Autoimmune Lymphoproliferative Syndrome: A Rare Cause of Disappearing HDL Syndrome

The term disappearing HDL syndrome refers to development of severe high density lipoprotein cholesterol (HDL-C) deficiencyin noncritically ill patients with previously normal HDL-C and triglyceride levels. Autoimmune lymphoproliferative syndrome(ALPS) is a disorder of the immune system due to an inability to regulate lymphocyte homeostasis resulting in lymphadenopathyand hepatosplenomegaly. We describe a 17-year-old boy who was evaluated in the lipid clinic for history of undetectable or lowHDL-C and low density lipoprotein cholesterol (LDL-C) levels.Past medical history was significant for ALPS IA diagnosed at 10years of age when he presented with bilateral cervical adenopathy. He was known to have a missense mutation in one allele of the FASprotein extracellular domain consistent with ALPS type 1A. HDL-C and LDL-C levels had been undetectable on multiple occasions,though lipids had not been measured prior to the diagnosis of ALPS. He had been receiving sirolimus for immunosuppression. TheHDL-C and LDL-C levels correlated with disease activity and improved to normal levels during times when the activity of ALPSwas controlled. This case highlights the importance of considering ALPS as a cause of low HDL-C and LDL-C levels in a child withevidence of lymphoproliferation