A 1-month-old boy is brought to the emergency department during winter with cough and difficulty breathing. He has had rhinorrhea, cough, and congestion for the past 3 days. Today, the patient began breathing harder and faster with increased cough. Temperature is 37.8 C (100 F) and respirations are 68/min. Oxygen saturation is 91%. The patient is alert and awake and has subcostal and suprasternal retractions. Mucous membranes are moist, and the anterior fontanelle is open and flat. Physical examination reveals diffuse expiratory wheezes and scattered rales. Which of the following pathogens is most likely causing this patient's condition?

Question

A 1-month-old boy is brought to the emergency department during winter with cough and difficulty breathing.  He has had rhinorrhea, cough, and congestion for the past 3 days.  Today, the patient began breathing harder and faster with increased cough.  Temperature is 37.8 C (100 F) and respirations are 68/min.  Oxygen saturation is 91%.  The patient is alert and awake and has subcostal and suprasternal retractions.  Mucous membranes are moist, and the anterior fontanelle is open and flat.  Physical examination reveals diffuse expiratory wheezes and scattered rales.  Which of the following pathogens is most likely causing this patient's condition?

Quizplus · Accepted Answer

11ec160b_3813_682d_9249_71551bb30ad2_MD0001_00 This infant with worsening cough and respiratory distress has diffuse wheezing and crackles, findings suggestive of bronchiolitis. Bronchiolitis is a lower respiratory tract infection that typically affects children age <2 years, usually during the fall and winter. The most common cause is respiratory syncytial virus (RSV). Initial symptoms include rhinorrhea and congestion, followed by cough, low-grade fever, and increased work of breathing. Classic findings include hypoxemia, tachypnea, and retractions with diffuse wheezes and crackles. Although illness severity typically peaks at 3-5 days, cough may last several weeks. In older infants and young children, bronchiolitis is typically a mild, self-limited illness. However, in premature or young (age <2 months) infants, symptoms may be severe (eg, cyanosis, poor perfusion, poor feeding) and lead to apnea and/or respiratory failure. Diagnosis of bronchiolitis is clinical, and treatment is supportive (eg, supplemental oxygen, nasal suctioning). (Choices A and D) Adenovirus most commonly causes pharyngitis with conjunctivitis and fever. Parainfluenza virus is the most common cause of croup (laryngotracheobronchitis), which presents with a barky, seal-like cough and inspiratory stridor. Both viruses cause bronchiolitis far less commonly than RSV does. (Choice B) Bordetella pertussis infection in infants classically causes upper respiratory symptoms (eg, rhinorrhea, congestion) with progression to a whooping cough and bouts of coughing and posttussive emesis. In contrast to this patient's examination, the lungs are usually clear to auscultation. (Choice C) Pneumonia caused by Mycoplasma pneumoniae typically presents with fever, cough, and rales and wheezing on examination. However, M pneumoniae usually affects children age >5 years and is a rare cause of bronchiolitis. (Choice F) Streptococcus pneumoniae is the most common cause of lobar pneumonia in children and presents with fever and cough. However, examination typically reveals focal rales, not diffuse findings, as seen in this patient. Educational objective: Viral bronchiolitis is most commonly caused by respiratory syncytial virus and presents with low-grade fever, cough, and respiratory distress (eg, tachypnea, retractions) in children age <2 years. Examination typically shows diffuse wheezes and/or crackles. __________ References: Pediatric bronchiolitis. (http://www.ncbi.nlm.nih.gov/pubmed/30137791)

A 1-Month-Old Boy Is Brought to the Emergency Department During