Genetics
Inherited mutations in the UROD gene cause about 20% of cases (the other 80% of cases do not have mutations in UROD, and are classified as sporadic). UROD makes an enzyme called uroporphyrinogen III decarboxylase, which is critical to the chemical process that leads to heme production. The activity of this enzyme is usually reduced by 50% in all tissues in people with the inherited form of the condition.Nongenetic factors such as excess iron or partially genetic factors such as alcohol use disorder and others listed above can increase the demand for heme and the enzymes required to make heme. The combination of this increased demand and reduced activity of uroporphyrinogen decarboxylase disrupts heme production and allows byproducts of the process to accumulate in the body, triggering the signs and symptoms of porphyria cutanea tarda.The HFE gene makes a protein that helps cells regulate the absorption of iron from the digestive tract and into the cells of the body. Certain mutations in the HFE gene cause hemochromatosis (an iron overload disorder). People who have these mutations are also at an increased risk of developing porphyria cutanea tarda.In the 20% of cases where porphyria cutanea tarda is inherited, it is inherited in an autosomal dominant pattern, which means one copy of the altered gene is sufficient to decrease enzyme activity and cause the signs and symptoms of the disorder.
Contraindications
Hypersensitivity

Society and culture
Availability
Gatifloxacin is currently available in the US and Canada only as an ophthalmic solution.In 2011, the Union Health and Family Welfare Ministry of India banned the manufacture, sale, and distribution of gatifloxacin because of its adverse side effects.In China, gatifloxacin is sold in tablet as well as in eye drop formulations. Brand names
Bristol-Myers Squibb introduced gatifloxacin in 1999 under the proprietary name Tequin for the treatment of respiratory tract infections, having licensed the medication from Kyorin Pharmaceutical Company of Japan. Allergan produces it in eye-drop formulation under the names Zymar, Zymaxid and Zylopred. In many countries, gatifloxacin is also available as tablets and in various aqueous solutions for intravenous therapy. == References ==