Hereditary spherocytosis is caused by a mutation in any one of five different genes. The table below shows the code for each gene, the protein that gene normally produces and the location of that gene in the genome (the first number tells you the chromosome).
For any one of these genes, there are a number of different mutations that can cause spherocytosis. These genes and proteins are discussed in more depth in the article The genetics of hereditary spherocytosis.
Genetic tests are rarely carried out because knowing the precise genetic mutation that has caused the spherocytosis has no implications for treatment. It may be useful, however, to determine whether the spherocytosis is dominant or recessive, when that is not clear from a family history.
For more information on the difference in pattern of inheritance for dominant and recessive genes see the article Chance of children inheriting hereditary spherocytosis.