Preliminary Results of a Prospective Observational Study to Assess the Prevalence of Gaucher Disease in an Adult Population Affected By MGUS

INTRODUCTION: Gaucher disease (GD) is a rare, autosomal recessive genetic disorder. It is due to a deficiency of the lysosomal enzyme, glucocerebrosidase, which leads to an accumulation of its substrate, glucosylceramide, in tissue macrophage with damage to hematological, visceral, and skeletal organ systems.

Although GD has a continuous spectrum of severity, it is traditionally classified into three forms: type 1 (chronic; lacking early onset neuronopathy), type 2 (acute; with early onset neuronopathy),and type 3 (chronic; with early onsetneuronopathy).

Type 1GD accounts for more than 90% all GD patients. Its prevalence world-wide is 1 in 50,000-100,000 but it is as high as ~1 in 850 in individuals of Ashkenazi heritage.

Type 1 GD is frequently associated to monoclonal gammopathies; despite the emergence of theories advanced to explain these observations, the cause remains unknown.

OBJECTIVE: Aim of the ongoing observational study is to determine the prevalence of unrecognized type I GD in a selected Italian population with MGUS.

MATERIALS AND METHODS: From January 2018, dried blood spots (DBS) sample from patients with laboratory evidence of MGUS coming from five hematology units of Sicily and Calabria were collected and tested for the acid β-glucosidase enzyme activity.

The study was approved by the local institutional review board. All patients provided informed consent for the prospective collection of their data.

In case of DBS positive result, a confirmatory test was carried over and, if GD was confirmed, the patient was referred to one of the Regional Reference Centers for Metabolic Disease, as for current clinical practice in Italy.

RESULTS: To date, 308 patients with MGUS were enrolled; acid β-glucosidase enzyme activity was low in 22 patients (7%). Sequence analysis of GBA gene was performed in these selected patients, but we have found only 4 patients with heterozygous mutation in the GBA1 gene, 1 homozygous(c.1226A>G -N370S) and 1 compound heterozygous (c.1226A>G -N370S and c.1448T>C -L444P); the last 2 patients had signs of GD (hepato-splenomegaly and mild thrombocytopenia).

CONCLUSIONS: Type 1 GD remains a rare lysosomal storage disorder but preliminary results of our observational study show that it should be considered in the diagnostic framework of patients with MGUS, particularly when other GD symptoms are present.