RESUMEN
As hyperphosphorylated paratarg-7 (pP-7) carrier state was shown to be the first molecularly defined autosomal dominantly inherited risk factor for monoclonal gammopathy of unknown significance (MGUS) and multiple myeloma (MM) in a European population, the prevalence of pP-7 carrier state among African-Americans who have a significantly higher incidence of MGUS/MM is of interest. We therefore determined pP-7 carrier state and paraproteins with specificity for P-7 in African-American, European and Japanese patients with MGUS/MM and healthy controls. By isoelectric focusing and ELISA, a paratarg-7-specific paraprotein and the associated pP-7 carrier state was observed in 30/81 (37.0%) African-American, 42/252 (16.7%) European and 7/176 (4.0%) Japanese MGUS/MM patients (p < 0.001). A pP-7 carrier state was found in 11/100 (11.0%) African-American, 8/550 (1.5%) European and 1/278 (0.4%) Japanese healthy controls (p < 0.001), resulting in an odds ratio for MGUS/MM of 4.8 (p < 0.001) among African-American, 13.6 among European (p < 0.001) and 11.5 (p = 0.023) among Japanese carriers of pP-7. We conclude that pP-7 carriers are most prevalent among African-Americans, but a pP-7 carrier state is the strongest molecularly defined single risk factor for MGUS/MM known to date in all three ethnic groups. The high prevalence of pP-7 carriers among African-American patients emphasizes a predominant role of this genetic factor in the pathogenesis of these diseases. The large number of pP7 African-American patients and controls should facilitate the identification of the SNP or mutation underlying the pP-7 carrier state.