Figure 2. Pedigree and genetic findings. The index patient and his youngest sister show a homozygous nonsense mutation, c.1003C>T/p.R335X, while both the father and one of the unaffected brothers are heterozygous for the mutation and the other unaffected brother does not carry the mutation. The sequencing electropherograms show the homozygous mutant sequence (top) in comparison with a wildtype control sequence (bottom).