Relative prevalences of 11 complementation groups in FA. Results are based on the first 241 FA families classified by the European Fanconi Anemia Research Programme (1994-2003). This number includes the reference cell lines for groups A, B, C, D1, and D2 (Table 3). The absolute numbers per group were as follows: A, 159; B, 2; C, 23; D1, 8; D2, 8; E, 6; F, 5; G, 21; I, 4; J, 4; L, 1.