Background: Nontuberculous mycobacteria (NTM) are ubiquitous environmental organisms that have been increasingly associated with human disease, commonly involving the lung. Post menopausal Caucasian women seem particularly predisposed to the development of peripheral nodules and dilated airways (bronchiectasis) associated with these organisms. These women have distinguishing body characteristics of being taller and thinner than age and gender matched controls yet have no identifiable systemic immune defects. There is, however, considerable overlap with genetic disorders of mucociliary clearance such as cystic fibrosis (CF) and primary ciliary dyskinesia (PCD). The Genetic Diseases of Mucociliary Clearance Consortium (GDMCC) is one of 10 consortia in the Rare Diseases Clinical Research Network formed under the Office of Rare Diseases in collaboration with NCRR, NICHD, NINDS, NIAMS, NIDDK, NHLBI in response to the Rare Diseases Act of 2002. The GDMCC is comprised of 5 geographically-dispersed clinical research sites that are designed to study rare diseases which involve defects in clearance of mucus secretions from the airways (defective "mucociliary clearance"). These sites will collaborate in diagnostic, genetic, and other studies in patients with impairments of mucociliary clearance, including primary ciliary dyskinesia (PCD), variant cystic fibrosis (CF), and pseudohypoaldosteronism (PHA). These studies are also applicable to diseases where altered airways clearance may play a primary or contributory role such as nontuberculous mycobacterial lung disease, chronic granulomatous disease, and the hyper-IgE syndromes. Disorders such as PCD, CF, and PHA reflect genetic defects in airway host-defense, and typically result in chronic infection of the airways. Patients with these disorders of the conducting airways and sinuses have delayed (or incorrect) diagnoses, because diagnostic tests are not readily available. These patients may also have sub-optimal management of their clinical disease, because the cause of these disorders is not well-defined, and treatment regimens are usually not driven by evidence-based medicine.