Autoimmune lymphoproliferative syndrome: etiology, diagnosis, and management

Updated Understanding of Autoimmune Lymphoproliferative Syndrome (ALPS)

Autoimmune lymphoproliferative syndrome (ALPS), a disorder characterized by immune dysregulation due to disrupted lymphocyte homeostasis, is mainly resulted from the mutations in FAS-mediated apoptotic pathway. In addition, other mutations of the genes such as Fas-ligand (FASLG), Caspase 10 (CASP10) and Caspase 8 (CASP8), NRAS and KRAS have also been observed in a small number of patients with ALPS or ALPS-related disorders. However, approximately 20-30% of patients with ALPS have unidentified defect. Its clinical manifestations observed in multiple family members include unexplained lymphadenopathy, hepatosplenomegaly, autoimmune cytopenias such as thrombocytopenia, neutropenia, and anemia due to excessive production of antibodies by lymphocytes, elevated number of double-negative T (DNT) cells, and increased risk of lymphoma. As a very rare disease, ALPS was first characterized in the early 1990s. More than 300 families with hereditary ALPS have been reported till now; nearly 500 patients from these families have been studied and followed worldwide over the last 20 years. ALPS has historically considered as a primary immune defect presenting in early childhood, however, recent studies have shown that it may be more common than previous thought because adult onset presentation is increasingly becoming recognized and more adult ALPS patients are diagnosed. The new genetic and biological insights have improved the understanding of ALPS and a number of targeted therapeutic strategies such as mycophenolate mofetil, sirolimus, and pentostatin have been successfully applied in ALPS patients with promising treatment efficacy. This article comprehensively reviews the clinical and laboratory manifestations, new research advances in the molecular pathogenesis, diagnosis and treatments of this disorder.

New advances in the diagnosis and treatment of autoimmune lymphoproliferative syndrome

PURPOSE OF REVIEW

Autoimmune lymphoproliferative syndrome (ALPS) is a disorder of disrupted lymphocyte homeostasis, resulting from mutations in the Fas apoptotic pathway. Clinical manifestations include lymphadenopathy, splenomegaly, and autoimmune cytopenias. A number of new insights have improved the understanding of the genetics and biology of ALPS. These will be discussed in this review.

RECENT FINDINGS

A number of key observations have been made recently that better define the pathophysiology of ALPS, including the characterization of somatic FAS variant ALPS, the identification of haploinsufficiency as a mechanism of decreased Fas expression, and the description of multiple genetic hits in FAS in some families that may explain the variable penetrance of the disease. In addition, ALPS has been shown to be a more common condition, as patients diagnosed with other disorders, including Evans syndrome and common variable immune deficiency, have been found to have ALPS. Finally, the treatment of the disease has changed as splenectomy and rituximab have been shown to have unexpected ALPS-specific toxicities, and mycophenolate mofetil and sirolimus have been demonstrated to have marked activity against the disease.

SUMMARY

On the basis of novel advances, the diagnostic algorithm and recommended treatment for ALPS have changed significantly, improving quality of life for many patients.

Identifying autoimmune lymphoproliferative syndrome in children with Evans syndrome: a multi-institutional study

Autoimmune lymphoproliferative syndrome (ALPS) is a disorder of abnormal lymphocyte survival caused by dysregulation of the Fas apoptotic pathway. Clinical manifestations of ALPS include autoimmune cytopenias, organomegaly, and lymphadenopathy. These findings overlap with Evans syndrome (ES), defined by presence of at least 2 autoimmune cytopenias. We hypothesized a subset of patients with ES have ALPS and tested 45 children at 22 institutions, measuring peripheral blood double-negative T cells (DNTs) and Fas-mediated apoptosis. ALPS was diagnosed in 47% of patients tested. Markedly elevated DNTs (> or = 5%) were a strong predictor of ALPS (positive predictive value = 94%), whereas no patients with DNTs less than 2.5% had ALPS on apoptosis testing. Severity of cytopenias and elevated immunoglobulin levels also predicted ALPS. This is the largest published series describing children with ES and documents a high rate of ALPS among pediatric ES patients. These data suggest that children with ES should be screened for ALPS with DNTs.

Splenectomy in two children with autoimmune lymphoproliferative syndrome and massive splenomegaly

Treatment of patients with ALPS has varied but presently there is no consensus about the optimal therapy. Splenectomy is an option but data regarding the postsplenectomy outcome in pediatric ALPS patients remain very limited. We present two children who suffered from anemia and physical discomfort from the large spleen. Both patients underwent uneventful splenectomy and experienced significant improvement in cytopenia, daily activity and well-being. Furthermore the youngest patient showed a significant catch-up growth. We conclude that in selected patients with marked splenomegaly and ALPS, splenectomy may be considered a treatment option.

Advances in the management and understanding of autoimmune lymphoproliferative syndrome (ALPS)

Autoimmune lymphoproliferative syndrome (ALPS) is a disorder of T cell dysregulation caused by defective Fas-mediated apoptosis. Patients with ALPS can develop a myriad of clinical manifestations including lymphadenopathy, hepatosplenomegaly, autoimmunity and increased rates of malignancy. ALPS may be more common that originally thought, and testing for ALPS should be considered in patients with unexplained lymphadenopathy, hepatosplenomegaly, and/or autoimmunity. As the pathophysiology of ALPS is better characterized, a number of targeted therapies are in preclinical development and clinical trials with promising early results. This review describes the clinical and laboratory manifestations found in ALPS patients, as well as the molecular basis for the disease and new advances in treatment.