They are at least a thousand times larger than the 1980 eruption of Mount St. Helens, which produced only 1 km3 (0.2 cu mi) of material, and at least six times larger than the 1815 eruption of Mount Tambora, the largest eruption in recent history, which produced 160 km3 (38 cu mi) of volcanic deposits.
Listen. 1  This severe homocystinuria is caused by rare MTHFR gene mutations (sometimes in combination with a second common MTHFR gene mutation). In severe MTHFR deficiency, signs and symptoms become apparent in infancy, however the condition can be milder, presenting in later childhood or adulthood.
1 Tests for both a urine and blood homocysteine may be used to help diagnose homocystinuria if a health practitioner suspects that an infant or child may have this inherited disorder. 2  In the U.S., all babies are routinely tested for excess methionine, a sign of homocystinuria, as part of their newborn screening. The homocysteine concentration may be elevated before B12 and folate tests are abnormal. 2  Some health practitioners may recommend homocysteine testing in malnourished individuals, the elderly, who often absorb less vitamin B12 from their diet, and individuals with poor nutrition, such as drug or alcohol addicts.