HAMP and hemochromatosis type 2: Nonetheless, in minor frequency, there are 4 additional disorders of primary iron overload: juvenile hemochromatosis (JH) or type 2 hemochromatosis, which is divided into 2 forms: type 2A JH, caused by mutations in the HJV gene on chromosome 1q21, and type 2B JH, caused by mutations in the HAMP gene on chromosome 19q13.