Bone manifestations in neuronopathic Gaucher disease while receiving high-dose enzyme replacement therapy

Neuronopathic Gaucher disease: Rare in the West, common in the East

Gaucher disease (GD) stands as one of the most prevalent lysosomal disorders, yet neuronopathic GD (nGD) is an uncommon subset characterized by a wide array of clinical manifestations that complicate diagnosis, particularly when neurological symptoms are understated. nGD may manifest as the acute neuronopathic type, or GD type 2 (GD2), either prenatally or within the first weeks to months of life, whereas GD type 3 (GD3) symptoms may emerge at any point during childhood or occasionally in adolescence. The clinical presentation encompasses severe systemic involvement to mild visceral disease, often coupled with a spectrum of progressive neurological signs and symptoms such as cognitive impairment, ataxia, seizures, myoclonus, varying degrees of brainstem dysfunction presenting with stridor, apneic episodes, and/or impaired swallowing. This manuscript aims to provide a comprehensive review of the incidence, distinctive presentations, and diverse clinical phenotypes of nGD across various countries and regions. It will explore the natural history of the neurodegenerative process in GD, shedding light on its various manifestations during infancy and childhood, and offer insights into the diagnostic journey, the challenges faced in the clinical management, and current and investigative therapeutic approaches for GD's neurological variants.

Changing clinical manifestations of Gaucher disease in Taiwan

BACKGROUND

Gaucher disease (GD) is a lysosomal storage disorder characterized by deficient glucocerebrosidase activity that results from biallelic mutations in the GBA1 gene. Its phenotypic variability allows GD to be classified into 3 subtypes based on the presence and extent of neurological manifestations. Enzyme replacement therapy (ERT) has been available for all patients with GD in Taiwan since 1998. Newborn screening (NBS) for GD has been available since 2015. This study attempted to unveil the clinical features of patients diagnosed with GD during different eras in Taiwan.

MATERIALS AND METHODS

Data from the health records of two tertiary hospitals responsible for two-thirds of the patients with GD in Taiwan were used. The study population included all patients identified as having GD between 1998, and April 2022, in these two hospitals for review. A total of 42 individuals were included, six of whom were diagnosed by NBS.

RESULTS

Our cohort presented a higher proportion of GD3 individuals, both by clinical suspicion and by NBS diagnosis, than that reported worldwide. The major subtypes that were recognized following NBS diagnosis were GD2 and GD3. The majority of GD patients carry at least one p.Leu483Pro variant. The 5-year survival rates were 0% for GD2 patients and 100% for patients with other subtypes. Patients diagnosed during the post-NBS era were free of symptoms on initial presentation, except for those with the GD2 subtype. For those diagnosed earlier, ERT was shown to be effective in terms of improved hemograms and prevented bone crises. However, the neurological symptoms in GD3 patients progressed despite ERT intervention.

CONCLUSION

ERT is essential in reversing the hematological presentations and preventing the skeletal complications of GD. Timely diagnosis of GD with NBS allows for early intervention with ERT to prevent disease progression and complications. However, the need for effective intervention for neurological dysfunction remains unmet.

Osteonecrosis in Gaucher disease in the era of multiple therapies: Biomarker set for risk stratification from a tertiary referral center

Background

A salutary effect of treatments for Gaucher disease (GD) has been a reduction in the incidence of avascular osteonecrosis (AVN). However, there are reports of AVN in patients receiving enzyme replacement therapy (ERT) , and it is not known whether it is related to individual treatments, GBA genotypes, phenotypes, biomarkers of residual disease activity, or anti-drug antibodies. Prompted by development of AVN in several patients receiving ERT, we aimed to delineate the determinants of AVN in patients receiving ERT or eliglustat substrate reduction therapy (SRT) during 20 years in a tertiary referral center.

Methods

Longitudinal follow-ups of 155 GD patients between 2001 and 2021 were analyzed for episodes of AVN on therapy, type of therapy, GBA1 genotype, spleen status, biomarkers, and other disease indicators. We applied mixed-effects logistic model to delineate the independent correlates of AVN while receiving treatment.

Results

The patients received cumulative 1382 years of treatment. There were 16 episodes of AVN in 14 patients, with two episodes, each occurring in two patients. Heteroallelic p.Asn409Ser GD1 patients were 10 times (95% CI, 1.5-67.2) more likely than p.Asn409Ser homozygous patients to develop osteonecrosis during treatment. History of AVN prior to treatment initiation was associated with 4.8-fold increased risk of AVN on treatment (95% CI, 1.5-15.2). The risk of AVN among patients receiving velaglucerase ERT was 4.68 times higher compared to patients receiving imiglucerase ERT (95% CI, 1.67-13). No patient receiving eliglustat SRT suffered AVN. There was a significant correlation between GlcSph levels and AVN. Together, these biomarkers reliably predicted risk of AVN during therapy (ROC AUC 0.894, p<0.001).

Conclusions

There is a low, but significant risk of AVN in GD in the era of ERT/SRT. We found that increased risk of AVN was related to GBA genotype, history of AVN prior to treatment initiation, residual serum GlcSph level, and the type of ERT. No patient receiving SRT developed AVN. These findings exemplify a new approach to biomarker applications in a rare inborn error of metabolism to evaluate clinical outcomes in comprehensively followed patients and will aid identification of GD patients at higher risk of AVN who will benefit from closer monitoring and treatment optimization.

Funding

LSD Training Fellowship from Sanofi to MB.

Current and emerging pharmacotherapy for Gaucher disease in pediatric populations

INTRODUCTION

The past decades have witnessed a remarkable improvement in the health of patients with Gaucher disease, the inherited deficiency of the lysosomal enzyme glucocerebrosidase, resulting from the availability of enzyme replacement and substrate reduction therapies. Especially in pediatric populations, early diagnosis and initiation of treatment is essential to achieving optimal outcomes.

AREAS COVERED

The authors review the literature pertaining to the effectiveness of currently available therapies and describe new pharmacotherapies under development, especially for young patients.

EXPERT OPINION

For pediatric patients with non-neuronopathic Gaucher disease, there may be new therapeutic options on the horizon in the form of gene therapy or small molecule glucocerebrosidase chaperones. These have the potential to result in a cure for systemic disease manifestations and/or to reduce the cost and convenience of treatment. For children with neuronopathic Gaucher disease, the challenge of targeting therapy to the central nervous system is being explored through new modalities including brain-targeted gene therapy, in-utero therapy, brain-penetrant small molecule chaperones, and other methods that convey enzyme across the blood-brain barrier. Indeed, these are exciting times for both pediatric patients with Gaucher disease and those with other lysosomal storage disorders.

Diagnosing neuronopathic Gaucher disease: New considerations and challenges in assigning Gaucher phenotypes

Gaucher disease (GD), resulting from biallelic mutations in the gene GBA1, is a monogenic recessively inherited Mendelian disorder with a wide range of phenotypic presentations. The more severe forms of the disease, acute neuronopathic GD (GD2) and chronic neuronopathic GD (GD3), also have a continuum of disease severity with an overlap in manifestations and limited genotype-phenotype correlation. In very young patients, assigning a definitive diagnosis can sometimes be challenging. Several recent studies highlight specific features of neuronopathic GD that may provide diagnostic clues. Distinguishing between the different GD types has important therapeutic implications. Currently there are limited treatment options specifically for neuronopathic GD due to the difficulty in delivering therapies across the blood-brain barrier. In this work, we present both classic and newly appreciated aspects of the Gaucher phenotype that can aid in discriminating between acute and chronic neuronopathic GD, and highlight the continuing therapeutic challenges.

Symmetric, bilateral upper and lower extremity lucent lesions in a patient with Gaucher's disease on enzyme replacement therapy

We report a case of a 6-year old girl with known type 3 Gaucher's Disease on enzyme replacement therapy who developed bilateral, symmetric osteolytic lesions in her humeri and femurs. While this manifestation of Gaucher's disease has been previously documented, it is an exceedingly rare variation. We observe that this patient shares 2 commonalities with 3 other patients reported in the literature to present with this phenotype. First, the patient's L444P/L444P genotype, present in approximately 11% of all Gaucher's patients, was also seen in these other patients. Second, like the other patients, this patient was treated with enzyme replacement therapy. It is unknown whether there is a correlation between these 2 independent variables and this rare phenotype, and further investigation may be warranted.