A 45-year-old man comes to the emergency department due to right-sided chest pain and cough. The patient describes the prodromal symptoms of malaise, nasal congestion, and runny nose that preceded the onset of cough 10 days ago. His cough has since worsened, and today, he developed sudden-onset, severe, right-sided chest pain after coughing. The patient has no shortness of breath or fever. He has no chronic medical conditions and takes no medications. The patient drinks 2 or 3 beers a day but does not use tobacco. Vital signs are normal. The patient is in acute distress due to pain. The nasal mucosa is boggy, and the posterior oropharynx is erythematous. The lungs are clear to auscultation, and heart sounds are normal. Marked tenderness is present on palpation over the right chest wall at the ninth rib area. Laboratory results are as follows:
| Complete blood count | |
| Hemoglobin | 13.5 g/dL |
| Platelets | 275,000/mm3 |
| Leukocytes | 15,200/mm3 |
| Segmented neutrophils | 13% |
| Bands | 1% |
| Eosinophils | 2% |
| Lymphocytes | 78% |
| Monocytes | 6% |
Which of the following is the most likely diagnosis in this patient?
Pertussis | |
Microbiology |
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Clinical |
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Diagnosis |
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Treatment |
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Prevention |
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This patient has a prolonged cough and sudden-onset, posttussive, focal rib pain consistent with a rib fracture. Along with lymphocytosis and absence of fever or abnormal lung findings, this presentation raises suspicion for infection with Bordetella pertussis, a highly contagious, gram-negative bacterium transmitted by respiratory droplets. Although unvaccinated children are at greatest risk, half of cases occur in adolescents/adults due to lack of immunization or waning immunity after vaccination.
B pertussis has tropism for the ciliated epithelium of the upper respiratory tract. Following attachment, the pathogen releases cytotoxins that denude respiratory epithelium, leading to a stepwise illness:
Catarrhal phase (weeks 1-2): Prodromal symptoms (eg, malaise, cough, rhinitis) are mild and nonspecific, as seen in this patient. Fever is absent or low-grade.
Paroxysmal phase (weeks 2-8): Damage to the ciliated epithelium causes microaspiration of oral secretions and results in coughing paroxysms. The classic inspiratory whoop and posttussive emesis are often absent in adults, but cough can be severe and result in rib fractures, hernia, or subconjunctival hemorrhage. Rib fractures, as in this patient, can result from sudden mechanical stress on the ribs due to vigorous coughing. Lung examination is typically unremarkable, and patients feel well between episodes. Lymphocyte-predominant leukocytosis (toxin-induced), as seen in this patient, is an important diagnostic clue.
Convalescent phase (weeks 8+): The cough gradually resolves over weeks to months.
(Choice A) Allergic bronchopulmonary aspergillosis causes prolonged cough but usually occurs in those with underlying asthma or cystic fibrosis. In addition, an elevated eosinophil, not lymphocyte, count is seen; coughing severe enough to cause rib fractures is not expected.
(Choice B) Aspiration pneumonia can cause prolonged cough, but fever and focal lung findings (eg, crackles) would be expected. Moreover, a neutrophil-predominant leukocytosis is typical.
(Choice C) Influenza causes nasal congestion and cough, but abrupt-onset fever and myalgia also usually occur. Moreover, symptoms gradually resolve, rather than worsen, after a week.
(Choice E) Tuberculosis often presents with prolonged cough, but fever is common and nasal symptoms are not. In addition, lung examination is typically abnormal (eg, decreased breath sounds, crackles), and paroxysmal cough causing rib fractures is not expected.
Educational objective:
Pertussis manifests as a stepwise illness beginning with 1-2 weeks of nonspecific symptoms and progressing to a paroxysmal cough; a normal lung examination and absence of fever are typical. Rib fractures can occur with vigorous coughing episodes, and lymphocyte-predominant leukocytosis is classic.