Multiple Myeloma Is Exceptional in Paediatrics: Report of One Case From 1200 Patients in a Single Institution.

Abstract 4957

Multiple myeloma (MM), a disease usually observed in elderly patients, is extremely rare below 30 years of age. We present a case of a MM in a 10-year-old boy who has been admitted in September 2007 to the paediatric unit from the university hospital in Montpellier, with a fracture of his left femoral bone after a rugby match. In his history, he was known to present a juvenile myelomonocytic leukaemia (JMML) when he was 4-month-old in December 1998. For this diagnosis, he has been treated with aracytine and hydroxyurea for 4 years and he got a complete response (CR) since July 2005. At admission, surprisingly the radiography showed two lytic bone lesions. At MRI, it was found proximal and distal medullar metadiaphyseal spreading associated to a fracture, with no clinical symptom. The histology of the two tissue biopsies showed large dystrophic plasma cells, MI 15 positive with no clear evidence of a monoclonality by using light chain immunostaining. The bone marrow biopsy showed an interstitial infiltrate of dystrophic plasma cells, with only lambda light chain expression. Five percent of dystrophic plasma cells were observed on bone marrow smears. The monoclonal component IgG Lamda was 3.56 G/dL. Free kappa and lambda light chain dosages were respectively 5.65 mg/L and 766 mg/L, with a kappa lambda ratio under 0.01. Proteinuria was 0.64 g/day, haemoglobin was 106 G/L, and Beta2 microglobulin was 2.6mg/L. There was no hypercalcaemia and serum albumin and creatinin clearance were normal. Plasma cell labelling index (PCLI) was 1.16 % in the bone marrow and 6.6 circulating plasma cells/μL were counted in peripheral blood. Unfortunately, gene expression profiling analysis failed due to the low number of cells. PET scan found multiple uptakes in femoral, vertebral costal and sternal bones. So, this boy presented a multiple myeloma with stage IIIA according to Durie Salmon staging and ISS (International staging system) I. He underwent nine cycles of bortezomib (1.3 mg/m² D1, D4, D8, D11) and dexamethazone (40mg/D, D1 to D4) to reach a complete response. A myeloablative allogenic stem cell transplantation was performed from his sister the 11^th of September 2008, with a regimen based on cyclophosphamide (60mg/Kg, D1, D2) and TBI 12Gy. The immunosuppressive regimen associated methotrexate (D1, D3, D6) and cyclosporine. The graft contained 4.14 ×10⁸ MNC/kg, 4.19 10⁶ CD34/Kg and 6.16 10⁷ CD3/Kg. At Day 120, a full donor chimerism was obtained, with no GVHd, but the monoclonal component reappeared. He received only a single cycle of bortezomib and dexamethazone because of severe peripheral neuropathy and gastro-intestinal intolerance. A second CR has been obtained in June 2009. Minimal residual disease by flow cytometry will be soon performed in order to discuss donor lymphocyte infusions. We report a case of MM during the childhood that is extremely rare. Very few cases have been reported in the literature. In this particular case, the patient has been also treated for a JMML that may have a relationship with the MM. Unfortunately, no cytogenetic or DNA profiling has been performed. To our knowledge, it is the first time that such feature is reported. The overall survival (OS) reported by the Mayo clinic in a series of 10 children was 87 months that may suggests a better OS as compared to adults (Blade J, Kyle RA, Greipp PR. Multiple myeloma in patients younger than 30 years - Report of 10 cases and review of the literature. Arch Intern Med. 1996;156:1463-8).