Serum granulocyte colony-stimulating factor levels are not increased in patients with autoimmune neutropenia of infancy

Milestones in understanding platelet production: a historical overview

The discovery of thrombopoietin (TPO, also termed THPO) in 1994 was a major achievement in understanding the regulation of platelet production. In prior decades, physiological studies had demonstrated that platelets were produced from bone marrow megakaryocytes and that the megakaryocytes responded to thrombocytopenia by increasing their number, size and DNA ploidy. In 1958, it was proposed that a 'thrombopoietin' must exist that regulated this interaction between the circulating platelet mass and the bone marrow megakaryocytes. After over three decades of effort, TPO was finally purified by five independent laboratories. TPO stimulated megakaryocyte colony-forming cell growth and increased the number, size and ploidy of megakaryocytes. When the genes for TPO or TPO receptor were eliminated in mice, megakaryocytes grew and platelets were made, but at 15% of their normal number. A first generation of recombinant human (rh) TPO molecules [rhTPO and pegylated recombinant human megakaryocyte growth and development factor (PEG-rhMGDF)] rapidly entered clinical trials in 1995 and increased platelet counts in humans undergoing non-myeloablative chemotherapy but not in those undergoing stem cell transplantation. Antibodies developed against PEG-rhMGDF and development of these recombinant thrombopoietins ended. A second generation of TPO receptor agonists (romiplostim and eltrombopag) was then developed. Neither of these TPO receptor agonists demonstrated any significant untoward effects and both are now licensed in many countries for the treatment of immune thrombocytopenia. This review describes the significant experiments that have surrounded the discovery of TPO and its clinical development.

Prospective screening of 205 patients with ITP, including diagnosis, serological markers, and the relationship between platelet counts, endogenous thrombopoietin, and circulating antithrombopoietin antibodies

Immune thrombocytopenia purpura (ITP) is characterized by destruction of circulating platelets and the presence of antiplatelet antibodies. Many of the current immunomodulatory therapies act by reducing platelet destruction and usually do not have a lasting effect. This prospective, exploratory study characterized patients with ITP by identifying their demographic and comorbid clinical factors, use of treatments, serologic markers of autoimmunity, and possible relationships between platelet counts, concentrations of endogenous thrombopoietin (eTPO), and the presence of circulating anti-TPO antibodies. Data including medical history and laboratory evaluations were collected at a single patient visit on 205 patients (19 children, 186 adults). Reported histories revealed a 5% rate of thrombotic/ischemic events. Autoimmune markers including direct antiglobulin test and antinuclear antibodies were found more frequently than in the normal population; antiplatelet antibody testing was not done. eTPO concentrations were comparable to concentrations found in healthy volunteers. Our study confirmed that no significant inverse correlation occurred between circulating concentrations of eTPO and platelet counts in patients with ITP (Spearman r = -0.15). Two of the 205 patients tested (1%) had neutralizing activity of recombinant human TPO in a biological assay; however, this activity was confirmed to be anti-TPO antibody in only 1 patient.

[HHV 8 positive Castleman's disease and auto-immune neutropenia in 2 HIV-infected patients]

INTRODUCTION

Castleman's disease (CD) is a polyclonal lymphoplasmacytic and vascular proliferation prominent in lymphoid tissues, associated to Human Herpesvirus 8 (HHV-8) in Human Immunodeficiency Virus (HIV)-infected patients. The presence of autoimmune stigmates is frequent.

EXEGESIS

We report two cases of neutropenia secondary to IgG neutrophil autoantibodies, indeterminate specificity, occurring in two HIV-infected patients with CD HHV-8+, treated by vinblastine since several years. The neutropenia was associated to other biologic stigmates of autoimmunity and the evolution has been complicated by several infections. Granulocyte-colony stimulating factor (G-CSF) and polyvalent immunoglobulin permitted a transient and low increase of neutrophila in one case.

CONCLUSION

Auto-immune neutropenia in CD is rare and difficult to treat in our cases. This evolution is independent of relapse of CD. The immunoglobulin and G-CSF may be transitory effective.

Effect of recombinant granulocyte colony-stimulating factor on blood neutrophil concentrations among patients with "idiopathic neonatal neutropenia": a randomized, placebo-controlled trial

OBJECTIVES

We previously described a severe, prolonged, idiopathic, but self-resolving, variety of neutropenia among preterm neonates. In the present study, we sought to assess the marrow neutrophil reserves of these patients by serially measuring blood neutrophils following the administration of recombinant granulocyte colony-stimulating factor (rG-CSF) or placebo.

STUDY DESIGN

Prospective, randomized trial of rG-CSF vs placebo for infants with "idiopathic neonatal neutropenia".

RESULTS

During 36 consecutive months, 2407 neonates were admitted to the neonatal intensive care unit; 429 weighed less than 1500 g at birth, 14 of these were later diagnosed with "idiopathic neonatal neutropenia"; 10 were enrolled in this trial. The five rG-CSF recipients had an immediate, marked increase in blood neutrophil concentration, indicating adequate rG-CSF-mobilizable marrow neutrophil reserves. This effect persisted to day 5, but counts were not different from those of the five placebo recipients on days 12 and 15.

CONCLUSIONS

Patients with "idiopathic neonatal neutropenia" have a substantial rG-CSF-mobilizable marrow neutrophil reserve. On that basis, we speculate that this variety of neonatal neutropenia does not constitute a significant deficiency in antibacterial defense.

Psychosocial adaptation to short stature - an indication for growth hormone therapy?

Although growth hormone does not clearly improve final height in non-growth-hormone-deficient children with short stature, it leads to a temporary acceleration of growth velocity. It is an ongoing discussion whether this effect supports psychosocial adaptation to short stature and therefore could be an indication for growth hormone treatment in children with short stature without growth hormone deficiency. We have reviewed recent literature concerning psychosocial consequences of short stature. Together with own data we can demonstrate that short people regularly adapt well to their height and have a good self-esteem. On the other hand, we focus on the problem that most studies on this subject suffer from methodical problems. A growth-related questionnaire that evaluates subjective and objective perceptions of being short in patients and peers is not at hand. As a consequence, psychosocial problems due to short stature have not been exactly classified yet and therefore do not represent an indication for growth hormone therapy.

Immune-mediated neutropenia in the neonate

Alloimmune neonatal neutropenia, neonatal autoimmune neutropenia and autoimmune neutropenia of infancy have remained nebulous entities with difficulties in both clinical and laboratory identification. These disorders are reviewed in this article.

The use of granulocyte colony-stimulating factor for treatment of autoimmune neutropenia

The advent of better diagnostic tools, molecular techniques, and cytokine therapies have come together at the end of the 20th century to provide an improved outlook for patients with autoimmune neutropenia. Severe chronic neutropenia is no longer idiopathic in most cases, and growth factor therapy can be safely offered to selected patient groups. Previously unsuccessful and even dangerous forms of treatment are no longer appropriate, and G-CSF treatment appears to be safe when administered long term. Fears about transformation of these disorders into acute myeloblastic leukemia probably relate to the underlying natural history of these disorders rather than to their treatment.