<prompt> A 3 month old child has moderate fever and non productive cough and mild dyspnea. After course of mild antibiotic the condition of the child improved transiently but he again develops high fever, productive cough and increased respiratory distress. Chest X ray shows hyperluscency and PFT shows obstructive pattern. Most probable diagnosis is ?Alveolar microlithiasisPost viral syndromeFollicular bronchitisBronchiolitis obliterans  <response>: Ans. is d i.e., Bronchiolitis obliterans Bronchiolitis obliterans o Bronchiolitis obliterans. is a rare chronic lung disease of the bronchioles and smaller airways. o Bronchiolitis obliterans most commonly occurs inpediatric population after respiratory infections i.e. adenovirus, mycoplasma, measles, influenza, peussis. o Other causes include connective tissue disease i.e. juvenile rheumatoid ahritis, systemic lupus erythematosis, scleroderma o Bronchiolitis occurs in all age groups. Pathogenesis o After the initial insult, inflammation affecting terminal bronchioles, respiratory bronchioles and alveolar ducts may result in obliteration of the airway lumen. o Epithelial damage resulting in abnormal repair is characteristic of bronchiolitis obliterans. Complete or paial obstruction of the airway lumen may result in air trapping or atelactasis. Clinical manifestations Cough, fever, cyanosis and respiratory distress followed by initial improvement may be the initial signs of bronchiolitis obliterans. o Progression of the disease may ensue with increasing dyspnoea, cough, sputum production and wheezing. o Chest radiographs may be relatively normal compared with the extent of physical findings but may demonstrate hyperluscency and patchy infiltrates occasionally, a swyer James syndrome, i.e. a unilateral hyperluscent lung has developed. o Pulmonary function tests demonstrate varaible findings but typically shows signs of airway obstruction. o Ventilation perfusion scan shows a typical motheaten appearance of multiple matched defects in ventilation and perfusion. o CT scan demonstrates patchy areas of hyperluscency. o Open lung biopsy or transbronchial biopsy remains the best means of establishing the diagnosis of bronchiolitis obliterans. Treatment o No definite therapy exists for bronchiolitis obliterans. o Administration of coicosteroids may be beneficial About other options Follicular bronchitis o It is a lymphoproliferative lung disorder characterized the presence of lymphoid follicles, coursing along the airways bronchi or bronchioles o It is rare in children. o Although the cause is unknown, an infectious aetiology has been proposed. o Onset of symptoms generally occurs by 6 weeks of age and peaks between 6 and 18 months. o Cough, moderate fever and fine crackles are common clinical findings. o Fine crackles generally, persist over time and recurrence of symptoms is common. o Chest radiographs may be relatively benign initially but evolve into the typical interstitial pattern. o Pulmonary function tests show restrictive pattern o Chest CT shows fine reticular pattern. Open lung biopsy is used to make definitive diagnosis. Pulmonary alveolar microlithiasis o This is a rare disorder. o Although the underlying cause of pulmonary alveolar microlithiasis is unknown, the disease is characterized by the formation of lamellar concretions of calcium phosphate or microlith, within the alveoli, creating a classic pattern on the radiograph. o Chest radiography typically reveal bilateral infiltrates with a fine sandlike micronodular appearance. o Although the mean age at the time of diagnosis is in the mid 30s the onset of the disease can occur during childhood. When symptomatic, individuals with pulmonary alveolar microlithiasis usually complain of dyspnoea on exeion and non productive cough. o Physical examinations of the lungs may reveal fine inspiratory crackles and diminished breath sounds. Clubbing occurs, although this is usually a more advanced sign. o Children are often asymptomatic on initial presentation. Diagnosis o Chest radiography typically reveals bL infiltrate with a fine sandlike micronodular appearance or Sandstorm appearance. o CT scan shows diffuse micronodular calcified densities. o Open lung biopsy reveals laminated calcific ioncretions within the alceoli. 