Identification of new Fas mutations in a patient with autoimmune lymphoproliferative syndrome (ALPS) and eosinophilia

Autoimmune lymphoproliferative syndrome (ALPS) is a rare, newly recognized, chronic lymphoproliferative disorder in children and is characterized by lymphadenopathy, splenomegaly, pancytopenia, autoimmune phenomena and expansion of double-negative (DN) T lymphocytes (TCR alpha beta+, CD4-, CD8-). Defective lymphocyte apoptosis caused by mutations of the Fas (CD95) gene has been linked in the pathogenesis of ALPS, as binding of Fas-ligand to Fas can trigger apoptosis. Of the ALPS cases reported to date, point mutations, frameshifts and silent mutations in Fas all have been identified. We report two new point mutations in Fas in a child with ALPS and eosinophilia; studies on other family members established the pattern of inheritance for these mutations. Flow cytometric analysis of blood and tissues (spleen, lymph node, bone marrow) revealed abnormally expanded populations of DN T lymphocytes. Furthermore, activated lymphocytes and IFN gamma-activated eosinophils were resistant to Fas-mediated apoptosis. Eosinophil resistance to Fas-mediated apoptosis has not been previously described in ALPS. Sequencing of Fas revealed two separate mutations not previously reported. One mutation, a C to T change at base 836, was a silent mutation inherited from the mother, while the second mutation, a C to A change at base 916, caused a non-conservative amino acid substitution in the death domain of Fas, changing a threonine to a lysine. This mutation is associated with a predicted change in the structure of a part of the death domain from a beta-pleated sheet to an alpha-helix. We speculate that the mutation in the death domain prevents the interaction of Fas with intracellular mediators of apoptosis and is responsible for the autoimmune manifestations of ALPS and the abnormal lymphocytosis and eosinophilia in this patient.     

The development of lymphomas in families with autoimmune lymphoproliferative syndrome with germline Fas mutations and defective lymphocyte apoptosis.

Lymphomas were studied in kindreds with autoimmune lymphoproliferative syndrome (ALPS; Canale-Smith syndrome), a disorder of lymphocyte homeostasis usually associated with germline Fas mutations. Fas (CD95/APO-1) is a cell surface receptor that initiates programmed cell death, or apoptosis, of activated lymphocytes. Lymphoma phenotype was determined by immunohistochemistry, frequency of CD3(+)CD4(-)CD8(-) T-cell-receptor alpha/beta cells by flow cytometry, nucleotide sequences of the gene encoding Fas (APT1, TNFRSF6), and the percentage of lymphocytes undergoing apoptosis in vitro. Of 223 members of 39 families, 130 individuals possessed heterozygous germline Fas mutations. Eleven B-cell and T-cell lymphomas of diverse types developed in 10 individuals with mutations in 8 families, up to 48 years after lymphoproliferation was first documented. Their risk of non-Hodgkin and Hodgkin lymphomas, respectively, was 14 and 51 times greater than expected (each P <.001). Investigation of these 10 patients and their relatives with Fas mutations revealed that all had defective lymphocyte apoptosis and most had other features of ALPS. The tumor cells retained the heterozygous Fas mutations found in the peripheral blood and manifested defective Fas-mediated killing. These data implicate a role for Fas-mediated apoptosis in preventing B-cell and T-cell lymphomas. Inherited defects in receptor-mediated lymphocyte apoptosis represent a newly appreciated risk factor for lymphomas.     

Diffuse large B-cell non-Hodgkin's lymphoma in a patient with autoimmune lymphoproliferative syndrome

Mutations of Fas or Fas ligand genes result in the autoimmune lymphoproliferative syndrome (ALPS) in humans. We report here a diffuse large B-cell non-Hodgkin's lymphoma occurring in a man with ALPS. Fas-mediated lymphocyte apoptosis was defective in vitro, owing to a mutation within the death domain of the Fas molecule. High-dose methotrexate and doxorubicin-based chemotherapy led to complete remission of lymphoma.     

Perforin-dependent apoptosis functionally compensates Fas deficiency in activation-induced cell death of human T lymphocytes

Activation-induced cell death (AICD) is involved in peripheral tolerance by controlling the expansion of repeatedly stimulated T cells via an apoptotic Fas (CD95; APO-1)-dependent pathway. The TNFRSF-6 gene encoding Fas is mutated in children suffering from autoimmune lymphoproliferative syndrome (ALPS), which is characterized by lymphoproliferation and autoimmunity. We examined AICD in Fas-deficient T cells from ALPS patients. We showed that primary activated Fas-deficient T cells die by apoptosis after repeated T cell antigen receptor (TCR) stimulation despite resistance to Fas-mediated cell death. This Fas-independent AICD was found to be mediated through a cytotoxic granules-dependent pathway. Cytotoxic granules-mediated AICD was also detected in normal T lymphocytes though to a lesser extent. As expected, the cytotoxic granules-dependent AICD was abolished in T cells from Rab27a- or perforin-deficient patients who exhibited defective granules-dependent cytotoxicity. Supporting an in vivo relevance of the cytotoxic granules-dependent AICD in ALPS patients, we detected an increased number of circulating T lymphocytes expressing granzymes A and B. Altogether, these data indicated that the cytotoxic granules-dependent cell death in ALPS may compensate for Fas deficiency in T lymphocytes. Furthermore, they identified a novel AICD pathway as a unique alternative to Fas apoptosis in human peripheral T lymphocytes.     

Defective CD95/APO-1/Fas signal complex formation in the human autoimmune lymphoproliferative syndrome, type Ia

Heterozygous mutations in the CD95 (APO-1/Fas) receptor occur in most individuals with autoimmune lymphoproliferative syndrome (ALPS) and dominantly interfere with apoptosis by an unknown mechanism. We show that local or global alterations in the structure of the cytoplasmic death domain from nine independent ALPS CD95 death-domain mutations result in a failure to bind the FADD/MORT1 signaling protein. Despite heterozygosity for the abnormal allele, lymphocytes from ALPS patients showed markedly decreased FADD association and a loss of caspase recruitment and activation after CD95 crosslinking. These data suggest that intracytoplasmic CD95 mutations in ALPS impair apoptosis chiefly by disrupting death-domain interactions with the signaling protein FADD/MORT1.     

A genetic disorder of lymphocyte apoptosis involving the fas pathway: The autoimmune lymphoproliferative syndrome

Autoimmune lymphoproliferative syndrome (ALPS) is a recently characterized human disorder that typically presents with lymphocyte accumulation in the first few years of life. This is often associated with the development of autoimmunity, most commonly affecting the hematopoietic system. A key laboratory feature is the marked expansion of double-negative (CD4- and CD8-) T cells that express the a/b T-cell receptor. ALPS is associated with defective Fas-mediated lymphocyte apoptosis, and in most patients, this results from a heterozygous mutation in the TNFRSF6 gene encoding Fas. The clinical features of ALPS reveal the importance of the Fas apoptotic pathway in maintaining lymphocyte homeostasis and protecting against autoimmunity and lymphoid malignancy.     

Immunophenotypic profiles in families with autoimmune lymphoproliferative syndrome

Autoimmune lymphoproliferative syndrome (ALPS) type Ia is caused by inherited defects in apoptosis and is characterized by nonmalignant lymphoaccumulation, autoimmunity, and increased alpha/beta(+) double-negative T cells (alpha/beta(+)-DNT cells). This study reports immunophenotypic findings in 166 members of 31 families with ALPS type Ia, associated with genetic mutations in the TNFRSF6 gene encoding Fas. The ALPS type Ia probands (n = 31) and relatives having both a Fas mutation and clinically proven ALPS (n = 28) showed significant expansion of CD8(+) T cells, alpha/beta(+)-DNT cells, gamma/delta(+)-DNT cells, CD3(+)/ HLA-DR(+) T cells, CD8(+)/CD57(+) T cells, and CD5(+) B cells. Relatives with Fas mutations, but without all the required criteria for ALPS (n = 42), had expansions of CD8(+) T cells, alpha/beta(+)-DNT cells, and gamma/delta(+)-DNT cells. Interestingly, relatives without a Fas mutation and with no features of ALPS (n = 65) demonstrated a small but significant expansion of CD8(+) T cells, both DNT cell subsets, and CD5(+) B cells. As compared to unrelated healthy controls, lymphocyte subset alterations were greatest in the probands, followed by the relatives with mutations and ALPS. Probands and relatives with mutations and ALPS also showed a lower number of CD4(+)/CD25(+) T cells that, in combination with an independent increase in HLA-DR(+) T cells, provided a profile predictive of the presence of clinical ALPS. Because quantitative defects in apoptosis were similar in mutation-positive relatives regardless of the presence of clinical ALPS, factors, other than modifiers of the Fas apoptosis pathway, leading to these distinctive immunophenotypic profiles most likely contribute to disease penetrance in ALPS.     

An inherited disorder of lymphocyte apoptosis: the autoimmune lymphoproliferative syndrome

The autoimmune lymphoproliferative syndrome (ALPS) affords novel insights into the mechanisms that regulate lymphocyte homeostasis and underlie the development of autoimmunity. This syndrome arises early in childhood in persons who inherit mutations in genes that mediate apoptosis, or programmed cell death. The timely deletion of lymphocytes is a way to prevent their accumulation and the persistence of cells that can react against the body's own antigens. In ALPS, defective lymphocyte apoptosis permits chronic, nonmalignant adenopathy and splenomegaly; the survival of normally uncommon "double-negative" CD3+ CD4- CD8- T cells; and the development of autoimmune disease. Most cases of ALPS involve heterozygous mutations in the lymphocyte surface protein Fas that impair a major apoptotic pathway. Detailed immunologic investigations of the cellular and cytokine profiles in ALPS show a prominent skewing toward a T-helper 2 phenotype; this provides a rational explanation for the humoral autoimmunity typical of patients with ALPS. Prospective evaluations of 26 patients and their families show an ever-expanding spectrum of ALPS and its major complications: hypersplenism, autoimmune hemolytic anemia, thrombocytopenia, and neutropenia. Defective apoptosis may also contribute to a heightened risk for lymphoma.     

A homozygous Fas ligand gene mutation in a patient causes a new type of autoimmune lymphoproliferative syndrome

Autoimmune lymphoproliferative syndrome (ALPS) is characterized by lymphoproliferation and autoimmune clinical manifestations and is generally caused by defective Fas-mediated apoptosis. This report describes the first homozygous FASL gene mutation in a woman with clinical and immunologic features of ALPS. T-cell blasts from the patient did not induce FasL-mediated apoptosis on Fas-transfected murine L1210 or on Jurkat cells, and activation-induced cell death was impaired. Furthermore, Fas-dependent cytotoxicity was drastically reduced in COS cells transfected with the mutant FasL. In addition, FasL expression on T-cell blasts from the patient was similar to that observed in a healthy control, despite its bearing the high-producer genotype -844C/C in the FASL promoter. Sequencing of the patient's FASL gene revealed a new mutation in exon 4 (A247E). The location of A247E in the FasL extracellular domain and the conservation of the protein sequence of that region recorded in 8 species different from humans support the essential role of FasL COOH terminal domain in Fas/FasL binding. These findings provide evidence that inherited nonlethal FASL abnormalities cause an uncommon apoptosis defect producing lymphoproliferative disease, and they highlight the need for a review of the current ALPS classification to include a new ALPS type Ic subgroup.     

Rituximab responsive immune thrombocytopenic purpura in an adult with underlying autoimmune lymphoproliferative syndrome due to a splice-site mutation (IVS7+2 T>C) affecting the Fas gene

A 36 yr-old man of Israeli descent with a history of childhood splenectomy for severe thrombocytopenia and a family history of autoimmune lymphoproliferative syndrome (ALPS), presented with severe immune thrombocytopenic purpura refractory to standard therapy. He was found to possess a heterozygous mutation in the Fas gene (also termed TNFRSF6, CD95, Apo-1) affecting the donor splice site of intron 7 (IVS7+2 T>C). This frameshift mutation truncates the cytoplasmic domain of the Fas death receptor, resulting in circulating CD4/8 double negative T lymphocytes, lymphadenopathy and autoimmune complications typical of ALPS. Administration of Rituximab in this patient was associated with a durable hematologic response (currently more than 12 months). This report highlights the need to consider rare inherited causes of thrombocytopenia in adults with a family history of immune cytopenia(s) and the effective use of anti-CD20 monoclonal antibody in patients unresponsive to immunosuppression and splenectomy.     

Lymphoproliferative syndrome with autoimmunity: A possible genetic basis for dominant expression of the clinical manifestations.

Fas (CD95/Apo-1) mutations were previously reported as the genetic defect responsible for human lymphoproliferative syndrome associated with autoimmune manifestations (also known as autoimmune lymphoproliferative syndrome or Canale-Smith syndrome). We have identified 14 new heterozygous Fas mutations. Analysis of patients and families allow us to further dissect this syndrome with regards to the relationship between Fas mutations, inheritance pattern, and phenotype as observed on long-term follow-up. In vitro studies show that lymphocytes from all Fas mutant carriers exhibit a Fas-antibody-induced apoptosis defect. However, among the 8 inherited mutations, 4 of 4 Fas missense mutations were associated with high clinical penetrance, whereas 3 of 4 mutations leading to a truncated Fas product were associated with variable clinical penetrance. This suggests that a second defect, in another yet undefined factor involved in apoptosis and/or lymphoproliferation control, is necessary to induce full clinical expression of the disease. These results also indicate that the currently available antibody-mediated in vitro apoptosis assay does not necessarily reflect the in vivo ability of abnormal Fas molecules to trigger lymphocyte death. In addition, we found that lymphoproliferative manifestations resolved with age, whereas immunological disorders [ie, hypergammaglobulinemia and detection of TcR alphabeta(+) CD4(-) CD8(-) lymphocytes] persisted. This observation suggests that Fas-mediated apoptosis plays a more important role in lymphocyte homeostasis in early childhood than later on in life.     

NRAS mutation causes a human autoimmune lymphoproliferative syndrome

The p21 RAS subfamily of small GTPases, including KRAS, HRAS, and NRAS, regulates cell proliferation, cytoskeletal organization, and other signaling networks, and is the most frequent target of activating mutations in cancer. Activating germline mutations of KRAS and HRAS cause severe developmental abnormalities leading to Noonan, cardio-facial-cutaneous, and Costello syndrome, but activating germline mutations of NRAS have not been reported. Autoimmune lymphoproliferative syndrome (ALPS) is the most common genetic disease of lymphocyte apoptosis and causes autoimmunity as well as excessive lymphocyte accumulation, particularly of CD4(-), CD8(-) alphabeta T cells. Mutations in ALPS typically affect CD95 (Fas/APO-1)-mediated apoptosis, one of the extrinsic death pathways involving TNF receptor superfamily proteins, but certain ALPS individuals have no such mutations. We show here that the salient features of ALPS as well as a predisposition to hematological malignancies can be caused by a heterozygous germline Gly13Asp activating mutation of the NRAS oncogene that does not impair CD95-mediated apoptosis. The increase in active, GTP-bound NRAS augments RAF/MEK/ERK signaling, which markedly decreases the proapoptotic protein BIM and attenuates intrinsic, nonreceptor-mediated mitochondrial apoptosis. Thus, germline activating mutations in NRAS differ from other p21 Ras oncoproteins by causing selective immune abnormalities without general developmental defects. Our observations on the effects of NRAS activation indicate that RAS-inactivating drugs, such as farnesyltransferase inhibitors should be examined in human autoimmune and lymphocyte homeostasis disorders.     

High levels of osteopontin associated with polymorphisms in its gene are a risk factor for development of autoimmunity/lymphoproliferation

The autoimmune/lymphoproliferative syndrome (ALPS) displays defective function of Fas, autoimmunities, lymphadenopathy/splenomegaly, and expansion of CD4/CD8 double-negative (DN) T cells. Dianzani autoimmune/lymphoproliferative disease (DALD) is an ALPS variant lacking DN cells. Both forms have been ascribed to inherited mutations hitting the Fas system but other factors may be involved. A pilot cDNA array analysis on a DALD patient detected overexpression of the cytokine osteopontin (OPN). This observation was confirmed by enzyme-linked immunosorbent assay (ELISA) detection of higher OPN serum levels in DALD patients (n = 25) than in controls (n = 50). Analysis of the OPN cDNA identified 4 polymorphisms forming 3 haplotypes (A, B, and C). Their overall distribution and genotypic combinations were different in patients (N = 26) and controls (N = 158) (P <.01). Subjects carrying haplotype B and/or C had an 8-fold higher risk of developing DALD than haplotype A homozygotes. Several data suggest that these haplotypes influence OPN levels: (1) in DALD families, high levels cosegregated with haplotype B or C; (2) in healthy controls, haplotype B or C carriers displayed higher levels than haplotype A homozygotes; and (3) in AB and AC heterozygotes, mRNA for haplotype B or C was more abundant than that for haplotype A. In vitro, exogenous OPN decreased activation-induced T-cell death, which suggests that high OPN levels are involved in the apoptosis defect.     

Eosinophilia is associated with a higher mortality rate among patients with autoimmune lymphoproliferative syndrome

Autoimmune lymphoproliferative syndrome (ALPS) is a disorder associated with heritable defects in lymphocyte apoptosis that result in chronic nonmalignant lymphadenopathy, splenomegaly, and autoimmunity. To examine the prevalence, mechanisms, and potential implications of eosinophilia in ALPS, we reviewed data retrospectively from 187 consecutive ALPS patients and their family members studied at the National Institutes of Health. ALPS patients with eosinophilia were compared with ALPS patients without eosinophilia with respect to their clinical and immunologic phenotype. Potential mechanisms for the eosinophilia, including abnormal Fas-mediated eosinophil apoptosis, increased production of eosinophilopoietic cytokines, and presence of anti-eosinophilic autoantibodies were also explored in a small number of patients from whom samples were available. Analysis of data from 68 ALPS patients and 119 of their relatives identified a distinct subgroup of patients with prominent and persisting eosinophilia that proved to be associated with increased numbers of peripheral blood leukocytes (PBL) of multiple lineages and a trend towards increased serum IgE levels. Eosinophilic ALPS patients also had a significantly higher risk of death due to infectious complications. Although the specific etiology of the eosinophilia in these patients remains uncertain, it does not appear to be associated with an altered serum cytokine profile, increased survival responsiveness of eosinophils to IL-5, defective Fas-mediated eosinophil apoptosis, or anti-eosinophil antibodies. Eosinophilia defines a distinct subgroup of ALPS patients with increased serum IgE levels, increased numbers of PBL of multiple lineages, and higher mortality from infectious complications.     

Dysregulation of CD95/CD95 Ligand-Apoptotic Pathway in CD3+ Large Granular Lymphocyte Leukemia

CD95 (Fas)-induced apoptosis plays a critical role in theelimination of activated lymphocytes and induction of peripheral tolerance. Defects in CD95/CD95L (Fas-Ligand)-apoptotic pathway have been recognized in autoimmune lymphoproliferative diseases (ALPS)and lpr or gld mice and attributed to CD95 and CD95Lgene mutations, respectively. Large granular lymphocyte (LGL) leukemia is a chronic disease characterized by a proliferation ofantigen-activated cytotoxic T lymphocytes. Autoimmune features such ashypergammaglobulinemia, rheumatoid factor, and circulating immunecomplexes are common features in LGL leukemia and ALPS. Therefore, wehypothesize that expansion of leukemic LGL may be secondary to adefective CD95 apoptotic pathway. In this study, we investigatedexpression of CD95 and CD95L in 11 patients with CD3⁺ LGLleukemia and explored the apoptotic response to agonistic CD95monoclonal antibody (MoAb). We found that leukemic LGL from eachpatient expressed constitutively high levels of CD95/CD95L, similar tothose seen in normal activated T cells. However, cells from 9 of these11 patients were totally resistant to anti-CD95-induced apoptosis.Similarly, cells were resistant to anti-CD3-MoAb-triggered cell death.Lack of anti-CD95-induced apoptosis was not due to mutations in theCD95 antigen. Leukemic LGL were not intrinsically resistant toCD95-dependent death, because LGL from all but 1 patient underwentapoptosis after phytohemagglutinin/interleukin-2 activation. Thepatient whose leukemic LGL were intrinsically resistant to CD95 had anaggressive form of LGL leukemia that was resistant to combinationchemotherapy. These findings that leukemic LGL are resistant toCD95-dependent apoptosis despite expressing high levels of CD95 aresimilar to observations made in CD95L transgenic mice. These datasuggest that LGL leukemia may be a useful model of dysregulatedapoptosis causing human malignancy and autoimmune disease.     

Autoimmune lymphoproliferative syndrome: report of two cases and review of the literature

Autoimmune lymphoproliferative syndrome (ALPS) is a rare disease occurring in childhood. Recently, it has been shown that heritable mutations in Fas or Fas ligand genes, which regulate lymphocyte survival by triggering apoptosis of lymphocytes, are the most frequent cause of ALPS. Patients with ALPS frequently have lymphadenopathy, splenomegaly and hepatomegaly, especially at young ages. A positive result of the Direct Coomb's test, autoimmune hemolytic anemia, and idiopathic thrombocytopenic purpura are the most common features of autoimmunity in patients with ALPS. Elevated numbers and percentages (>1%) of double-negative (CD4-CD8-) T cells, and characteristic pathologic findings in lymph nodes or spleen are other important diagnostic features. In this report, we present the clinical, immunologic, and pathologic features of two children who were diagnosed with ALPS. The early recognition of ALPS in children with enlarged lymph nodes, hepatosplenomegaly, and autoimmune hematologic features has important diagnostic and prognostic value in avoiding expensive and time-consuming studies and unnecessary treatments. The ratio of CD4-CD8- T cells, immunoglobulin levels and the histopathologic features of lymph nodes should be rapidly determined in these patients in order to establish an early diagnosis and treatment.     

Dyserythropoiesis associated with a fas-deficient condition in childhood

Defective lymphocyte apoptosis caused by mutations of the Fas gene can result in an autoimmune lymphoproliferative syndrome (ALPS) in humans. We report two cases of dyserythropoiesis associated with a Fas-deficient condition in childhood. In both cases, dyserythropoiesis predominated on the more mature erythroblasts, and was associated with a lymphoproliferative syndrome as well as with haemolytic anaemia, hypergammaglobulinaemia and the expansion of an unusual population of CD4- CD8- T cells that express the alpha/beta T-cell receptor. The regression of dyserythropoiesis under steroid therapy suggested that it resulted from an autoimmune mechanism, itself secondary to the lymphocyte Fas apoptosis deficiency. Fas-defective apoptosis may be a new aetiology for childhood dyserythropoiesis.     

Causes and consequences of the autoimmune lymphoproliferative syndrome

Autoimmune lymphoproliferative syndrome (ALPS) is the first autoimmune hematological disease whose genetic basis has been defined. It is a disorder of apoptosis in which the inability of lymphocytes to die leads to lymphadenopathy, hypersplenism, and autoimmune cytopenias of childhood onset. More than 200 ALPS patients have been studied over the last 15 years and followed by our colleagues and ourselves at the Clinical Center of the National Institutes of Health. Based upon this experience we have determined that patients with germline mutations of the intracellular domain of Fas protein, the most frequent single genetic cause of ALPS, have a significantly increased risk of developing Hodgkin and non-Hodgkin lymphoma (NHL), underscoring the critical role played by cell surface receptor-mediated apoptosis in eliminating redundant proliferating lymphocytes with autoreactive and oncogenic potential. The major determinants of morbidity and mortality in ALPS are the severity of the autoimmune disease, hypersplenism, asplenia-related sepsis, and the risk of lymphoma, which in itself requires long-term surveillance. Though most episodes of cytopenias respond to courses of conventional immunomodulatory agents, some ALPS patients, especially those with massive splenomegaly and hypersplenism, may require splenectomy and/or ongoing immunosuppressive treatment. Thus, ALPS highlights the importance of cell death pathways in health and disease.     

Causes and consequences of the autoimmune lymphoproliferative syndrome

Autoimmune lymphoproliferative syndrome (ALPS) is the first autoimmune hematological disease whose genetic basis has been defined. It is a disorder of apoptosis in which the inability of lymphocytes to die leads to lymphadenopathy, hypersplenism, and autoimmune cytopenias of childhood onset. More than 200 ALPS patients have been studied over the last 15 years and followed by our colleagues and ourselves at the Clinical Center of the National Institutes of Health. Based upon this experience we have determined that patients with germline mutations of the intracellular domain of Fas protein, the most frequent single genetic cause of ALPS, have a significantly increased risk of developing Hodgkin and non-Hodgkin lymphoma (NHL), underscoring the critical role played by cell surface receptor-mediated apoptosis in eliminating redundant proliferating lymphocytes with autoreactive and oncogenic potential. The major determinants of morbidity and mortality in ALPS are the severity of the autoimmune disease, hypersplenism, asplenia-related sepsis, and the risk of lymphoma, which in itself requires long-term surveillance. Though most episodes of cytopenias respond to courses of conventional immunomodulatory agents, some ALPS patients, especially those with massive splenomegaly and hypersplenism, may require splenectomy and/or ongoing immunosuppressive treatment. Thus, ALPS highlights the importance of cell death pathways in health and disease.