Caused by certain nephritogenic strains of Group A streptococci .Complexes rest under the epithelium and induce proliferation of endothelium and mesangium .Most patients achieve complete recovery, though a small percentage of them has severe damage rapidly progressing to kidney failure .Otitis and sinusitisSinusitis refers to an inflammation of the mucosa lining the cavities that are within the facial bones .This illness frequently follows an extended infectious process that begins in the nasal mucosa .By contrast ,otitis media refers to an inflammatory condition of the middle ear cavity following an infection process in the upper airway extending from the nasopharynx .Although many viruses can cause infections in the airway associated to the respiratory system ,bacteria-caused infections have greater clinical importance .S. pneumoniae, H.influenzae and S.aureus are agents commonly found in middle ear and paranasal sinuses conditions .Laryngitis and epiglottitisViral infections affecting the upper respiratory tract can extend deeper to affect the larynx and trachea .Parainfluenza virus type I and III are the most common viruses forming colonies in and affecting the larynx ,though respiratory syncytial virus and influenza virus are also causing agents .Epiglottitis is found in infants ,it is commonly caused by H.influenzae virus dissemination from the nasopharynxWooping coughWooping cough or coqueluche is caused by infection with the Brudetella pertussis coccabacillus , which is spread through the air by respiratory droplets from an infected person .Microorganisms multiply only in association with ciliated epithelium and result in several virulence factors .After7 or 10 days ,the infection starts with a catarrh stage and low fever, rhinorrhea , profussion of lacrimal fluid and conjunctivitis . Cough progresses to severe paroxysms that end in strong inspiratory whoop .Acute bronchitisAcute bronchitis refers to inflammation of the bronchial mucosa .It generally follows serious infections of the upper respiratory airway as a complication of them,particularly infections caused by H. influenzae virus in the larynx of infants, and influenzae in children and adults .Cough is the most common symptom and treatment is frequently aimed at relieving symptoms .BronchiolitisBronchiolitis is a common illness of the lower respiratory airway of infants under the age of 1 year following inflammatory obstruction of the small airways in the lungs. Respiratory syncytial virus can account for more than 50%of cases,other viruses that can cause bronchiolitis include :parainfluinza III ,mycoplasma ,and some adenoviruses .The infection is generally transmitted by a family member suffering from a mild respiratory infection .The characteristic features of illness are obstruction of the bronchioles due to edema and accumulation of mucus and cell remains ,which results in air hyperinflation .Bacterial pneumoniaS.pneumoniae accounts for 25%to60% of acute bacterial pneumonia infections . Other common causing agent is H.influenzae virus (5%-15%) .The infection starts as an acute condition with fever and chills .It is frequently accompanied by pleural involvement and hemoptysis .During the first stage ,the alveoli are filled with edema fluid ,bacteria ,neutrophils and lysate erythrocytes (red hepatization) .The following stage includes neutrophils lysis and macrophages phagocytizing them (gray hepatization ),then ,resolution of the condition .Viral pneumonitisViruses can invade the lungs from the blood stream or directly through the airways .Many viral agents can cause pneumonia, including influenza ,parainfluenza and measles ,among others . At the beginning of the infection , the alveolar epithelium is affected and an interstitial mononuclear infiltrate is formed .Based on the sverity degree ,pneumonocyte I necrosis, or pneumonocyte II hyperplasia may occur .Pulmonary tuberculosisPrimary tuberculosis refers to the infection caused by Koch's bacillus to persons that have never been in touch with it before .Typically ,it induces Ghon complex ,a pulmonary condition that causes damage in the corresponding hilar lymph nodes .Frequently ,secondary tuberculosis results from bacilli reactivation or reinfection by exogenous bacilli .It generally affects adults and the most common symptom is coughing up blood .If the immune system suffers alterations ,bacteria may be miliary tuberculosis with very bad prognosis .I nfections caused by Streptococcus pneumoniaPneumococci commonly lodge in the upper respiratory tract , and may become invasive pathogens .About 90% of infants between the age of 6 months and 4,5 years carry S .pneumoniae at some stage of their life .S .pneumoniae is the most frequent cause of pneumonia and bacterial otitis media, and the third most frequent cause of meningitis .Infections caused by Haemophilus influenzaeThis pathogen is frequently endemic ,though it can cause outbreaks of the illness particularly in nursery schools and healthcare facilities for chronic patients H,influenzae type b accounts for almost 95% of the severe infections caused by encapsulated H.influenzae viruses (meningitis ,acute epiglottitis , pneumonia, septic arthritis ,cellulites ,osteomyelitis ,pericarditis ).Non encapsulated strains are etiologic agents of upper respiratory tract infection ,such as acute otitis media .