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.
Elevated homocysteine levels in the body do not cause any symptoms. 1  Elevated homocysteine levels affect the interior lining of blood vessels in the body, increasing the risk of atherosclerosis or narrowing of blood vessels. This can result in early heart attack and stroke.