Other
Symptoms, whether connected or not to GS, have been reported in a subset of those affected: fatigue (feeling tired all the time), difficulty maintaining concentration, unusual patterns of anxiety, loss of appetite, nausea, abdominal pain, loss of weight, itching (with no rash), and others, such as humor change or depression. But scientific studies found no clear pattern of adverse symptoms related to the elevated levels of unconjugated bilirubin in adults. However, other substances glucuronidized by the affected enzymes in those with Gilberts syndrome could theoretically, at their toxic levels, cause these symptoms. Consequently, debate exists about whether GS should be classified as a disease. However, Gilbert syndrome has been linked to an increased risk of gallstones. Cause
Mutations in the UGT1A1 gene lead to Gilbert Syndrome. The gene provides instructions for making the bilirubin uridine diphosphate glucuronosyltransferase (bilirubin-UGT) enzyme, which can be found in the liver cells and responsible for the removal of bilirubin from the body.The bilirubin-UGT enzyme performs a chemical reaction called glucuronidation. Glucuronic acid is transferred to unconjugated bilirubin, which is a yellowish pigment made when your body breaks down old red blood cells, and then being converted to conjugated bilirubin during the reaction. Conjugated bilirubin passes from the liver into the intestines with bile. Its then excreted in stool. People with Gilbert syndrome have approximately 30 percent of normal bilirubin-UGT enzyme function, which contributes to a lower rate of glucuronidation of unconjugated bilirubin. This toxic substance then accumulates in the body, causing mild hyperbilirubinemia.
Special populations
Primaquine has not been studied extensively in people 65 and older so it is not known if dosing should be adjusted for this population.Primaquine should not be administered to anyone with G6PD deficiency because a severe reaction can occur, resulting in hemolytic anemia. However, the WHO has recommended that a single dose of primaquine (0.25 mg/kg) is safe to give even in individuals with G6PD deficiency, for the purpose of preventing transmission of P. falciparum malaria.Primaquine is contraindicated in pregnancy, because the glucose-6-phosphate dehydrogenase status of the fetus would be unknown.Primaquine overdose can cause a dangerous reduction in various blood cell counts, and therefore should be avoided in people at risk for agranulocytosis, which include people with conditions such as rheumatoid arthritis and lupus erythematosus, and those taking concurrent medications that also decrease blood cell counts.Hemolytic reactions (moderate to severe) may occur in individuals with G6PD deficiency and in individuals with a family or personal history of favism. Areas of high prevalence of G6PD deficiency are Africa, Southern Europe, Mediterranean region, Middle East, South-East Asia, and Oceania. People from these regions have a greater tendency to develop hemolytic anemia (due to a congenital deficiency of erythrocytic G6PD) while receiving primaquine and related drugs.