The formal genetics of Fanconi's anemia were investigated on the basis of 21 
families from different European countries, and of 69 families from the 
literature.
CONCLUSIONS: 1. The result of segregation analysis is compatible with the 
hypothesis of a simple autosomal recessive mode of inheritance. 2. The number of 
sporadic cases is not greater than expected. 3. Among the affected siblings in 
the sibships analyzed, males are somewhat more frequent than females. However, 
this sex difference is also found among the unaffected siblings, and it is not 
statistically significant. 4. Contrary to assertions made in the literature, 
there is no clustering of affected in the sequence of siblings, no maternal age 
effect, and no preference of higher birth orders. 5. A high intrafamilial 
correlation for age at onset, and (very probably) number and severity of 
malformations points to genetic heterogeneity. Apart from the standard type, an 
especially mild type with late onset, few malformations, and a relatively benign 
course seems to exist. Its counterpart is possibly an especially severe type 
with early onset, many malformations, and a malignant course. However, definite 
conclusions on the special character of this heterogeneity will require 
application of additional methods.