Lysosomal Acid Lipase Deficiency in 23 Spanish Patients: High Frequency of the Novel c.966+2T>G Mutation in Wolman Disease

Twice weekly dosing with Sebelipase alfa (Kanuma®) rescues severely ill infants with Wolman disease

BACKGROUND

Sebelipase alfa (Kanuma®) is approved for patients with Wolman disease (WD) at a dosage of 3-5 mg/kg once weekly. Survival rates in the second of two clinical trials was greater, despite recruiting more severely ill patients, probably related to higher initial and maximal doses. We aimed to evaluate the effective pharmacokinetics and pharmacodynamics of Sebelipase alfa when administered to patients with severe WD at 5 mg/kg twice weekly, an intensive regimen which was not assessed in the trials.

METHODS

We recruited 3 patients receiving Sebelipase alfa 5 mg/kg twice weekly. We measured LAL activity in leukocytes and plasma oxysterol concentration in two patients and LAL activity in fibroblasts in one patient. Clinical follow up was also assessed.

RESULTS

Analyses of LAL activity and oxysterols demonstrate that there is short-lived enzyme activity post-dosing which is associated with the release of stored lipids. Clinical data demonstrate that 5 mg/kg twice weekly dosing is well tolerated and effective.

CONCLUSION

5 mg/kg twice weekly dosing with Sebelipase alfa rescues severely ill infants with WD by increasing substrate clearance. There is biologically relevant lipid accumulation in the 'trough' periods before the next dosing, even with this intensive regimen.

First LIPA Mutational Analysis in Egyptian Patients Reveals One Novel Variant: Wolman Disease

Lysosomal acid lipase (LAL) is a necessary enzyme for the hydrolysis of both triglycerides (TGs) and cholesteryl esters (CEs) in the lysosome. Deficiency of this enzyme encoded by the lipase A (LIPA) gene leads to LAL deficiency (LAL-D). A severe disease subtype of LAL-D is known as Wolman disease (WD), present with diarrhea, hepatosplenomegaly, and adrenal calcification. Untreated patients do not survive more than a year. The aim of this study was to assess the clinical and molecular characterizations of WD patients in Egypt. A total of seven patients (from five unrelated Egyptian families) were screened by targeted next-generation sequencing (NGS), and the co-segregation of causative variants was analyzed using Sanger sequencing. Furthermore, multiple in silico analyses were performed to assess the pathogenicity of the candidate variants. Overall, we identified three diseases causing variants harbored in the LIPA gene. One of these variants is a novel missense variant (NM_000235.4: c.1122 T > G; p. His374Gln), which was classified as a likely pathogenic variant. All variants were predicted to be disease causing using in silico analyses. Our findings expand the spectrum of variants involved in WD which may help to investigate phenotype-genotype correlation and assist genetic counseling. To the best of our knowledge, this is the first clinico-genetic study carried out on Egyptian patients affected with WD.

A Novel Variant in the LIPA Gene Associated with Distinct Phenotype

Deficiency of lysosomal acid lipase (LAL-D) is caused by biallelic pathogenic variants in the LIPA gene. Spectrum of LAL-D ranges from early onset of hepatosplenomegaly and psychomotor regression (Wolman disease) to a more chronic course (cholesteryl ester storage disease - CESD). The diagnosis is based on lipid and biomarker profiles, specific liver histopathology, enzyme deficiency, and identification of causative genetic variants. Biomarker findings are a useful for diagnostics of LAL-D, including high plasma concentration of chitotriosidase as well as elevated oxysterols. Current treatment options include enzyme replacement therapy (sebelipase-alpha), statins, liver transplantation, and stem cell transplantation. We present two pairs of siblings from Serbia with a distinctive phenotype resembling LAL-D with a novel variant of unknown significance (VUS) detected in the LIPA gene and residual LAL activity. All patients presented with hepatosplenomegaly at early childhood. In siblings from family 1, compound heterozygosity for a pathogenic c.419G>A (p.Trp140Ter) variant and a novel VUS c.851C>T (p.Ser284Phe) was detected. Patients from family 2 were homozygous for c.851C>T VUS and both have typical histopathologic findings for LAL-D in the liver. Enzyme activity of LAL was tested in three patients and reported as sufficient, and therefore enzyme replacement therapy could not be approved. When confronted with a challenge of diagnosing an inherited metabolic disorder, several aspects are taken into consideration: clinical manifestations, specific biomarkers, enzyme assay results, and molecular genetic findings. This report brings cases to light which have a considerable discrepancy between those aspects, namely the preserved LAL enzyme activity in presence of clinical manifestations and rare variants in the LIPA gene.

Large-scale screening of lipase acid deficiency in at risk population

BACKGROUND

Lysosomal acid lipase deficiency (LALD, OMIM#278000) is a rare lysosomal disorder with an autosomal recessive inheritance. The main clinical manifestations are related to a progressive accumulation of cholesteryl esters, triglycerides or both within the lysosome in different organs such as the liver, spleen, and cardiovascular system. A wide range of clinical severity is associated with LALD including a severe very rare antenatal/neonatal/infantile phenotype named Wolman disease and a late-onset form named cholesteryl ester storage disease (CESD).

METHODS

This study aimed to investigate a cohort of at-risk patients (4174) presenting with clinical or biological signs consistent with LALD using the assessment of LAL activity on dried blood spots.

RESULTS

LAL activity was lower than 0.05 nmol/punch/L (cut-off: 0.12) in 19 patients including 13 CESD and 6 Wolman. Molecular study has been conducted in 17 patients and succeeded in identifying 34 mutated alleles. Fourteen unique variants have been characterized, 7 of which are novel.

CONCLUSION

This study allowed to identify a series of patients and expanded the molecular spectrum knowledge of LALD. Besides, a new screening criteria grid based on the clinical/biological data from our study and the literature has been proposed in order to enhance the diagnosis rate in at risk populations.

Large-scale functional LIPA variant characterization to improve birth prevalence estimates of lysosomal acid lipase deficiency

Lysosomal acid lipase (LAL) deficiency is an autosomal recessive disorder caused by LIPA gene mutations that disrupt LAL activity. We performed in vitro functional testing of 149 LIPA variants to increase the understanding of the variant effects on LAL deficiency and to improve disease prevalence estimates. Chosen variants had been reported in literature or population databases. Functional testing was done by plasmid transient transfection and LAL activity assessment. We assembled a set of 165 published LAL deficient patient genotypes to evaluate this assay's effectiveness to recapitulate genotype/phenotype relationships. Rapidly progressive LAL deficient patients showed negligible enzymatic activity (<1%), whereas patients with childhood/adult LAL deficiency typically have 1-7% average activity. We benchmarked six in silico variant effect prediction algorithms with these functional data. PolyPhen-2 was shown to have a superior area under the receiver operating curve performance. We used functional data along with Genome Aggregation Database (gnomAD) allele frequencies to estimate LAL deficiency birth prevalence, yielding a range of 3.45-5.97 cases per million births in European-ancestry populations. The low estimate only considers functionally assayed variants in gnomAD. The high estimate computes allele frequencies for variants absent in gnomAD, and uses in silico scores for unassayed variants. Prevalence estimates are lower than previously published, underscoring LAL deficiency's rarity.

A Novel Mutation c.153 C>A in a Tunisian Girl With Wolman Disease and Unusual Presentation: Hemophagocytic Lymphohistiocytosis

Wolman disease is an ultrarare lysosomal storage disease caused by a mutation in the LIPA gene. The clinical features of Wolman disease include early onset of vomiting, diarrhea, failure to thrive, hepatosplenomegaly, and bilateral adrenal calcification. We report the case of a 3-month-old infant who presented clinical features of hemophagocytic lymphohistiocytosis. Genetic sequence analysis of the LIPA gene revealed homozygous mutation c.153 C>A (p.Tyr51*). The parents were heterozygous for this mutation. Prenatal diagnosis has been carried out in the next pregnancy. To our knowledge, this mutation has never been reported before, and this is an unusual case of secondary hemophagocytic lymphohistiocytosis complicating Wolman disease.

Early onset lysosomal acid lipase deficiency presenting as secondary hemophagocytic lymphohistiocytosis: Two infants treated with sebelipase alfa

Two unrelated infants were diagnosed with and initially treated for hemophagocytic lymphohistiocytosis (HLH), but progressed to cholestasis and liver failure. Early onset lysosomal acid lipase deficiency (EO-LAL-D) was suspected due to lymphocytes with cytoplasmic vacuolation and/or adrenal calcifications and confirmed by enzymatic and genetic analysis. Enzyme replacement therapy with sebelipase alfa was implemented, but both children died, despite initial improvement. Since this inborn error of metabolism progresses rapidly in infants, early diagnosis is crucial, and appropriate treatment should be started as soon as possible. The authors suggest that the diagnosis of EO-LAL-D should be considered in infants with symptoms of HLH.

Molecular and clinical characterization of a series of patients with childhood-onset lysosomal acid lipase deficiency. Retrospective investigations, follow-up and detection of two novel LIPA pathogenic variants

BACKGROUND AND AIMS

Childhood/Adult-onset Lysosomal Acid Lipase Deficiency (LAL-D) is a recessive disorder due to loss of function variants of LAL, the enzyme which hydrolyses cholesteryl esters, derived from internalized apoB containing lipoproteins. The disease is characterized by multi-organ involvement including the liver, spleen, intestine and cardiovascular system. The aim of this study was the clinical and molecular characterization of 14 (13 unrelated) previously unreported patients with childhood-onset LAL-D.

METHODS

Data collected included clinical and laboratory investigations, liver imaging, liver biopsy and LIPA gene analysis. The response to lipid-lowering medications, liver transplantation and enzyme replacement therapy (ERT) was reported for some patients.

RESULTS

LAL-D was suspected at 4.4 ± 3.3 years of age for the presence of hepatomegaly, elevated serum transaminases and hypercholesterolemia, and was confirmed by liver biopsy/imaging and LAL assay. The follow up period ranged from 3 to 40 years (mean 7.8 ± 4.0 years in 13 cases). Patients treated with statins with or without ezetimibe showed 28% reduction of plasma LDL-cholesterol without a tangible effect on liver enzymes; some patients receiving ERT showed normalized lipoprotein profile and transaminase levels. The common c.894G > A variant was observed in homozygosity or compound heterozygosity in 10 patients. We found seven previously reported variants: p.(Trp140*), p.(Arg218*), p.(Gly266*), p.(Thr288Ile), p.(Leu294Ser), p.(His295Tyr) and p.(Gly342Arg) and two novel variants: p.(Asp345Asn), affecting the LAL catalytic triad, and c.229+3A > C, affecting splicing. Homozygosity for p.(Thr288Ile) or c.229+3A > C was associated with a severe phenotype.

CONCLUSIONS

This study provides additional data on the features of childhood-onset LAL-D and describes two novel pathogenic variants of the LIPA gene.

The role of sebelipase alfa in the treatment of lysosomal acid lipase deficiency

Lysosomal acid lipase deficiency (LALD) is a lysosomal storage disorder (LSD) characterized either by infantile onset with fulminant clinical course and very poor prognosis or childhood/adult-onset disease with an attenuated phenotype. The disorder is often misdiagnosed or remains undiagnosed in children and adults due to a rather unspecific clinical presentation with dyslipidemia and steatohepatitis. Until recently, no good treatment options were available for LALD. Despite supportive and symptomatic therapies, death occurred before 1 year of age in patients with infantile-onset disease and patients with childhood/adult-onset LALD suffered from significant complications, such as liver cirrhosis, requiring liver transplantation and early-onset cardiovascular disease. With the recent approval of sebelipase alfa for clinical use in infantile- as well as childhood/adult-onset LALD, a new treatment era for this disorder has begun. Sebelipase alfa is a recombinant human lysosomal acid lipase (LAL), which is administered via the intravenous route. Clinical trials have shown significant improvement of disease parameters such as liver transaminases, hepatomegaly, and dyslipidemia in childhood/adult-onset LALD patients. Treatment of infants with the severe infantile-onset form of the disease has led to improved survival beyond the age of 1 year, and also showed improvement of hepatic and gastrointestinal symptoms, as well as growth. Overall, sebelipase alfa has a favorable safety profile and promises to be a good long-term treatment option for patients with LALD, with significant reduction of disease burden and increased life expectancy.