Viral infection is a very common cause of lymphoproliferative disorders. In children, the most common is believed to be congenital HIV infection because it is highly associated with acquired immunodeficiency, which often leads to lymphoproliferative disorders.

Boys with X-linked immunodeficiency syndrome are at a higher risk of mortality associated with Epstein-Barr Virus infections, and are predisposed to develop a lymphoproliferative disorder or lymphoma.

Children with common variable immune deficiency (CVID) are also at a higher risk of developing a lymphoproliferative disorder.

Some disorders that predispose a person to lymphoproliferative disorders are severe combined immuno deficiency (SCID), Chédiak-Higashi syndrome, Wiskott-Aldrich syndrome (an X-linked recessive disorder), and ataxia telangiectasia.

Even though ataxia telangiectasia is an autosomal recessive disorder, people who are heterozygotes for this still have an increased risk of developing a lymphoproliferative disorder.

The disease is an uncontrolled proliferation of B cell lymphocytes latently infected with Epstein-Barr virus. Production of an interleukin-10, an endogenous, pro-regulatory cytokine, has also been implicated.

In immunocompetent patients, Epstein-Barr virus can cause infectious mononucleosis in adolescents, which is otherwise asymptomatic in children during their childhood. However, in immunosuppressed transplant patients, the lack of T-cell immunosurveillance can lead to the proliferation of these EBV-infected of B-lymphocytes.

However, calcineurin inhibitors (tacrolimus and ciclosporin), used as immunosuppressants in organ transplantation inhibit T cell function, and can prevent the control of the B cell proliferation.

Depletion of T cells by use of anti-T cell antibodies in the prevention or treatment of transplant rejection further increases the risk of developing post-transplant lymphoproliferative disorder. Such antibodies include ATG, ALG and OKT3.

Polyclonal PTLD may form tumor masses and present with symptoms due to a mass effect, e.g. symptoms of bowel obstruction. Monoclonal forms of PTLD tend to form a disseminated malignant lymphoma.

The 5 year survival has been noted as 89% in at least one study from France of 201 patients with T-LGL leukemia.

Secondary immunodeficiencies, also known as acquired immunodeficiencies, can result from various immunosuppressive agents, for example, malnutrition, aging, particular medications (e.g., chemotherapy, disease-modifying antirheumatic drugs, immunosuppressive drugs after organ transplants, glucocorticoids) and environmental toxins like mercury and other heavy metals, pesticides and petrochemicals like styrene, dichlorobenzene, xylene, and ethylphenol. For medications, the term "immunosuppression" generally refers to both beneficial and potential adverse effects of decreasing the function of the immune system, while the term "immunodeficiency" generally refers solely to the adverse effect of increased risk for infection.

Many specific diseases directly or indirectly cause immunosuppression. This includes many types of cancer, particularly those of the bone marrow and blood cells (leukemia, lymphoma, multiple myeloma), and certain chronic infections. Immunodeficiency is also the hallmark of acquired immunodeficiency syndrome (AIDS), caused by the human immunodeficiency virus (HIV). HIV directly infects a small number of T helper cells, and also impairs other immune system responses indirectly.

Various hormonal and metabolic disorders can also result in immune deficiency including anemia, hypothyroidism, diabetes and hypoglycemia.

Smoking, alcoholism and drug abuse also depress immune response.

Primary cerebral lymphoma (or "primary central nervous system lymphoma") is a form of NHL. It is very rare in immunocompetent people, with an incidence of 5–30 cases per million person-years. However the incidence in immunocompromised individuals is greatly increased, up to 100 per million person-years.

Primary cerebral lymphoma is strongly associated with Epstein–Barr virus (EBV). The presence of EBV DNA in cerebrospinal fluid is highly suggestive of primary cerebral lymphoma.

Treatment of AIDS patients with antiretroviral drugs reduces the incidence of primary cerebral lymphoma.

Of all cancers involving the same class of blood cell, 2.3% of cases are Burkitt lymphoma. Epstein-Barr virus infection is strongly correlated with this cancer.

T-LGLL is a rare form of leukemia, comprising 2-3% of all cases of chronic lymphoproliferative disorders.

Post-transplant lymphoproliferative disorder (PTLD) is the name given to a B-cell proliferation due to therapeutic immunosuppression after organ transplantation. These patients may develop infectious mononucleosis-like lesions or polyclonal polymorphic B-cell hyperplasia. Some of these B-cells may undergo mutations which will render them malignant, giving rise to a lymphoma.

In some patients, the malignant cell clone can become the dominant proliferating cell type, leading to frank lymphoma, a group of B cell lymphomas occurring in immunosuppressed patients following organ transplant.

A number of rare diseases feature a heightened susceptibility to infections from childhood onward. Primary Immunodeficiency is also known as congenital immunodeficiencies. Many of these disorders are hereditary and are autosomal recessive or X-linked. There are over 80 recognised primary immunodeficiency syndromes; they are generally grouped by the part of the immune system that is malfunctioning, such as lymphocytes or granulocytes.

The treatment of primary immunodeficiencies depends on the nature of the defect, and may involve antibody infusions, long-term antibiotics and (in some cases) stem cell transplantation.The characteristics of lacking and/or impaired antibody functions can be related to illnesses such as X-Linked Agammaglobulinemia and Common Variable Immune Deficiency

The incidence of Hodgkin's disease in the general population is about 10–30 per million person-years. This increases to 170 per million person-years in HIV positive patients.

Of all cancers involving the lymphocytes, 1% of cases are WM.

WM is a rare disorder, with fewer than 1,500 cases occurring in the United States annually. The median age of onset of WM is between 60 and 65 years, with some cases occurring in late teens.

Current medical treatments result in survival of some longer than 10 years; in part this is because better diagnostic testing means early diagnosis and treatments. Older diagnosis and treatments resulted in published reports of median survival of approximately 5 years from time of diagnosis. Currently, median survival is 6.5 years. In rare instances, WM progresses to multiple myeloma.

The International Prognostic Scoring System for Waldenström’s Macroglobulinemia (IPSSWM) is a predictive model to characterise long-term outcomes. According to the model, factors predicting reduced survival are:

- Age > 65 years

- Hemoglobin ≤ 11.5 g/dL

- Platelet count ≤ 100×10/L

- B2-microglobulin > 3 mg/L

- Serum monoclonal protein concentration > 70 g/L

The risk categories are:

- Low: ≤ 1 adverse variable except age

- Intermediate: 2 adverse characteristics or age > 65 years

- High: > 2 adverse characteristics

Five-year survival rates for these categories are 87%, 68% and 36%, respectively. The corresponding median survival rates are 12, 8, and 3.5 years.

The IPSSWM has been shown to be reliable. It is also applicable to patients on a rituximab-based treatment regimen. An additional predictive factor is elevated serum lactate dehydrogenase (LDH).

CVID has an estimated prevalence of about 1:50,000 in caucasians. The disease seems to be less prevalent amongst Asians and African-Americans. Males and females are equally affected; however, among children, boys predominate. A recent study of people in European with primary immunodeficiencies found that 30% had CVID, as opposed to a different immunodeficiency. 10-25% of people inherited the disease, typically through autosomal-dominant inheritance. Given the rarity of the disease, it is not yet possible to generalize on disease prevalence among ethnic and racial groups. CVID shortens the life-span; the median age of death for men and women is 42 and 44 years old, respectively. Those people with accompanying disorders had the worst prognosis and those people with CVID only had frequent infections had the longest survival rates, with life expectancy almost equalling that of the general UK population. Additionally, people with CVID with one or more noninfectious complications have an 11 times higher risk of death as compared to people with only infections.

All people with ALPS have signs of lymphoproliferation, which makes it the most common clinical manifestation of the disease. The increased proliferation of lymphoid cells can cause the size of lymphoid organs such as the lymph nodes and spleen to increase (lymphadenopathy and splenomegaly, present in respectively over 90% and over 80% of patients). The liver is enlarged (hepatomegaly in 30 - 40% of patients).

Autoimmune disease is the second most common clinical manifestation and one that most often requires treatment. Autoimmune cytopenias: Most common. Can be mild to very severe. Can be intermittent or chronic. These include: Autoimmune hemolytic anemia, Autoimmune neutropenia, Autoimmune thrombocytopenia.

Other signs can affect organ systems similar to systemic lupus erythematosus (least common, affecting <5% of patients) Symptoms of the nervous system include: Autoimmune cerebellar ataxia; Guillain–Barré syndrome; transverse myelitis. Gastrointestinal signs like Autoimmune esophagitis, gastritis, colitis, hepatitis, pancreatitis can be found or (Dermatologic) Urticaria, (Pulmonary) bronchiolitis obliterans, (Renal) Autoimmune glomerulonephritis, nephrotic syndrome.

Another sign are cancers such as Hodgkin and non-Hodgkin lymphomas which appear to be increased, possibly due to Epstein–Barr virus-encoded RNA-positivity. Some carcinomas may occur. Unaffected family members with genetic mutations are also at an increased risk of developing cancer.

Treatment is most commonly directed at autoimmune disease and may be needed to treat bulky lymphoproliferation. First line therapies include corticosteroids (very active but toxic with chronic use), and IVIgG, which are not as effective as in other immune cytopenia syndromes.

Second line therapies include: mycophenolate mofetil (cellcept) which inactivates inosine monophosphate, most studied in clinical trials with responses varying (relapse, resolution, partial response). It does not affect lymphoproliferation or reduce DNTs, with no drug-drug interactions. This treatment is commonly used agent in patients who require chronic treatment based on tolerance and efficacy. It may cause hypogammaglobulinemia (transient) requiring IVIgG replacement.

Sirolimus (rapamycin, rapamune) which is a mTOR (mammalian target of rapamycin) inhibitor can be active in most patients and can in some cases lead to complete or near-complete resolution of autoimmune disease (>90%) With this treatment most patients have complete resolution of lymphoproliferation, including lymphadenopathy and splenomegaly (>90%) and have elimination of peripheral blood DNTs. Sirolimus may not be as immune suppressive in normal lymphocytes as other agents. Some patients have had improvement in immune function with transition from cellcept to rapamycin and it has not been reported to cause hypogammaglobulinemia. Hypothetically, Sirolimus may have lower risk of secondary cancers as opposed to other immune suppressants and requires therapeutic drug monitoring. It is the second most commonly used agent in patients that require chronic therapy. It is mostly well tolerated (though side effects include mucositis, diarrhea, hyperlipidemia, delayed wound healing) with drug-drug interactions. It has better activity against autoimmune disease and lymphoproliferation than mycophenolate mofetil and other drugs; however, sirolimus requires therapeutic drug monitoring and can cause mucositis. A risk with any agent in pre-cancerous syndrome as immune suppression can decreased tumor immunosurvellence. Its mTOR inhibitors active against lymphomas, especially EBV+ lymphomas. The Goal serum trough is 5-15 ng/ml and can consider PCP prophylaxis but usually not needed.

Other treatments may include drugs like Fansidar, mercaptopurine: More commonly used in Europe. Another is rituximab but this can cause lifelong hypogammaglobulinemia and a splenectomy but there is a >30% risk of pneumococcal sepsis even with vaccination and antibiotic prophylaxis

The current mortality is over 60% after 5 years. However, due to hematopoietic stem cell transplantation being performed only in recent years, this number could potentially be lowered in the future. In patients with CNS involvement, treatment with Interferon alpha at US National Cancer Institute resulted in complete remission in 90% of patients.

The disease is believed to be induced by a combination of Epstein Barr virus infection and immunosuppression through; immunosuppressive drugs (with case reports of methotrexate and azathioprine), infections such as HIV or chronic viral hepatitis or endogenous T-cell defects.

The prognosis is guarded with an overall mortality of 50%. Poor prognostic factors included HLH associated with malignancy, with half the patients dying by 1.4 months compared to 22.8 months for non-tumour associated HLH patients.

Secondary HLH in some individuals may be self-limited because patients are able to fully recover after having received only supportive medical treatment (i.e., IV immunoglobulin only). However, long-term remission without the use of cytotoxic and immune-suppressive therapies is unlikely in the majority of adults with HLH and in those with involvement of the central nervous system (brain and/or spinal cord).

Treatment with dose-adjusted EPOCH with rituximab has shown promising initial results in a small series of patients (n=17), with a 100% response rate, and 100% overall survival and progression-free survival at 28 months (median follow-up).

Current research is aimed at studying large cohorts of people with CVID in an attempt to better understand age of onset, as well as mechanism, genetic factors, and progression of the disease.

Funding for research in the US is provided by the National Institutes of Health. Key research in the UK was previously funded by the Primary Immunodeficiency Association (PiA) until its closure in January 2012, and funding is raised through the annual Jeans for Genes campaign. Current efforts are aimed at studying the following:

- Causes of complications. Little is known about why such diverse complications arise during treatment

- Underlying genetic factors. Though many polymorphisms and mutations have been identified, their respective roles in CVID development are poorly understood, and not represented in all people with CVID.

- Finding new ways to study CVID. Given that CVID arises from more than one gene, gene knock-out methods are unlikely to be helpful. It is necessary to seek out disease related polymorphisms by screening large populations of people with CVID, but this is challenging given the rarity of the disease.

HIV-SGD is more prevalent in HIV positive children than HIV positive adults, at about 19% and 1% respectively. Unlike other oral manifestations of HIV/AIDS such as Kaposi sarcoma, oral hairy leukoplakia and oral candidiasis, which decreased following the introduction of highly active antiretroviral therapy (HAART), HIV-SGD has increased.

Lymphoid leukemias — also called lymphocytic, lymphogenous, or lymphoblastic leukemias — are a group of leukemias affecting circulating lymphocytes, a type of white blood cells. The lymphocytic leukemias are closely related to lymphomas of the lymphocytes, to the point that some of them are unitary disease entities that can be called by either name (for example, adult T-cell leukemia/lymphoma). Such diseases are all lymphoproliferative disorders. Most lymphoid leukemias involve a particular subtype of lymphocytes, the B cells.

The cause of GS has not been discovered. The basic defect is most likely in the bone marrow and there is some evidence of autoimmune pathogenesis.

Clinically, PASLI disease is characterized by recurrent sinopulmonary infections that can lead to progressive airway damage. Patients also suffer from lymphoproliferation (large lymph nodes and spleen), chronic viremia due to EBV or CMV, distinctive lymphoid nodules at mucosal surfaces, autoimmune cytopenias, and EBV-driven B cell lymphoma. Importantly, the clinical presentations and disease courses are variable with some individuals severely affected, whereas others show little manifestation of disease. This “variable expressivity,” even within the same family, can be striking and may be explained by differences in lifestyle, exposure to pathogens, treatment efficacy, or other genetic modifiers.