Autoimmune Lymphoproliferative Syndrome Workup
- Author: Luke M Webb, MD; Chief Editor: Harumi Jyonouchi, MD more...
In evaluating a child with chronic lymphadenopathy or splenomegaly with or without cytopenias, one must evaluate for and rule out numerous diagnoses, including malignancies and chronic infection. A history of constitutional symptoms (eg, weight loss, anorexia, pallor, early fatigue, easy bruising, or frequent ear and throat infection) in conjunction with the physical findings previously mentioned (see Presentation) warrants an evaluation to exclude these conditions.
Depending on the patient’s history and risk factors, initial evaluation may include a complete blood count (CBC) count with differential, as well as immunoglobulin, serum lactate dehydrogenase (LDH), and uric acid levels.
Pediatric patients who have acute lymphadenopathy with concerning or atypical features (including fixed or hard nodes or massive lymphadenopathy) or chronic lymphadenopathy without an identified cause should be referred to a pediatric hematologist for consideration of lymph node biopsy and further evaluation.
Lymph node biopsy findings are unique in autoimmune lymphoproliferative syndrome (ALPS), and hematologists, surgeons, and pathologists involved in performing and interpreting biopsy results should be familiar with these findings and include the diagnosis of ALPS if these findings are present on biopsy.
To meet the criteria for a definitive diagnosis of ALPS, both of the 2 required criteria and at least 1 of the primary accessory criteria must be present (see the image below). If both of the required criteria and at least 1 of the secondary accessory criteria are present, the diagnosis of ALPS is probable rather than definitive.
The 2 required diagnostic criteria for ALPS are as follows:
Chronic, nonmalignant, noninfectious lymphadenopathy or splenomegaly lasting at least 6 months
Elevated T-cell receptor (TCR) α/β CD3 + CD4 –/CD8 – T cells, or double-negative T (DNT) cells (≥1.5% of total lymphocytes or 2.5% of CD3 + lymphocytes), in the setting of normal or elevated lymphocyte counts
The primary accessory criteria are as follows:
Defective lymphocyte apoptosis in 2 separate assays 
A somatic or germline pathogenic mutation in FAS, FASLG, or CASP10
The secondary accessory criteria are as follows :
An elevated plasma level (>200 pg/mL) of soluble Fas ligand (FasL), elevated plasma interleukin (IL)–10 levels (>20 pg/mL), elevated plasma IL-18 levels (>500 pg/mL), or elevated serum or plasma vitamin B 12 levels (>1500 ng/L)
Typical immunohistochemical findings reviewed by an experienced hematopathologist
Autoimmune cytopenia (hemolytic anemia, neutropenia, or thrombocytopenia) plus elevated immunoglobulin G (IgG) levels (polyclonal)
Family history of a nonmalignant, noninfectious lymphoproliferation, with or without autoimmunity
Although no single laboratory study is diagnostic of ALPS, there are several laboratory tests that should be obtained.
Autoantibodies are frequently found in patients with ALPS. A study of 79 ALPS patients detected autoantibodies in 81%. The most common autoantibodies detected in patients with ALPS are antierythrocyte antibodies, which may be detected by means of a Coombs direct antiglobulin test (DAT). Other common circulating autoantibodies include antiplatelet and antineutrophil antibodies.
A CBC with differential may reveal lymphocytosis, reticulocytosis, thrombocytopenia, anemia, neutropenia, monocytosis, or eosinophilia. Hypergammaglobulinemia is also a common feature in ALPS, and a quantitative immunoglobulin panel should be obtained if a diagnosis of ALPS is suspected or confirmed.
The lymphocyte dysregulation seen in patients with ALPS results in an increase in TCR α/β DNT cells in the peripheral circulation, bone marrow, spleen, or lymphoid tissues. These lymphocytes may be detected by flow cytometric immunophenotyping of samples from any of these sites. Patients with ALPS characteristically demonstrate an elevated proportion of these cells.
Most patients with ALPS also exhibit defective lymphocyte apoptosis. Lymphocyte apoptosis must be assayed in vitro, and only specialized laboratories are currently performing this analysis.
One method used for assessing lymphocyte apoptosis is to culture the patient’s peripheral lymphocytes with IL-2 for several days, then stimulating them with phytohemagglutinin and attempting to induce apoptosis by adding a monoclonal antibody that specifically binds to the activated Fas molecule on the cell’s surface. Most cells in normal individuals undergo apoptosis under these conditions. However, the lymphocytes from patients with ALPS have defective apoptosis (ie, < 50%).
Other abnormal laboratory findings that are commonly found in ALPS patients include elevated soluble FasL levels, elevated transaminases (in the subset of patients with autoimmune hepatitis), elevated plasma IL-10 or IL-18 levels, proteinuria (in patients with glomerulonephritis), and elevated serum levels of vitamin B-12.
Molecular genetic testing should also be obtained in patients with clinical or laboratory features consistent with a diagnosis of ALPS. Specifically, genetic analysis of the Fas receptor gene (TNFRSF6), the FasL gene (TNFSF6), the caspase 10 gene (CASP-10), and the caspase 8 gene (CASP-8) is warranted.
Mutations of the FAS gene have been identified as the cause of most (74%) cases of ALPS. Therefore, the authors recommend initially testing for mutations of FAS, followed by analysis of the other genes only when analysis of FAS fails to reveal a causative mutation.
This testing is important for the following 2 reasons:
If a mutation is identified, genetic counseling must be provided to the family, and other family members must be invited for screening evaluations
The location of the specific gene mutation is important for the prognosis because certain mutation loci are associated with a higher risk of complications, including lymphoma; patients with a mutation of the intracellular domain of FAS have a 14-fold higher risk of non-Hodgkin lymphoma and a 51-fold higher risk of Hodgkin lymphoma 
Computed Tomography and Positron Emission Tomography
Although imaging studies are not used in establishing a diagnosis of ALPS, once the diagnosis has been made, it is important to obtain baseline and periodic computed tomography (CT) scans. CT of the neck, chest, abdomen and pelvis at the time of diagnosis help establish the extent and location of the patient’s lymphadenopathy.
Because of the increased risk of lymphoma in patients with ALPS, frequent surveillance with serial CT scans is an important part of the long-term management of these patients. As a consequence of the chronic fluctuating nature of their lymphadenopathy, ALPS patients may undergo repeated lymph node biopsies to help rule out lymphoma if they develop systemic symptoms in addition to focal changes of adenopathy.
Positron emission tomography (PET) using18 fluoro-2-deoxy-D-glucose (FDG), or FDG-PET, is now the standard for staging and follow-up evaluations of cancers, including lymphomas. Prospective studies are under way to determine if whole-body FDG-PET can be used to help differentiate chronic benign lymphadenopathy in patients with ALPS from ALPS-associated lymphomas.[7, 16] If this proves to be a useful tool, it may decrease the number of lymph node biopsies these patients are required to undergo (see the image below).
Lymph Node Biopsy
Lymph node biopsies are typically performed in ALPS patients. Such biopsies reveal findings unique to ALPS (see Histologic Findings). If the biopsy findings obtained in a patient with lymphadenopathy are consistent with a diagnosis of ALPS, further laboratory testing, including flow cytometric immunophenotyping and genetic testing, is warranted.
[#WorkupHistologicFindings]At the time of diagnosis, biopsy is used to look for histology suggestive of ALPS, as well as to rule out lymphoma. ALPS is associated with both chronic lymphadenopathy and a significant increase in the risk for lymphoma. In view of these 2 associations, lymph node biopsy may be required if a sudden or dramatic change in a node is noted, particularly if these changes are associated with concerning constitutional symptoms, such as weight loss, fever, and night sweats.
Serial CT and PET may be used as tools to mitigate the tendency to perform repeated lymph node biopsies while still effectively monitoring these patients for malignancy.
The elevated percentage of TCR α/β DNT cells caused by the lymphocyte dysregulation seen in ALPS results in fairly characteristic histopathologic findings on lymph node biopsy. These findings include follicular hyperplasia and paracortical expansion with a mixed infiltrate containing the DNT cells. This specific histologic pattern can help distinguish ALPS from other benign and malignant lymphoproliferative lesions.
Evaluation of lymph node tissue for clonality by means of immunoglobulin and TCR gene rearrangements and cytogenetic analysis for chromosomal aneuploidy are also important for helping to rule out the diagnosis of lymphoma in ALPS patients who have chronic lymphadenopathy.
A specific staging system that can be used to establish a prognosis in patients with ALPS has not been established. However, the degree of generalized lymphadenopathy can be documented longitudinally in a consistent fashion by using the following guidelines:
Grade 1 - Few shotty nodes
Grade 2 - Multiple 1-2 cm nodes
Grade 3 - Multiple nodes, some larger than 2 cm
Grade 4 - Extensive visible adenopathy
This grading is best performed by using physical examination and CT scanning in the clinical setting.
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