In addition, homozygous Rag2-R229Q/Enhanced green fluorescent protein (EGFP) mutant mice (hereafter Rag2 KI/EGFP), developed by Marrella and colleagues13, presented clinical and immunological phenotypes remarkably similar to human OS with severe alopecia, erythroderma, infiltration by T lymphocytes and eosinophils into the skin and gut, and complete absence of B cells. The gene discussed is RAG2; the disease is exfoliative dermatitis.