The finding of a PCC in a patient with a mutated SDHD (family 4 ) can be explained by an established genotype-phenotype association wherein there is a tendency for SDHD -nonsense mutation carriers to develop PCC, particularly when the mutation is in the 5’ portion of the gene, as in family 4 ( 34 , 35 ). The gene discussed is SDHD; the disease is adrenal gland pheochromocytoma.