma pharmacokinetics and the pharmacodynamic effectiveness of the PNP inhibitor, forodesine; however, regrowth of leukemia cells in the blood and marrow after course 1 suggested that a different therapeutic schedule should be considered for future studies.

Purine nucleoside phosphorylase deficiency (PNP-def) presenting with lymphopenia and developmental delay: successful correction with umbilical cord blood transplantation

Purine nucleoside phosphorylase deficiency is a primary immunodeficiency syndrome characterized by the triad of recurrent infection, neurologic dysfunction, and autoimmunity. This patient presented atypically with few infections and normal T-cell function. Progressive lymphopenia, ataxia, and developmental delay led to diagnosis. Umbilical cord blood transplantation corrected the immunodeficiency.

APRT from erythrocytes of HGPRT deficient patients: kinetic, regulatory and thermostability properties

Adenine phosphoribosyltransferase (APRT) has been 1200-fold purified from erythrocytes of a patient with partial hipoxanthine-guanine phosphoribosyltransferase (HGPRT) deficiency, Propositus, and in those of a controlHPRT+, with 20% efficiency in both proteins and specific activity of 550 and 243 nmol/h/mgprotein. The specific activity determined in the Propositus enzyme was, in all purification steps, higher than that of the controlHPRT+. Significant changes were found in their thermal stabilities. Half inactivation times at each temperature studied are greater for the Propositus enzyme in the temperature interval 60-80 degrees C. No significant difference has been observed in the affinity constants for adenine and PRPP substrates. Studies on inhibition by the reaction product suggest that AMP is a competitive inhibitor with respect to PRPP in both enzymes, with Ki values of 150 microM in Propositus and 220 microM in controlHPRT+.

Familial spastic paraplegia as the presenting manifestation in patients with purine nucleoside phosphorylase deficiency

We report two siblings with purine nucleoside phosphorylase deficiency revealed by isolated spastic paraplegia, whereas symptoms of immune deficiency did not become apparent until 3 years of age. As the concurrence of immunodeficiency and neurologic problems strongly suggests the diagnosis of purine nucleoside phosphorylase deficiency, special attention should be paid to counts of lymphocytes in any infant with spastic paraplegia.

Purine nucleoside phosphorylase deficiency: a new case report and identification of two novel mutations (Gly156A1a and Val217Ile), only one of which (Gly156A1a) is deleterious

Purine nucleoside phosphorylase (PNP) deficiency results in an autosomal recessive immunodeficiency disease characterized by initial involvement of cellular immunity and neurological manifestations with subsequent abnormalities of humoral immunity. The initial presentation and clinical course has varied widely in the relatively few published cases. The molecular basis has been reported in only 10 patients, precluding evaluation of phenotype-genotype relationships. We now report clinical, immunologic, and molecular findings in a new case of relatively early onset that emphasizes hypotonia and developmental delay as early manifestations. The patient carried two novel missense mutations (Gly56A1a and Val217Ile) on the same allele in apparent homozygosity. Expression of each of the mutant enzymes in vitro demonstrated that the Gly156A1a mutation abolished enzyme activity while the Val217Ile mutation was without obvious effect and is therefore a normal variant. Such "normal" polymorphisms might be associated with a variable response to the immunosuppressive PNP inhibitors currently in clinical trials.

Development of transition state analogues of purine nucleoside phosphorylase as anti-T-cell agents

Newborns with a genetic deficiency of purine nucleoside phosphorylase (PNP) are normal, but exhibit a specific T-cell immunodeficiency during the first years of development. All other cell and organ systems remain functional. The biological significance of human PNP is degradation of deoxyguanosine, and apoptosis of T-cells occurs as a consequence of the accumulation of deoxyguanosine in the circulation, and dGTP in the cells. Control of T-cell proliferation is desirable in T-cell cancers, autoimmune diseases, and tissue transplant rejection. The search for powerful inhibitors of PNP as anti-T-cell agents has culminated in the immucillins. These inhibitors have been developed from knowledge of the transition state structure for the reactions catalyzed by PNP, and inhibit with picomolar dissociation constants. Immucillin-H (Imm-H) causes deoxyguanosine-dependent apoptosis of rapidly dividing human T-cells, but not other cell types. Human T-cell leukemia cells, and stimulated normal T-cells are both highly sensitive to the combination of Imm-H to block PNP and deoxyguanosine. Deoxyguanosine is the cytotoxin, and Imm-H alone has low toxicity. Single doses of Imm-H to mice cause accumulation of deoxyguanosine in the blood, and its administration prolongs the life of immunodeficient mice in a human T-cell tissue xenograft model. Immucillins are capable of providing complete control of in vivo PNP levels and hold promise for treatment of proliferative T-cell disorders.

Purine nucleoside phosphorylase inhibitor BCX-1777 (Immucillin-H)--a novel potent and orally active immunosuppressive agent

Patients with purine nucleoside phosphorylase (PNP) deficiency present a selective T-cell immunodeficiency. Inhibitors of PNP are, therefore, of interest as potential T-cell selective immunosuppressive agents. BCX-1777 is a potent inhibitor of PNP from various species including human, mouse, rat, monkey and dog, with IC50 values ranging from 0.48 to 1.57 nM. BCX-1777, in the presence of 2'-deoxyguanosine (dGuo, 3-10 microM), inhibits human lymphocyte proliferation activated by various agents such as interleukin-2 (IL-2), mixed lymphocyte reaction (MLR) and phytohemagglutinin (PHA) (IC50 values < 0.1-0.38 microM). BCX-1777 is a 10-100-fold more potent inhibitor of human lymphocyte proliferation than other known PNP inhibitors like PD141955 and BCX-34. Nucleotide analysis of human lymphocytes indicate that inhibition of proliferation by BCX-1777 correlates with dGTP levels in the cells. BCX-1777 has excellent oral bioavailability (63%) in mice. At a single dose of 10 mg/kg in mice, BCX-1777 elevates dGuo to approximately 5 microM. BCX-1777 was not effective in mouse T-cell models such as delayed type hypersensitivity (DTH) and splenomegaly because mouse T-cells do not accumulate dGTP as do human T-cells. However, in the human peripheral blood lymphocyte severe combined immunodeficiency (hu-PBL-SCID) mouse model, BCX-1777 was effective in prolonging the life span 2-fold or more. This is the first known example of a PNP inhibitor that elevates dGuo in mice similar to the levels observed in PNP-deficient patients. Furthermore, these dGuo levels are also required for in vitro T-cell inhibition by BCX-1777. Thus, BCX-1777 represents a novel class of selective immunosuppressive agents that could have therapeutic utility in various T-cell disorders.

Involvement of astrocytes in purine‐mediated reparative processes in the brain

Astrocytes are involved in multiple brain functions in physiological conditions, participating in neuronal development, synaptic activity and homeostatic control of the extracellular environment. They also actively participate in the processes triggered by brain injuries, aimed at limiting and repairing brain damages. Purines may play a significant role in the pathophysiology of numerous acute and chronic disorders of the central nervous system (CNS). Astrocytes are the main source of cerebral purines. They release either adenine-based purines, e.g. adenosine and adenosine triphosphate, or guanine-based purines, e.g. guanosine and guanosine triphosphate, in physiological conditions and release even more of these purines in pathological conditions. Astrocytes express several receptor subtypes of P1 and P2 types for adenine-based purines. Receptors for guanine-based purines are being characterised. Specific ecto-enzymes such as nucleotidases, adenosine deaminase and, likely, purine nucleoside phosphorylase, metabolise both adenine- and guanine-based purines after release from astrocytes. This regulates the effects of nucleotides and nucleosides by reducing their interaction with specific membrane binding sites. Adenine-based nucleotides stimulate astrocyte proliferation by a P2-mediated increase in intracellular [Ca2+] and isoprenylated proteins. Adenosine also, via A2 receptors, may stimulate astrocyte proliferation, but mostly, via A1 and/or A3 receptors, inhibits astrocyte proliferation, thus controlling the excessive reactive astrogliosis triggered by P2 receptors. The activation of A1 receptors also stimulates astrocytes to produce trophic factors, such as nerve growth factor, S100beta protein and transforming growth factor beta, which contribute to protect neurons against injuries. Guanosine stimulates the output of adenine-based purines from astrocytes and in addition it directly triggers these cells to proliferate and to produce large amount of neuroprotective factors. These data indicate that adenine- and guanine-based purines released in large amounts from injured or dying cells of CNS may act as signals to initiate brain repair mechanisms widely involving astrocytes.

Mitochondrial basis for immune deficiency. Evidence from purine nucleoside phosphorylase-deficient mice

We generated purine nucleoside phosphorylase (PNP)-deficient mice to gain insight into the mechanism of immune deficiency disease associated with PNP deficiency in humans. Similar to the human disease, PNP deficiency in mice causes an immunodeficiency that affects T lymphocytes more severely than B lymphocytes. PNP knockout mice exhibit impaired thymocyte differentiation, reduced mitogenic and allogeneic responses, and decreased numbers of maturing thymocytes and peripheral T cells. T lymphocytes of PNP-deficient mice exhibit increased apoptosis in vivo and higher sensitivity to gamma irradiation in vitro. We propose that the immune deficiency in PNP deficiency is a result of inhibition of mitochondrial DNA repair due to the accumulation of dGTP in the mitochondria. The end result is increased sensitivity of T cells to spontaneous mitochondrial DNA damage, leading to T cell depletion by apoptosis.

A twenty strain survey and backcross localization of the erythrocytic GTP concentration determining locus Gtpc on mouse chromosome 9

Erythrocyte nucleotide concentrations were surveyed among 20 inbred strains of mice in order to further assess the variability in GTP concentration. There was no significant difference in erythrocytic ATP concentration (Scheffé's test at P = 0.01), 678-1154 nmol/mL packed cells, among the strains surveyed. Two groups were distinguishable with respect to erythrocytic GTP concentration, 8 strains having high GTP, 215 +/- 44 nmole/mL packed cells, and 12 strains having low GTP, 34 +/- 12 nmole/mL packed cells. The erythrocytic GTP concentration determining trait Gtpc was previously shown to be linked to transferrin, Trf, on chromosome 9. Analysis of 232 [(B6 x WB) F1 x B6] backcross individuals for Gtpc and 8 microsatellite markers restricted the localization of Gtpc to a 5.6 +/- 2.1 cM region. The gene order and genetic distances in cM +/- SE are: (D9Mit14) 0.4 +/- 0.4 (D9Mit24) 1.7 +/- 0.8 (Gtpc, D9Mit51, D9Mit116, D9Mit212) 3.9 +/- 1.3 (D9Mit200) 3.0 +/- 1.1 (D9Mit20) 7.8 +/- 1.8 (D9Mit18). The GTP concentration determining trait appears to be a property of erythrocytes as no differences were observed for GTP/ATP ratios of brain, kidney, liver, and tongue from a low GTP strain, C3H/HeHa x Pgk-la and a high GTP strain, C57BL/6J.

Abnormal purine and pyrimidine nucleotide content in primary astroglia cultures from hypoxanthine-guanine phosphoribosyltransferase-deficient transgenic mice

Lesch-Nyhan syndrome is a pediatric metabolic-neurological syndrome caused by the X-linked deficiency of the purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT). The cause of the metabolic consequences of HGPRT deficiency has been clarified, but the connection between the enzyme deficiency and the neurological manifestations is still unknown. In search for this connection, in the present study, we characterized purine nucleotide metabolism in primary astroglia cultures from HGPRT-deficient transgenic mice. The HGPRT-deficient astroglia exhibited the basic abnormalities in purine metabolism reported before in neurons and various other HGPRT-deficient cells. The following abnormalities were found: absence of detectable uptake of guanine and of hypoxanthine into intact cell nucleotides; 27.8% increase in the availability of 5-phosphoribosyl-1-pyrophosphate; 9.4-fold acceleration of the rate of de novo nucleotide synthesis; manyfold increase in the excretion into the culture media of hypoxanthine (but normal excretion of xanthine); enhanced loss of label from prelabeled adenine nucleotides (loss of 71% in 24 h, in comparison with 52.7% in the normal cells), due to 4.2-fold greater excretion into the media of labeled hypoxanthine. In addition, the HGPRT-deficient astroglia were shown to contain lower cellular levels of ADP, ATP, and GTP, indicating that the accelerated de novo purine synthesis does not compensate adequately for the deficiency of salvage nucleotide synthesis, and higher level of UTP, probably due to enhanced de novo synthesis of pyrimidine nucleotides. Altered nucleotide content in the brain may have a role in the pathogenesis of the neurological deficit in Lesch-Nyhan syndrome.

Point mutations at the purine nucleoside phosphorylase locus impair thymocyte differentiation in the mouse

Three point mutations on the Np(b) allele of the purine nucleoside phosphorylase locus in the mouse have been recovered by male germ cell mutagenesis. The mutants were backcrossed, 12-14 generations, and are designated in increasing order of severity of enzyme deficiency and phenotype: B6-NPE, Met-87 --> Lys; B6-NPF, Ala-228 --> Thr; and B6-NPG, Trp-16 --> Arg. A marked decline in total cell numbers per thymus occurs between 2 and 3 months for the more severe B6-NPF and B6-NPG mutants (35% and 52%, respectively) and by 8 months for the less severe B6-NPE mutation. The thymocyte population is thereafter characterized by a 3- or 8-fold expanded precursor, CD4-CD8- double-negative population and 15% or 55% reduced CD4+CD8+ double-positive cells for the B6-NPF and B6-NPG strains, respectively. Spleen lymphocyte Thy-1+ cells are reduced by 50% and spleen lymphocyte response to T cell mitogen and interleukin 2 is reduced by 80%. Increases of thymocyte dGTP pools of 5- and 2.5-fold for B6-NPF and B6-NPG mutants, respectively, are observed. The purine nucleoside phosphorylase-deficient mouse exhibits age-dependent progressive perturbations in thymocyte differentiation, reduced numbers of thymocytes, and reduced splenic T cell numbers and response. The progressive T cell deficit is similar to the human disorder.

In vivo and in vitro pharmacologic activity of the purine nucleoside phosphorylase inhibitor BCX-34: the role of GTP and dGTP

BCX-34 inhibits RBC PNP in vitro from humans, rats, and mice with IC50S ranging from 5 to 36 nM. BCX-34 also, in the presence but not in the absence of deoxyguanosine, inhibits human CCRF-CEM T-cell proliferation with an IC50 of 0.57 microM but not rat or mouse T-cell proliferation up to 30 microM. Inhibition of human T-cell proliferation is accompanied by an accumulation of intracellular dGTP with an associated reduction in GTP. These nucleotide changes do not occur in BC16A mouse T-cells and explain why proliferation is not inhibited by PNP inhibitors in this case. Reduction in intracellular GTP is not essential for the antiproliferative action of BCX-34. Oral bioavailability of BCX-34 in rats is 76%. BCX-34 is orally active in elevating plasma inosine in rats (2-fold at 30 mg/kg), in suppressing ex vivo RBC PNP activity in rats (98% at 3 h. 100 mg/kg), and in suppressing ex vivo skin PNP in mice (39% at 3 h, 100 mg/kg). The results demonstrate that BCX-34 inhibits human PNP and T-cell proliferation, is orally bioavailable in rodents, and pharmacologically active in vivo in rodents after oral dosing with no apparent side effects or toxicity. BCX-34 may, therefore, be useful in treating human T-cell proliferative inflammatory disorders.

Correction of purine nucleoside phosphorylase deficiency by transplantation of allogeneic bone marrow from a sibling

Deficiency of the purine salvage pathway enzyme purine nucleoside phosphorylase causes a combined immunodeficiency and neurologic abnormalities and is usually fatal in childhood. We report the first successful transplantation of bone marrow from a sibling with identical class II human leukocyte antigens in this condition, demonstrating correction of both lymphocyte metabolic and functional abnormalities.

Adenine nucleotide metabolism in primary rat neuronal cultures

The metabolism of adenine nucleotides (AdRN) has been studied previously in whole brains, brain slices and brain extracts, containing mixed populations of neurons and glia. The availability of primary neuronal cultures enables us to study these pathways in almost pure neuronal preparations. The aim of the present study was to characterize the relative importance of the pathways of AdRN metabolism in the neurons. The metabolic fate of (8-14C) adenine and of AdRN prelabeled with (8-14C)adenine were studied in immature and mature primary rat neuronal cultures. Specific inhibitors were used to clarify the various metabolic fluxes, which were evaluated based on the time-related changes in the distribution of label (the cellular nucleotide content did not change during incubation). The turnover rate of AdRN was found to reflect mainly conversion of label to acid insoluble derivatives (AID) and partly degradation to hypoxanthine. The turnover was faster in the immature neurons. The combined addition of 2'-deoxycoformycin (2'-dCF) and of 5'-amino-5'-deoxyadenosine, inhibiting adenosine metabolism, resulted in both cultures in enhanced loss of label from AdRN, mainly to adenosine and adenine. This finding indicates the activity of the futile cycle AMP-->adenosine-->AMP. In both cultures, in the presence of these inhibitors, the ratio (hypoxanthine + inosine)/(adenine + adenosine) was 1.1, indicating that the fluxes through AMP deamination and AMP dephosphorylation are about equal. Addition of L-alanosine, inhibiting the conversion of IMP to AMP, resulted in both cultures, but especially in the mature neurons, in enhanced loss of label from AdRN to hypoxanthine and inosine. This finding indicates the functioning of the adenine nucleotide cycle (AMP-->IMP-->adenylosuccinic acid-->AMP). Under conditions of enhanced degradation of ATP (induced by iodoacetate and antimycin A), addition of 2'-dCF resulted in the immature cultures in lowering the ratio (hypoxanthine + inosine + IMP)/(adenine + adenosine) to 0.62, indicating a shift in favor of AMP dephosphorylation.

Developmental changes in purine nucleotide metabolism in cultured rat astroglia

The present study was conducted in order to clarify the role of the glia in brain purine metabolism. This, in connection with the clarification of the etiology of the neurological manifestations associated with some of the inborn errors of purine metabolism in man. Purine nucleotide content, the capacity for de novo and salvage purine synthesis and the activity of several enzymes of purine nucleotide degradation, were assayed in primary cultures of rat astroglia in relation to culture age. The capacity of the intact cells to produce purine nucleotides de novo exhibited a marked decrease with the culture age, but the activity of hypoxanthine-guanine phosphoribosyltransferase (HGPRT), catalyzing salvage nucleotide synthesis, increased. Aging was also associated with a marked increase in the activity of the degradation enzymes AMP deaminase, purine nucleoside phosphorylase (PNP) and guanine deaminase (guanase). The activity of adenosine deaminase and of AMP-5'-nucleotidase, increased markedly during the first 17 days in culture, but decreased thereafter. The results indicate that purine nucleotide metabolism in the cultured astroglia is changing with aging to allow the cells to maintain their nucleotide pool by reutilization of preformed hypoxanthine, rather than by de-novo production of new purines. Aging is also associated with increased capacity for operation of the adenine nucleotide cycle, contributing to the homeostasis of adenine nucleotides and to the energy charge of the cells. In principle, the age-related alterations in purine metabolism in the astroglia resemble those occurring in the maturating neurons, except for the capacity to produce purines de novo, which exhibited inverse trends in the two tissues. However, in comparison to the neurons, the cultured astroglia possess the capacity for a more intensive metabolism of purine nucleotides.

Stroke in purine nucleoside phosphorylase deficiency

The first documented case of cerebrovascular disease occurring in a 13-year-old girl with purine nucleoside phosphorylase deficiency is reported. This patient, the oldest known survivor with purine nucleoside phosphorylase deficiency, had previously experienced multiple sequential neurologic problems. She presented with episodes of transient left hemiparesis, followed shortly thereafter by dense left hemiplegia. Magnetic resonance imaging revealed a right internal capsule infarct; cerebral angiography revealed vasculopathy of the proximal vessels. Proposed mechanisms for neurologic dysfunction and cerebrovascular disease in purine nucleoside phosphorylase deficiency are discussed.

Secondary loss of deoxyguanosine kinase activity in purine nucleoside phosphorylase deficient mice

The T-cell immunodeficiency associated with purine nucleoside phosphorylase (PNP) deficiency in man is believed to be due to the accumulation of dGTP which may be preferentially formed from deoxyguanosine in T-lymphocytes or their precursor cells. We found no evidence for dGTP accumulation in thymocytes or spleen leucocytes, < 1 nmol/10(9) cells, nor in erythrocytes, < 0.05 nmol/10(9) cells, of the B6-NPE- or B6-NPF PNP-deficient mice strains. There were no changes in purine or pyrimidine ribonucleotide pools. As these mice had been previously shown to excrete PNP nucleoside substrates, we examined the metabolism of deoxyguanosine. Deoxyguanosine kinase activity as compared to control mice was 6 to 52% for the B6-NPE mutant, 2 to 22% for the B6-NPF mutant. Fractionation of erythrocyte and liver lysates from the F mutation and the background strain, C57BL/6J, by anion exchange chromatography confirmed the secondary deficiency of deoxyguanosine kinase and demonstrated that this activity was distinct from adenosine kinase and two major peaks of deoxycytidine kinase activity. Mouse PNP, expressed and purified as a fusion protein, did not show evidence of being bifunctional and having deoxyguanosine kinase activity. Metabolic modelling revealed that the ratio of deoxyguanosine phosphorylation versus phosphorolysis was < 0.06 in control mice, and < or = 0.3 in lymphocytes of PNP-deficient mice. Were deoxyguanosine kinase not reduced in the PNP-deficient mice, all tissues of the B6-NPF mutant would preferentially phosphorylate deoxyguanosine at low substrate concentrations.

Differences in purine metabolism in patients with Down's syndrome

Three enzymes intervening in de novo purine synthesis, as well as cystathionine B-synthetase, have been mapped to chromosome 21. In order to gain a better understanding of purine synthesis anomalies in Down's syndrome, the present authors studied the variations in mitotic index of lymphocyte cultures to which various inhibitors or metabolites of purine synthesis had been added. In spite of common gene dosage effects, unexpected and highly significant differences were noted between Down's syndrome patients without complications and those presenting with additional psychotic features. In Down's syndrome patients without complications, a highly significant decrease in mitotic index was noted in the presence of exogenous inosine. A significant decrease in the presence of adenosine and guanosine was also noted. These findings are in keeping with the expected metabolic repercussions of genes mapped to chromosome 21. In Down's syndrome patients with psychotic complications, the in vitro reactions were quite different. A paradoxal increase in mitotic index was noted in the presence of inosine and of adenosine, but the response to guanosine did not differ from that observed in normal controls. These findings were unexpected and seem to indicate that, in spite of the gene dosage effect, psychotic Down's syndrome patients are unable to compensate abnormal purine synthesis and resulting imbalances. Furthermore, a marked difference in purine metabolic reactions was noted between Down's syndrome patients receiving supplemental folic/folinic acid and those on no therapy. This suggests that some modulation of the gene dosage effect may be possible.

Characterization of the alterations in purine nucleotide metabolism in hypoxanthine-guanine phosphoribosyltransferase-deficient rat neuroma cell line

A rat neuroma cell line (B103 4C), deficient of hypoxanthine-guanine phosphoribosyltransferase (HGPRT), was utilized as a model tissue in search for the biochemical basis of the Lesch-Nyhan syndrome (LNS). The HGPRT-deficient neurons exhibited the following properties: an almost complete absence of uptake of guanine and of hypoxanthine into intact cell nucleotides (0.92% and 0.69% of normal, respectively); a significant increase in the availability of 5'-phosphoribosyl-1-pyrophosphate; a three- to fourfold acceleration of the rate of de novo nucleotide synthesis; a normal excretion of xanthine, but 15-fold increase in the excretion of hypoxanthine into the culture media; a normal cellular purine nucleotide content, including the absence of 5-amino-4-imidazole carboxamide nucleotides (Z-nucleotides), but enhanced turnover of adenine nucleotides (loss of 86% of the radioactivity of the prelabeled pool in 24 h, in comparison to 73% in the normal line), and an elevated UTP content. The results suggest that, under physiological conditions, guanine salvage does not occur in the normal neurons, but that hypoxanthine salvage is of great importance in the homeostasis of the adenine nucleotide pool. The finding of the normal profile of purine nucleotides in the HGPRT-deficient neurons indicates that the lack of hypoxanthine salvage is adequately compensated by the enhanced de novo nucleotide synthesis. These results did not furnish evidence in support of the possibility that GTP or ATP depletion, or Z-nucleotide accumulation, occurs in HGPRT-deficient neurons and that these are etiological factors causing the neurological abnormalities in LNS.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolism of guanine and guanine nucleotides in primary rat neuronal cultures

The metabolic fate of guanine and of guanine ribonucleotides (GuRNs) in cultured rat neurons was studied using labeled guanine. 8-Aminoguanosine (8-AGuo), an inhibitor of purine nucleoside phosphorylase, was used to clarify the pathways of GMP degradation, and mycophenolic acid, an inhibitor of IMP dehydrogenase, was used to assess the flux from IMP to GMP and, indirectly, the activity of the guanine nucleotide cycle (GMP----IMP----XMP----GMP). The main metabolic fate of guanine in the neurons was deamination to xanthine, but significant incorporation of guanine into GuRNs, at a rate of approximately 8.5-13.1% of that of the deamination, was also demonstrated. The turnover rate of GuRNs was fast (loss of 80% of the radioactivity of the prelabeled pool in 22 h), reflecting synthesis of nucleic acids (32.8% of the loss in radioactivity) and degradation to xanthine, guanine, hypoxanthine, guanosine, and inosine (49.3, 4.3, 4.1, 1.1, and 0.5% of the loss, respectively). Of the radioactivity in GuRNs, 7.9% was shifted to adenine nucleotides. The accumulation of label in xanthine indicates (in the absence of xanthine oxidase) that the main degradative pathway from GMP is that to xanthine through guanosine and guanine. The use of 8-AGuo confirmed this pathway but indicated the operation of an additional, relatively slower degradative pathway, that from GMP through IMP to inosine and hypoxanthine. Hypoxanthine was incorporated mainly into adenine nucleotide (91.5%), but a significant proportion (6%) was found in GuRNs.(ABSTRACT TRUNCATED AT 250 WORDS)

Dysequilibrium/ataxic diplegia with immunodeficiency

A girl with purine nucleoside phosphorylase (PNP) deficiency is described. The nature of the motor disorder is similar to other children since found to have PNP deficiency. It is suggested that the diagnosis be considered in any child with unexplained dysequilibrium/ataxic diplegia. Other previously unreported features are intracytoplasmic neutrophil inclusion bodies and an improvement in the neutropenia after intravenous immunoglobulin.