Autoimmune lymphoproliferative syndrome overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] David Teachey, MD [2]
Overview
Autoimmune lymphoproliferative syndrome is a form of lymphoproliferative disorder. It affects lymphocyte apoptosis. Autoimmune lymphoproliferative syndrome (ALPS) is a rare disorder of abnormal lymphocyte survival caused defective Fas mediated apoptosis. ALPS was first reported in 1967 by Canale and Smith; thus it was named initially as Canale and Smith syndrome. According to the 2010 revised guidelines, now ALPS is defined by the presence of chronic, non-malignant, and non-infectious lymphadenopathy along with autoimmune cytopenias. ALPS was first explained in 1990 in a cohort of patients with chronic lymphoproliferation and increased numbers of double-negative T cells (DNTs). Also ALPS is associated with increased level of IL-10,IL-12,vitamin B 12, soluble FAS ligand and IgG in serum. In vitro evidence of defective FAS mediated apoptosis is also found in ALPS. For proper development of immune system and regulation of apoptosis FAS receptor pathway is very important. Heterozygous mutation in genes in the FAS pathway cause ALPS. Other different kinds of mutations also identified and gene based nomenclature is recommended nowadays to describe new cases. The true incidence and prevalence of ALPS are still not known due to the high rate of misdiagnosis or remain undiagnosed. FAS plays an important role in controlling the malignant transformation of lymphocytes. Hence, ALPS patients are at high risk of developing lymphoma. Germline FAS mutation is the most common while somatic mutation is the second most common cause. Many of the patients with ALPS have unidentified genetic defects. ALPS mostly occur in early childhood with a median age of 18 months. Common clinical features are chronic lymphadenopathy(95% of patients), splenomegaly(90% of patients), or hepatomegaly(40-50% of patients). Lymphoproliferation is the earliest symptom with a median age of onset is 11.5 months. Lymphoproliferation can get worsen in adolescence and eventually get resolved in early 20s.Most of the ALPS patients have non tender, enlarged lymph nodes for a prolonged duration. In ALPS, second most common clinical manifestations are related to autoimmunity as hemolytic anemia, thrombocytopenia and neutropenia. Cytopenias are accompanied with elevated or reduced serum IgG.