What is CRIM status?
In Pompe disease (PD), a person has a change on both copies of their GAA gene. If both changes are severe, then their GAA genes are unable to make any normal acid maltase enzyme. A test of the skin (and possibly a blood test) can look at Cross Reactive Immunological Material (CRIM). If a person is CRIM positive, they make a little bit of acid maltase enzyme, whereas someone who is CRIM negative makes no acid maltase enzyme. This is important because when we replace the missing acid maltase enzyme with a man-made version called alglucosidase alfa or Lumizyme® in a person with no natural acid maltase enzyme, the body may recognize it as a foreign substance and develop antibodies to fight off the enzyme. When that happens, the body breaks down the enzyme before it can work to clear glycogen and makes the enzyme useless. However, there are now some medications that can be given to lower the immune response to Lumizyme and help it work better. Therefore, it is important to test babies with infantile Pompe disease to determine if they are CRIM positive (likely to respond well to treatment) or CRIM negative (likely to develop antibodies to treatment) before starting treatment. Everyone with late onset Pompe disease (LOPD) is CRIM positive because they have to have some natural enzyme to have developed symptoms later in life.
Pompe disease on Gene Reviews
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Stenger EO, Kazi Z, Lisi E, Gambello MJ, Kishnani P. Immune Tolerance Strategies in Siblings with Infantile Pompe Disease-Advantages for a Preemptive Approach to High-Sustained Antibody Titers. Mol Genet Metab Rep. 2015 Sep 1; 4:30-34.