Methods
The records of all patients younger than 30 years with MM who were seen at the Mayo Clinic, Rochester, Minn, between January 1, 1956, and December 31, 1992, were reviewed.

Results
The frequency of MM in patients younger than 30 years who were seen at the Mayo Clinic was 0.3%. The clinical and laboratory features were typical of MM in 7 of the 10 patients. Two patients with no increase in bone marrow plasma cells had extensive extramedullary involvement, along with multiple skeletal lesions and the presence of an M protein in the serum and urine samples. One patient had multiple lytic lesions and 10% bone marrow plasma cells with no M component until 6 years after diagnosis, when a sacral plasmacytoma developed and an IgA- protein became apparent. Four patients had initial extramedullary involvement, 3 had renal insufficiency, and 2 had hypercalcemia. Osteolytic lesions were initially found in 6 patients. The M protein was light chain only in 5 patients and IgD in 2. Five patients responded to the initial conventional therapy, and 2 patients with primary resistant disease achieved long-lasting responses with high-dose therapy. The median duration of survival of the patients was 87 months. The proportion of patients who were predicted to be alive at 5 and 10 years was 69% and 31%, respectively.

Conclusions
In very young patients with MM, the presenting findings and the response to conventional therapy are similar to those in patients of all ages who have MM. However, a high proportion of patients had light-chain and IgD myeloma, and 2 patients with primary resistant disease achieved long-lasting responses with high-dose therapy. The survival of our patients was considerably longer than that of patients of all ages with MM.

Arch Intern Med. 1996;156:1463-1468