LAL-D results from markedly reduced activity of lysosomal acid lipase, an enzyme that hydrolyzes cholesterol esters and triglycerides in the lysosomal compartment of cells. When enzyme activity is severely diminished or absent, these lipid substrates accumulate within lysosomes across a wide range of tissue types, producing progressive cellular and organ dysfunction. According to GeneReviews clinical data, the degree of residual enzyme activity is a central determinant of disease severity: pathogenic variants that completely abolish enzyme function are associated with the severe infantile-onset phenotype, while variants that permit some residual enzyme activity are associated with the later-onset, less severe forms of the condition. Specific causative genetic variants are not certified in this packet.

Consensus diagnostic guidelines for LAL-D have been published. According to GeneReviews, rapid diagnosis through biochemical and genetic testing is available. Enzymatic assay demonstrating markedly reduced lysosomal acid lipase activity constitutes the primary biochemical diagnostic approach. Characteristic lipid panel findings — including elevated triglycerides, elevated low-density lipoprotein cholesterol, and reduced high-density lipoprotein cholesterol — support the diagnosis in the childhood/adult-onset form. Elevated liver enzymes, including alkaline phosphatase and aminotransferases, are commonly observed. In the infantile form, adrenal gland calcification visible on imaging and liver biopsy demonstrating lipid-laden macrophages are characteristic findings. While newborn screening for LAL-D is technically feasible, as noted in GeneReviews, it had not been implemented in the United States as of the date of that chapter. Liver biopsy may also reveal microvesicular steatosis.

Sebelipase alfa (KANUMA) is FDA-approved for the treatment of lysosomal acid lipase deficiency, having received approval in December 2015 via the Biologics License Application pathway. It is the only certified approved treatment in this packet.

GeneReviews management guidance notes that while no cure exists for LAL-D, enzyme replacement therapy addresses the underlying enzyme deficiency. Published recommendations cover the management of both infantile-onset and childhood/adult-onset forms, though practice varies between countries and regions and multinational consensus clinical guidelines have not been established. Management in this condition addresses both the enzyme deficiency and its systemic consequences, including liver disease, dyslipidemia, gastrointestinal involvement, and growth failure in the infantile form. GeneReviews further notes that individuals with thrombocytopenia — a recognized complication in LAL-D — have specific considerations regarding nonsteroidal anti-inflammatory medications; this aspect of care is part of comprehensive management for the condition.

Prognosis in LAL-D is strongly determined by age of onset and degree of enzyme deficiency. According to GeneReviews, the infantile-onset form is rapidly progressive, with fatal liver failure in infancy among the most frequently documented outcomes in the severe phenotype in the absence of treatment. GeneReviews notes that early treatment is associated with better outcomes and that availability of enzyme replacement therapy has altered the natural history of this condition. In childhood- and adult-onset forms, the long-term course involves progressive liver disease — including hepatic fibrosis with potential progression to cirrhosis — along with sustained dyslipidemia. LAL-D is thought to be substantially underdiagnosed at the population level, which may affect the completeness of reported natural history data.

Research activity in LAL-D spans registry-based observational work, interventional studies, and early-phase translational research. Certified clinical trial records in this packet include an expanded newborn screening study that includes LAL-D (NCT03655223) and an ongoing LAL Deficiency Registry (NCT01633489, Alexion Pharmaceuticals) currently recruiting participants. GeneReviews additionally notes that a clinical trial is investigating in utero enzyme replacement therapy in lysosomal storage diseases including LAL-D (NCT04532047), and that preclinical gene therapy studies have been reported. The published research landscape is active, encompassing clinical descriptions, treatment outcomes, and laboratory investigation. LAL-D Aware provides patient community support resources.