A U wave as seen on ECG. An electrocardiogram of an 18-year-old man showing U waves, most evident in lead V3. The U wave is a wave on an electrocardiogram that is not always seen. It is typically small, and, by definition, follows the T wave. U waves are thought to represent repolarization of the papillary muscles or Purkinje fibers.
HCP is caused by mutations in the CPOX gene, which codes for the enzyme coproporphyrinogen oxidase. This enzyme is responsible for the sixth step in the heme biosynthetic pathway, converting coproporphyrinogen III to protoporphyrinogen IX.
The risk of developing hereditary paraganglioma-pheochromocytoma types 1 and 2 is passed on only if the mutated copy of the gene is inherited from the father. The mechanism of this pattern of inheritance is unknown. The risk of developing types 3 and 4 can be inherited from the mother or the father.