The diffusion of BLM has been measured to 1.34 
  
    
      
        
          
            
              
                
                  μ
                  m
                
                
                  2
                
              
              
                s
              
            
          
        
      
    
    {\displaystyle {\tfrac {\mathrm {\mu m} ^{2}}{\mathrm {s} }}}
   in nucleoplasm and 0.13  
  
    
      
        
          
            
              
                
                  
                    μ
                    m
                  
                  
                    2
                  
                
                
                  s
                
              
            
          
        
      
    
    {\displaystyle \textstyle {\tfrac {\mathrm {\mu m} ^{2}}{\mathrm {s} }}}
    at nucleoli  DNA helicases are enzymes that attach to DNA and temporarily unravel the double helix of the DNA molecule.
Bloom syndrome (often abbreviated as BS in literature) is a rare autosomal recessive genetic disorder characterized by short stature, predisposition to the development of cancer, and genomic instability. BS is caused by mutations in the BLM gene which is a member of the RecQ DNA helicase family. Mutations in other members of this family, namely WRN and RECQL4, are associated with the clinical entities Werner syndrome and Rothmund–Thomson syndrome, respectively. More broadly, Bloom syndrome is a member of a class of clinical entities that are characterized by chromosomal instability, genomic instability, or both and by cancer predisposition. Cells from a person with Bloom syndrome exhibit a striking genomic instability that includes excessive crossovers between homologous chromosomes and sister chromatid exchanges (SCEs). The condition was discovered and first described by New York dermatologist Dr. David Bloom in 1954.Bloom syndrome has also appeared in the older literature as Bloom–Torre–Machacek syndrome. Presentation
The most prominent feature of Bloom syndrome is proportional small size. The small size is apparent in utero. At birth, neonates exhibit rostral to caudal lengths, head circumferences, and birth weights that are typically below the third percentile.The second most commonly noted feature is a rash on the face that develops early in life as a result of sun exposure. The facial rash appears most prominently on the cheeks, nose, and around the lips. It is described as erythematous, that is red and inflamed, and telangiectatic, that is characterized by dilated blood vessels at the skins surface.