Type 2B is caused by an autosomal dominant mutation in an unknown gene on chromosome 1 in the locus range of 1p21–1p13.3. The gene has been provisionally termed WS2B. Type 2C is caused by an autosomal dominant mutation in an unknown gene on chromosome 8 in the locus of 8p23. The gene has been provisionally termed WS2C. Type 2D is caused by an autosomal recessive mutation in both copies of the gene SNAI2. The study that discovered this association found that SNAI2 is activated by MITF as part of neural crest development, and this explained why mutations in MITF cause Waardenburg syndrome, as it results in a lack of activation of SNAI2. Mutations in a single copy of SNAI2 have also been found to cause patches of hair depigmentation (piebaldism) without any other symptoms. Type 2E is caused by an autosomal dominant mutation in the gene SOX10. Rarely, a mutation in a gene other than those currently known may be responsible for a Waardenburg syndrome with features of type 2. This is usually initially classified as simply type 2 but may be given its own subtype once a gene or locus is identified and established. Type 3 is caused by a mutation in the gene PAX3, the same gene as in type 1.
Conditions include:

Hypervitaminosis A
Hypervitaminosis D
Vitamin B3 § Toxicity
Megavitamin-B6 syndrome

Prevention
Prevention in healthy individuals not having any periods of avitaminosis or vitamin (vegetables) lack for 2 years at least is by not taking more than the expected normal or recommended amount of vitamin supplements. Epidemiology
In the United States, overdose exposure to all formulations of "vitamins" (which includes multi-vitamin/mineral products) was reported by 62,562 individuals in 2004 with nearly 80% of these exposures in children under the age of 6, leading to 53 "major" life-threatening outcomes and 3 deaths (2 from vitamins D and E; 1 from a multivitamin with iron). This may be compared to the 19,250 people who died of unintentional poisoning of all kinds in the U.S. in the same year (2004). In 2016, overdose exposure to all formulations of vitamins and multi-vitamin/mineral formulations was reported by 63,931 individuals to the American Association of Poison Control Centers with 72% of these exposures in children under the age of five. No deaths were reported. See also
Avitaminosis
Megavitamin therapy
Vitamin C megadosage

References
External links

Dietary reference intakes, official website.