1. Introduction Post-infectious bronchiolitis obliterans (PIBO) is due to an inflammatory response in the lower respiratory tract that results in malfunction of the distal airways from a severe respiratory viral infection. Most often PIBO is a non- progressive disease, seldom requiring lung transplant when treated with all supportive care measures. In this case a Caucasian male with RSV, adenovirus and rhinovirus developed respiratory failure requiring intubation and high ventilator pressures resulting in bronchiolitis obliterans. Subsequently, he developed failure to thrive, respiratory insufficiency and is being considered for lung transplant. Progressive post-infectious bronchiolitis obliterans in a toddler Christopher Hovland, PGY-2, MD, Alma Chavez, MD McLane Children’s Hospital at Baylor Scott & White Healthcare and Texas A&M Health Science Center College of Medicine, Temple, TX Case Presentation (cont) At subsequent outpatient follow-up it was noted that patient continued to have tachypnea and retractions with occasional use of home oxygen during exacerbations. He continued to also have poor exercise capacity and poor weight gain. Given the potential need for lung transplant, he was referred for infant pulmonary function testing to obtain objective analysis of his pulmonary status and prognosis. Case Presentation A 23 month old Caucasian term male with a medical history of wheezing presented to the emergency department with cough, congestion, fever, increased work of breathing and cyanosis with spO2 of 20%. Immediate stabilization included sedation, intubation, mechanical ventilation and treatment with bronchodilators. An initial VBG showed a respiratory acidosis with pH of 7.16, CO2 of 79, and HCO3 of 28. In the PICU, physical exam was remarkable for mottled skin, bilateral rhonchi, scattered expiratory wheezes, capillary refill time of 3 seconds, hypercapnia, ecchymosis of left eyelid, and abrasion to left cheek. Initially there was a concern for non- accidental trauma but after evaluation with imaging, lab work and forensics this was determined to not likely be the cause of patient’s insult. Upon further review with the family it was noted that patient had a history of coughing and wheezing episodes triggered when the patient gets a URI. He had been on nebulizer treatments with bronchodialators as needed for this at home. He had not had any history of recurrent ear infections, atopy, food allergies, thrush or difficulty with stools. There are multiple family members that were noted to have asthma. One sibling also had history of multiple hospitalizations for apnea and bradycardia. Patient was not exposed to any environmental tobacco smoke or pet dander. Only otherwise noted to have a history of speech delay and clumsiness with secondary bruising. While in the PICU he continued on mechanical ventilation, IV fluids, sedation, anesthesia, continuous albuterol nebs for 2 weeks and required high peak inspiratory pressure and low PEEP to maintain acceptable ventilation. A partial sepsis work-up was negative, and a respiratory viral panel serially performed returned positive for first RSV (day 2), then RSV & adenovirus (day 9), then rhinovirus (day 23). The patient also initially had elevated liver transaminases of AST-379 and ALT- 250. Subsequently on day six of hospitalization it was noted that patient had developed hepatomegaly. An ultrasound was obtained confirming the hepatomegaly, but liver transaminases had trended down by day 10 and the hepatomegaly improved. This was thought likely due to viral infection. On hospital day 21 pediatric pulmonology recommendations included inhaled corticosteroids, a trial of systemic steroids, influenza vaccine, and follow-up as outpatient. An immune work-up was suggested by infectious disease and was unremarkable. The systemic steroids did not improve his status and at time of discharge (day 36) was noted to have persistent tachypnea, retractions, decreased exercise capacity, and muscle weakness. The patient failed to keep a pulmonology follow-up appointment and approximately three months after initial hospitalization was readmitted for severe respiratory distress due to influenza A. He was initially evaluated by PCP in clinic and was noted to be in respiratory distress and hypoxic. He had hypoxia treated with high-flow nasal cannula. At this time his mother reported a 2 day history of cough/congestion without fever. Chest radiograph at admission (Fig 1) was noted to have hyperexpanded lungs with accentuated perihilar opacities compatible with viral pneumonitis/reactive airway disease. He was admitted and stabilized and upon chart review it was noted he had lost 0.5 kg since his last PCP visit the month prior. He was noted to have failure to thrive (weight & length < 3 rd percentile and weight/length at 3 rd percentile). Pediatric pulmonology was again consulted and a recommended high resolution CT of the chest was consistent with bronchiolitis obliterans (Fig 2). These findings included diffuse mild tubular bronchiectasis in both lungs, groundglass mosaic pattern related to air trapping. It was also suggested he continue home medications of bronchodialators and inhaled corticosteroids; as well as obtain a CF panel, that was unremarkable. Patient was started on azithromycin for anti- inflammatory effects, twice daily hypertonic saline nebs with airway clearance via vest/CPT, and nutritional enhancement. Patient was discharged home after extensive education and arrangement for appropriate supportive care and close follow- up. Discussion Post-infectious bronchiolitis obliterans (PIBO) is due to an inflammatory response in the lower respiratory tract that results in malfunction of the distal airways from a severe respiratory viral infection. Risk factors for development of PIBO include: adenoviral infection, mechanical ventilation, prolonged hospitalization, and hypercapnea. 1 It is unclear if mechanical ventilation can be linked as a direct cause or if it is simply a consequence of the initial infection. 1 The gold standard for diagnosis is accomplished by obtaining a lung biopsy but due to underlying respiratory issues most patients are never biopsied. 2 Currently a clinical picture of PIBO can be used in conjunction with CT findings (Table 1) to diagnose PIBO. High-resolution CT has significantly aided with diagnosis and the common findings seen on CT are shown in Table 2. When performed pulmonary function tests often show a fixed obstructive pattern with a decrease in FEV1 to less than 30%. 1 Once diagnosed, treatment is mostly supportive with a multi-disciplinary approach. The most common supportive measures include oxygen when needed, chest physiotherapy to aide in airway clearance, adequate nutrition, immunization against influenza/pneumonia, and avoidance of exposure to tobacco smoke. 1 Other forms of treatment including bronchodilators, steroids (systemic/inhaled), and antibiotics are varied in response in PIBO patients. 1 Most often PIBO is a non-progressive disease, seldom requiring lung transplant when treated with all supportive care measures. However, those patients who are younger and/or have bilateral disease have greater odds of increased morbidity due to mainly persistent symptoms and poor nutrition. 1 Some studies have shown as high as a 17% mortality rate from PIBO. 1 Since there is currently no cure for bronchiolitis obliterans, early recognition of severe respiratory illness and initiation of supportive care by implementing a multi-disciplinary treatment approach is extremely important and could potentially reduce hospital stay, improve care coordination, and decrease morbidity. References 1.da Silva Champs N, Lasmar L, Camargos P, Marguet C,Bueno Fischer G, Teresinha Mocelin, H. Post- infectious bronchiolitis obliterans in children. J Pediatr (Rio J). 2011;87(3):187-198. 2.Fischer GB, Sarria EE, Mattiello R, Mocelin HT, Castro-Rodriguez JA. Post infectious bronchiolitis obliterans in children. Paediatr Respir Rev. 2010;11:233-9. Texas Pediatric Society Electronic Poster Contest FIG 1. Chest radiograph at time of 2 nd admission TABLE 1. Diagnostic criteria for PIBO. 2 TABLE 2. CT changes seen in children & adolescents in patients diagnosed with PIBO. 2 FIG 2. Axial image of high resolution chest CT scan. Note ground glass mosaic pattern.