Figure 1.

Genetic studies identify a shared mutation. (A–E) Pedigrees of informative families used for linkage analysis. (F) The combined parametric multipoint linkage analysis reveals a single significant peak with a maximum LOD score of 6.5 on chromosome 16. (G) Sequencing of the linked region reveals the presence of the mutation c.-167G>T in the promoter of PMM2 in all patients. Shown are electropherogram traces of the region c.-173_–c.161 from a patient homozygous for the mutation, a control (wild-type) subject, and a heterozygote parent.