Patients with disorders such as Down syndrome, sickle cell disease, neurofibromatosis type 1 (NF-1), and microcephalic osteodysplastic primordial dwarfism type II (MOPD II) have a higher incidence of MM angiopathy, collectively termed MM syndrome (MMS) (Scott and Smith 2009). This evidence concerns the gene NF1 and microcephalic osteodysplastic primordial dwarfism type II.