Rare Genetic Disorders of the Breathing Airways

Overview

Mucociliary clearance, in which mucus secretions are cleared from the breathing airways, is the primary defense mechanism for the lungs. Inhaled particles, including microbes that can cause infections, are normally entrapped in mucus on the airway surfaces and then cleared out by the coordinated action of tiny hair-like structures called cilia. Individuals with primary ciliary dyskinesia, variant cystic fibrosis, and pseudohypoaldosteronism have defective mucociliary clearance. The purpose of this study is to collect clinical and genetic information about these three airway diseases to improve current diagnostic procedures.

Two types of genetic diseases are associated with abnormal mucociliary clearance. The first type results in defective ciliary function and includes primary ciliary dyskinesia (PCD), also known as Kartagener Syndrome. The second type results in defective ion transportation and includes variant cystic fibrosis (CF) and pseudohypoaldosteronism (PHA). The clinical manifestations of these three diseases overlap, and current evaluation procedures are inadequate for an accurate and timely diagnosis. A delayed diagnosis, coupled with poorly defined disease categories, results in sub-optimal treatment regimens. The purpose of this study is to better define the clinical and genetic features of PCD, variant CF, and PHA to develop improved diagnostic procedures. The study will also compare prevalence and age-related information among the three diseases and classic CF. Outcomes of this study may lead to improved clinical care and novel therapeutic approaches for rare genetic disorders of the airways. Prior to study entry, previous clinical data on all participants will be reviewed to ensure that individuals do not have common variants of asthma. In some cases, further clinical evaluation (sweat chloride testing, immunodeficiency testing, and a high-resolution computed tomography scan) may be recommended. Eligible participants will attend an initial six-hour study visit similar to a standard diagnostic evaluation. The participant's medical history will be reviewed and a physical examination will include height, weight, and vital sign measurements. Respiratory cultures, nasal samples, and blood will be collected. Non-invasive techniques will be used to measure oxyhemoglobin saturation levels and airflow; a chest x-ray will be required if none has been done in the last six months. If a firm diagnosis of PCD or variant CF has not been established after completion of the first study visit, the participant may return for additional visits. Salivary and semen samples may be collected from some individuals. A sweat chloride test and nasal potential difference test may also be performed.