Lysosomal storage diseases: heterogeneous group of disorders

The patient journey of patients with Fabry disease, Gaucher disease and Mucopolysaccharidosis type II: A German-wide telephone survey

Background

Lysosomal Storage Diseases (LSD) are rare and multisytemic diseases which are caused by lysosomal enzyme deficiencies leading into accumulation of waste products due to an interruption in the decomposition process. Due to the low prevalence and therefore limited disease awareness as well as the fact that LSD patients present with unspecific symptoms the final diagnosis is often made after a long delay. The aim of this German-wide survey was to characterize the period between onset of symptoms and final diagnosis regarding e.g. self-perceived health, symptom burden and false diagnoses for patients with selected LSDs (Fabry disease (FD), Gaucher disease (GD) and Mucopolysaccharidosis type II (MPS II).

Methods

The study was conducted as a telephone based cross-sectional survey. All patients living in Germany with a confirmed diagnosis of FD, GD or MPS II were eligible to participate. The questionnaire was provided in advance in order to enable the participants to prepare for the interview. Only descriptive analyses were carried out. Single analyses were not carried out for all three patient groups due low case numbers.

Results

Of the overall population, 39 patients have been diagnosed with FD, 19 with GD and 11 with MPS II with the majority of patients being index patients. The majority of FD patients reported their current health status as “satisfactory” or better (79.5%). Self-perceived health status was observed to be at least stable or improving for the majority of FD patients compared to the year prior to diagnosis. The most frequently reported symptoms for patients with FD were paraesthesias (51.3%), whereas patients with GD reported a tendency for bleeding, blue spots or coagulation disorder (63.2%) as well as hepatomegaly and/or splenomegaly (63.2%) as the most commonly appearing symptoms. The number of patients reporting misdiagnoses was n = 5 (13.5%) for patients with FD and n = 5 (27.8%) for patients with GD. The median duration of the diagnostic delay was 21.0 years for FD, 20.0 years for GD and 2.0 years for MPS II.

Conclusions

This study showed that self-perceived status of health for patients might improve once the final correct diagnoses has been made and specific treatment was available. Furthermore, it was observed that diagnostic delay is still high in Germany for a relevant proportion of affected patients. Further challenges in the future will still be to increase awareness for these diseases across the entire healthcare sector to minimize the diagnostic delay.

Achievements and beyond: Scientific trajectory of Professor Mohammad A. Rafi

This biography highlights the scientific trajectory of Professor Mohammad A. Rafi, Ph.D., who, in particular, has greatly advanced the field of neurodegenerative disorders during his long and successful tenure at Jefferson Medical College, Thomas Jefferson University. This Editorial recognizes, above all, Professor Rafi's significant contributions to the study of lysosomal storage disorders as they relate to Krabbe Disease.

Enzyme replacement therapies: what is the best option?

Despite many beneficial outcomes of the conventional enzyme replacement therapy (ERT), several limitations such as the high-cost of the treatment and various inadvertent side effects including the occurrence of an immunological response against the infused enzyme and development of resistance to enzymes persist. These issues may limit the desired therapeutic outcomes of a majority of the lysosomal storage diseases (LSDs). Furthermore, the biodistribution of the recombinant enzymes into the target cells within the central nervous system (CNS), bone, cartilage, cornea, and heart still remain unresolved. All these shortcomings necessitate the development of more effective diagnosis and treatment modalities against LSDs. Taken all, maximizing the therapeutic response with minimal undesired side effects might be attainable by the development of targeted enzyme delivery systems (EDSs) as a promising alternative to the LSDs treatments, including different types of mucopolysaccharidoses ( MPSs ) as well as Fabry, Krabbe, Gaucher and Pompe diseases.

Lysosomal Re-acidification Prevents Lysosphingolipid-Induced Lysosomal Impairment and Cellular Toxicity

Neurodegenerative lysosomal storage disorders (LSDs) are severe and untreatable, and mechanisms underlying cellular dysfunction are poorly understood. We found that toxic lipids relevant to three different LSDs disrupt multiple lysosomal and other cellular functions. Unbiased drug discovery revealed several structurally distinct protective compounds, approved for other uses, that prevent lysosomal and cellular toxicities of these lipids. Toxic lipids and protective agents show unexpected convergence on control of lysosomal pH and re-acidification as a critical component of toxicity and protection. In twitcher mice (a model of Krabbe disease [KD]), a central nervous system (CNS)-penetrant protective agent rescued myelin and oligodendrocyte (OL) progenitors, improved motor behavior, and extended lifespan. Our studies reveal shared principles relevant to several LSDs, in which diverse cellular and biochemical disruptions appear to be secondary to disruption of lysosomal pH regulation by specific lipids. These studies also provide novel protective strategies that confer therapeutic benefits in a mouse model of a severe LSD.