HEP is extremely rare, it is caused by low levels of the same enzyme that causes PCT, UROD. In Familial PCT, there is only one changed copy of the UROD gene, the other copy is normal. In HEP both copies of the UROD gene have changes. The symptoms of HEP resemble CEP, with skin blistering that usually starts in infancy or early childhood. HEP is a much more severe form of PCT.
Skin photosensitivity (sun sensitivity) in HEP results in severe blistering and scarring. Increased hair growth (hypertrichosis) on sun-exposed skin, and reddish-colored urine due to the high levels of porphyrins are common.
The standard treatments for PC (regularly scheduled phlebotomies or low doses of hydroxychloroquine), are generally less effective in HEP but can still be tried.
People with HEP should see a porphyria specialist at least once a year for regular follow-up.
The main way to manage symptoms of HEP is avoidance and/or protection from sunlight.
HEP is an autosomal recessive condition. Autosomal means that the defect is not on the chromosomes that determine sex, and recessive means that patients who have HEP have inherited two changed copies of the UROD gene, one from each of their parents. When someone with HEP has children, all their children will have Familial PCT since they will inherit one copy of the changed UROD gene. The children will not necessarily develop symptoms of PCT but should have genetic counseling.