* Patients with primary ciliary dyskinesia (PCD) have trouble with clearing their bronchi from mucus, which in the long-term may produce severe damage to the lungs. Currently, there is no specific treatment for PCD beyond supportive measures such as airway hydration and postural drainage. * Glycine is an amino acid with anti-inflammatory properties that proved to be beneficial in another disease with problematic airway clearance, cystic fibrosis. * Magnesium participates in many crucial chemical reactions, including some that might favor fluidification and mobilization of mucus. Thiamine (vitamin B1) co-participates with magnesium in some mitochondrial enzymatic reactions occurring in the citric acid cycle. * Thus, oral supplements of glycine and magnesium+thiamine might improve symptoms and lung function of patients with PCD, and these effects may even be better if these supplements are combined. * In this study, in addition to their usual care, patients with PCD will receive for 6 months one of the following treatments: 1) an oral supplement of 0.5 g/kg/day glycine, 2) an oral supplement of up to 400 mg/day elementary magnesium plus up to 10 mg/day thiamine, according to the subject's age, 3) glycine plus magnesium+thiamine supplements, as described, or 4) a placebo, which is an inert substance. All treatments will be administered as a whitish powder contained in similar bottles. * The investigators will evaluate whether glycine and/or magnesium+thiamine reduce exacerbations of the disease, improve pulmonary function and quality of life, and reduce some pro-inflammatory compounds measured in saliva.