Identification and metabolic profiling of patients with lysosomal acid lipase deficiency

Abstract

Lysosomal acid lipase (LAL), encoded by the LIPA gene, catalyzes the intracellular hydrolysis of cholesteryl esters and triglycerides in hepatocytes and macrophages. LIPA defects cause accumulation of these lipids in lysosomes. LAL deficiency (LAL D) presents and progresses as a continuum with dyslipidemia, hepatomegaly, and liver fibrosis. To improve the understanding of the genetic basis of LAL D, an underappreciated cause of dyslipidemia and cirrhosis, we studied DNA samples from patients with various phenotypes of dyslipidemia. Participants (N=1357) were identified by lipid profiles and screened for the common disease causing LIPA exon 8 skipping splice-site mutation (c.894G>A; p.Ser275_Gln298del; rs116928232). Six patients were heterozygous for this variant. Complete LIPA sequencing revealed a patient, subsequently confirmed to have LAL D, with a heterozygous frameshift mutation involving deletion of exon 4 (p.Gly77Valfs*17 c.230-106_c.428+541del). A family study revealed a sister with the same genotype and phenotype. Genetic, clinical, and lipoprotein profiles of these sisters plus 6 additional family members are reported. Profiles of 2 other LAL D patients monitored for 2 decades are presented. Cholesterol homeostasis was studied to investigate rates of cholesterol synthesis and absorption in 4 LAL D patients. High-density lipoprotein (HDL) subspecies were also analyzed. We used this LIPA sequencing strategy (detection of the relatively common exon 8 variant followed by complete gene sequencing to identify additional mutations) as a means to further elucidate the genetic basis of LAL D among individuals with a suggestive clinical phenotype.