Prevalence, clinical features, and prognosis of patients with extremely low high-density lipoprotein cholesterol

•Most patients exhibiting extremely low HDL cholesterol level had secondary causes.•Extremely low HDL cholesterol was associated with the poorest prognosis.•Extremely low HDL cholesterol was not always associated with cardiovascular disease.

BackgroundLittle data exist on the clinical features of patients with an extremely low level of high-density lipoprotein (HDL) cholesterol (<20 mg/dL).ObjectiveTo assess the clinical characteristics of Japanese patients with extremely low HDL cholesterol levels.MethodsIn this observational study of 429 patients with extremely low HDL cholesterol levels among 43,368 subjects whose HDL cholesterol was measured for any reason at Kanazawa University Hospital from April 2004 to March 2014, we investigated the presence of coronary artery disease, chronic kidney disease, the potential causes of reduced HDL cholesterol, their prognosis, and the cause of death.ResultsMost patients (n = 425, 99%) exhibited secondary causes, including malignancies (n = 157, 37%), inflammatory diseases (n = 219, 51%), or other critical situations, such as major bleeding (n = 58, 14%). During the median 175-day follow-up period, 106 patients died. The causes of death in 80 (75%) patients were malignancies, inflammatory diseases, or major bleeding, in contrast to a relatively low incidence of death from atherosclerotic cardiovascular disease (n = 10, 10%). Multiple regression analysis showed that the presence of malignancy and HDL cholesterol was independently associated with death, in addition to age. The cumulative survival curve revealed that patients with an HDL cholesterol of <15 mg/dl, determined using the receiver-operating characteristic curve, had significantly higher mortality than those whose HDL cholesterol level was ≥15 mg/dL.ConclusionsExtremely low HDL cholesterol levels could be a useful marker for poor prognosis, not necessarily related to cardiovascular diseases.