M. A. suffers from hypogammaglobulinemia that has been complicated by refractory Mycoplasma hominis septic arthritis. He has been receiving the antibiotic valnemulin under Emergency Investigational New Drug (eIND) 114686 following many prior treatments with standard antibiotics. M.A. has also been receiving intravenous immunoglobulin (IVIG) replacement. The antibiotic and IVIG have been helpful, but not sufficient for cure.