Chronic bronchitis
Chronic bronchitis is a lower respiratory tract disease, defined by a productive cough that lasts for three months or more per year for at least two years. The cough is sometimes referred to as a smokers cough since it often results from smoking. When chronic bronchitis occurs together with decreased airflow it is known as chronic obstructive pulmonary disease (COPD). Many people with chronic bronchitis have COPD however, most people with COPD do not also have chronic bronchitis. Estimates of the number of people with COPD who have chronic bronchitis are 7 to 40%. Estimates of the number of people who smoke and have chronic bronchitis who also have COPD is 60%.The term "chronic bronchitis" was used in previous definitions of COPD but is no longer included in the definition. The term is still used clinically. While both chronic bronchitis and emphysema are often associated with COPD, neither is needed to make the diagnosis. A Chinese consensus commented on symptomatic types of COPD that include chronic bronchitis with frequent exacerbations.Chronic bronchitis is marked by mucus hypersecretion and mucins. The excess mucus is produced by an increased number of goblet cells, and enlarged submucosal glands in response to long-term irritation. The mucous glands in the submucosa secrete more than the goblet cells. Mucins thicken mucus, and their concentration  has been found to be high in cases of chronic bronchitis, and also to correlate with the severity of the disease.
Signs and symptoms
The failure of the metanephros to develop in cases of BRA and some cases involving unilateral renal agenesis (URA) is due primarily to the failure of the mesonephric duct to produce a ureteric bud capable of inducing the metanephric mesenchyme. The failed induction will thereby cause the subsequent degeneration of the metanephros by apoptosis and other mechanisms. The mesonephric duct(s) of the agenic kidney(s) will also degenerate and fail to connect with the bladder. Therefore, the means by which the fetus produces urine and transports it to the bladder for excretion into the amniotic sac has been severely compromised (in the cases of URA), or completely eliminated (in the cases of BRA). The decreased volume of amniotic fluid causes the growing fetus to become compressed by the mothers uterus. This compression can cause many physical deformities of the fetus, most common of which is Potter facies. Lower extremity anomalies are frequent in these cases, which often presents with clubbed feet and/or bowing of the legs..Sirenomelia, or "Mermaid syndrome" (which occurs approximately in 1:45,000 births) can also present. In fact, nearly all reported cases of sirenomelia also present with BRA.It is associated with childhood polycystic kidney disease which is autosomal recessive in origin Other anomalies of the classic Potter sequence infant include a parrot beak nose, redundant skin, and the most common characteristic of infants with BRA which is a skin fold of tissue extending from the medial canthus across the cheek.