Monoclonal Gammopathy (MG) Associated with Gaucher Disease (GD). Report of 16 Cases from the French Observatoire on Gaucher Disease (FROG Study).

In addition to its common bone and visceral manifestations GD is frequently associated with B cell proliferation leading possibly to MG. The objective of our study was to determine the frequency and presentation of MG in GD patients.

Material and methods. FROG is a cross-sectionnal epidemiological study on adult GD involving 64 French centers. Standard clinical, biological(including serum protein electrophoresis) and imaging data performed as part of usual management within the 3 previous years were collected at the time of a routine visit. In patients with suspected MG specific additionnal data were studied:immunofixation, dosage of immunoglobulins, bone marrow aspiration.

Results. From 05/2005 to 06/2006 seventy seven adult GD type 1(38 male,39 female;mean age 47.3 years, range 18 to 78 years) were included. Sixteen cases of MG(20.8%) were observed (10 male and 6 female;mean age 61.25 years, range 47 to 79 years). Mean age of 61 cases of GD without MG(43.8 years;range 18 to 70 years)was significantly lower(p<0.0001). Thirteen cases(17%)were classified as MGUS and 3 (3.8%) as B cell malignancy:1 multiple myeloma, 1 Chronic Lymphocytic Leukemia, 1 Non Hodgkin Lymphoma. In 3 cases MG and GD were diagnosed simultaneously. In 13 cases MG was diagnosed in the course of GD(mean interval 12.2 years;range 6.7 to 16 years). MG immunochemical typing revealed 75 % Ig G, 12.5 %Ig A, 12.5 %Ig M, 75 % Kappa and 25 % Lambda. We observed one biclonal gammopathy(IgG and IgA Kappa). One case of MGUS was associated with capillary leak syndrome. In two patients MG level decreased with enzyme replacement therapy.

Conclusion. Frequency of MG in GD observed in our study (20.8%)is largely higher than in general population (1%). Furthermore this frequency is higher than in previous series of GD. However in GD patients, as observed in general population, frequency of MG seems to be related to age as mean age of patients with MG is significantly higher than mean age of patients without MG. Finally these data assess the need of specific follow-up regarding the high frequency of MG and the risk of B cell malignancy in GD patients.