SLE vs systemic lupus erythematosus

SLE

systemic lupus erythematosus

noun
  • A systemic autoimmune disease (or autoimmune connective tissue disease), where the immune system attacks the body's cells and tissue and causes inflammation and tissue damage. 

How often have the words SLE and systemic lupus erythematosus occurred in a corpus of books? (source: Google Ngram Viewer )