The authors have discovered that a specific mutation in the HNF4A gene causes Fanconi syndrome, where salt and protein loss by the kidneys leads to soft bones and short stature. People with this condition usually have to take tablets to replace the salts leaked by the kidneys, and the genes responsible haven’t been found until now. Previously mutations in HNF4A have been shown to cause young onset diabetes. This study shows that HNF4A mutations can cause kidney problems as well. This finding is also interesting because in this case the Fanconi syndrome is caused by a specific mutation called R76W, but not any other mutations in HNF4A. The function of HNF4A within the kidney is therefore dependent on this particular region within the gene. (By Dr Alexander Hamilton, http://jmg.bmj.com/content/early/2013/11/27/jmedgenet-2013-102066 )