Autoimmune lymphoproliferative syndrome

A rare genetic disorder affecting the immune system

Autoimmune lymphoproliferative syndrome
Synonyms	Canale-Smith syndrome
Specialty	Immunology, Hematology, Pediatrics
Symptoms	Lymphadenopathy, splenomegaly, autoimmune cytopenias, recurrent fevers, fatigue
Complications	Hemolytic anemia, thrombocytopenia, neutropenia, increased risk of lymphoma
Usual onset	Usually in early childhood
Duration	Chronic
Types	ALPS-FAS, ALPS-FASL, ALPS-CASP10, and others based on genetic mutation
Causes	Mutations in the FAS gene or related genes involved in lymphocyte apoptosis
Risk factors	Family history of ALPS or related immune disorders
Diagnosis	Clinical symptoms, elevated double-negative T cells, genetic testing, biomarkers such as IL-10, vitamin B12, and sFASL
Differential diagnosis	Common variable immunodeficiency, systemic lupus erythematosus, Evans syndrome, infectious mononucleosis
Prevention	None known
Treatment	Immunosuppressive therapy, corticosteroids, intravenous immunoglobulin (IVIG), splenectomy in severe cases
Medication	Sirolimus, mycophenolate mofetil, rituximab, corticosteroids
Prognosis	Variable; many respond well to treatment, but lifelong monitoring is often needed
Frequency	Rare
Deaths	Can occur from complications or progression to lymphoma

Autoimmune lymphoproliferative syndrome (ALPS) is a rare genetic disorder characterized by the abnormal regulation of the immune system, leading to the proliferation of lymphocytes and the development of autoimmunity. This condition is primarily caused by mutations in genes that are crucial for the process of apoptosis, which is the programmed cell death necessary for maintaining immune system balance.

Pathophysiology

ALPS is primarily associated with mutations in the FAS gene, which encodes a protein that plays a critical role in the apoptotic pathway. The FAS protein is a cell surface receptor that, when bound to its ligand, initiates a cascade of events leading to cell death. Mutations in the FAS gene disrupt this process, resulting in the accumulation of lymphocytes, particularly T cells, and the development of lymphoproliferative disorders.

The failure of apoptosis in ALPS leads to the accumulation of autoreactive lymphocytes, which can attack the body's own tissues, causing autoimmune diseases. Common autoimmune manifestations in ALPS include autoimmune hemolytic anemia, immune thrombocytopenic purpura, and neutropenia.

Clinical Features

Patients with ALPS typically present with chronic lymphadenopathy and splenomegaly. The condition often manifests in early childhood, although the age of onset can vary. In addition to lymphoproliferation, individuals with ALPS may experience recurrent infections due to immune dysregulation and the presence of autoantibodies.

Other clinical features may include:

• Hepatomegaly
• Skin rashes
• Arthritis
• Uveitis

Diagnosis

The diagnosis of ALPS is based on clinical criteria, laboratory findings, and genetic testing. Key laboratory findings include elevated levels of double-negative T cells (TCRαβ+ CD4− CD8−) and increased serum levels of vitamin B12 and interleukin-10. Genetic testing can confirm mutations in the FAS gene or other related genes involved in the apoptotic pathway.

Management

Management of ALPS involves addressing both the lymphoproliferative and autoimmune components of the disease. Treatment options may include:

• Corticosteroids to manage autoimmune cytopenias
• Immunosuppressive drugs such as mycophenolate mofetil or sirolimus
• Intravenous immunoglobulin (IVIG) for severe autoimmune manifestations
• Splenectomy in cases of severe splenomegaly or refractory cytopenias

Prognosis

The prognosis for individuals with ALPS varies depending on the severity of the disease and the response to treatment. With appropriate management, many patients can lead relatively normal lives, although they may require ongoing monitoring and treatment for autoimmune complications.

Related pages

• Autoimmune disease
• Lymphoproliferative disorder
• Apoptosis
• Genetic disorder