MTHFR and amino acid metabolism disease: In storage disorders (e.g.,Niemann-Pick disease, Gaucher disease) and certain amino acid disorders (e.g.,methylenetetrahydrofolate reductase [MTHFR] deficiency, lysinuric proteinintolerance [LPI]) lower airway involvement may derive from accumulation of abnormalmetabolites and/or macrophages loaded with storage material in the airspaces andinterstitium, or from chronic airway aspiration associated with neuromotor delay[22–24].