Most types of Porphyria are inherited, usually from one or both of a persons parents.
This is due to a mutation in one of the genes that produce heme. They may be inherited in an autosomal dominant , autosomal recessive, or X-linked dominant manner.
I have Variegate Porphyria which is inherited, I have the R59W South African mutation, inherited in an autosomal dominant pattern, which means the defective gene is located on an autosome, and inheriting one copy of the defective gene from an affected parent is sufficient to cause the disorder.