Figure 4. A Swiss family with HSA R218P: genotyping, pedigree and thyroid function tests. A, Genotyping for the mutation HSA R218P. Results are aligned with each subject depicted on the pedigree in B. Amplification of a segment of the HSA gene containing the mutation with a mismatched oligonucleotide primer creates a new restriction site for Ava II only in the presence of the mutant nucleotide (CGC -> CCC). Affected subjects expressing proline 218 (CCC) show a 122 bp DNA fragment produced by enzymatic digestion of the mutant allele. Note that all affected subjects are heterozygous and that the 153 bp fragment amplified from DNA of the two normal subjects, expressing arginine 218 (CGC) only, resists enzymatic digestion. B, Pedigree of the family. Roman numerals indicate each generation and numbers below each symbol identify the subject. Individuals expressing the FDH phenotype are indicated by half filled symbols. C, Thyroid function tests. Results are aligned with each symbol. Values outside the normal range are in bold numbers. Note the disproportionate increase in serum T4 concentration as compared to that of T3 in the affected individuals. Subject I-1, a year old man, had diabetes mellitus with multiple organ complications and mild subclinical hypothyroidism, explaining the relatively lower serum T4 and T3 but not rT3 levels. [Adapted from Pannain et al (10)].