Preliminary data has suggested interferon-gamma deficient pathways, presence of a cystic fibrosis gene mutation and alpha-1 antiproteinase gene mutations as possible predisposing factors for pulmonary disease development in immunocompetent patients without underlying lung disease[3,6] Of particular interest is the increasing incidence of MAC lung infections characterized by progressive parenchymal lung disease in middle aged and elderly women with no history of smoking or underlying lung disease[7]. The gene discussed is IFNG; the disease is lung disorder.