Immunodeficiency-associated lymphoid proliferations (ALPS, HIV, and KSHV/HHV8).

The World Health Organization recognizes four categories of immunodeficiency-associated lymphoproliferative disorders (ID-LPDs): (1) lymphoproliferative diseases associated with primary immune disorders, (2) lymphomas associated with HIV infection, (3) post-transplant LPDs, and (4) other iatrogenic immunodeficiency-associated LPDs. Although these lesions are heterogeneous, due to their various underlying causes, they share several features, including frequent involvement of extranodal sites, diffuse aggressive histology, B-cell lineage, associated herpesvirus infection, and rapid clinical progression. The accurate diagnosis and treatment of the patients who develop immunodeficiency-associated LPDs often require careful evaluation of the morphology, immunophenotype, genotype, viral status, and clinical history. In this article, two of these four categories of ID-LPD are examined: lymphomas associated with HIV infections and lymphoproliferative diseases associated with primary immune disorders (PIDs), focusing on autoimmune lymphoproliferative syndrome (ALPS), as a representative disorder from this latter category.