The pathway dysfunction of each specific enzyme causes a unique pattern of abnormally elevated levels of porphyrins and/or their precursors to accumulate in tissues, and to be excreted in urine and stool clinical presentation depends on associated enzyme and mode of inheritance, and is often influenced by metabolic and environmental factors clinically characterized by cutaneous or acute neuropsychiatric symptoms and syndromes, or both cutaneous manifestation is typically cutaneous photosensitivity, which can be severe acute neuropsychiatric manifestations are most typically abdominal pain, constipation, dysesthesia, muscular paralysis, and respiratory failure (which can be fatal); attacks can be aborted by early administration of hemin latency is common and there can be asymptomatic or minimally symptomatic carriers some carriers only become symptomatic after exposure to an additional agent or factor capable of inducing disease expression classification (from most to least common type): porphyria cutanea tarda (includes hepatoerythropoietic porphyria, a very rare type of porphyria associated with hemolytic anemia) acute intermittent porphyria erythropoietic protoporphyria variegate porphyria hereditary coproporphyria congenital erythropoietic porphyria aminolevulinic acid dehydratase deficiency can also be categorized as: hepatic porphyrias (delta-aminolevulinic acid dehydratase deficiency porphyria, acute intermittent porphyria, variegate porphyria, hereditary coproporphyria, porphyria cutanea tarda), in which the excess porphyrin production occurs in the liver erythropoietic porphyrias (erythropoietic protoporphyria, congenital erythropoietic porphyria), in which excess porphyrin production occurs in the bone marrow can also be categorized as: acute porphyrias (delta-aminolevulinic acid dehydratase deficiency porphyria, acute intermittent porphyria, variegate porphyria, hereditary coproporphyria), which typically cause neuropsychiatric problems, often manifesting as a severe abdominal pain and are associated with excess production and excretion in urine of porphobilinogen and delta-aminolevulinic acid nonacute porphyrias (porphyria cutanea tarda, congenital erythropoietic porphyria, erythropoietic protoporphyria), in which porphobilinogen and delta-aminolevulinic acid are not produced in excess can also be categorized according to t. viagra soft tabs review order viagra canadian viagra without a doctor prescription viagra pills buy viagra without prescription viagra soft gel viagra canada side effects of viagra 20 mg viagra online cheap canada viagra 20 mg 2 compresse genuine viagra sales