Case Study: Diagnosing pneumonia mimics


Pneumonia has been recognized by the medical profession since ancient times. It is one of the leading causes of infectious deaths in the West and cause of considerable mortality and morbidity in our part of the world. Diagnosis is mostly based on history, clinical findings, and X-rays. Exact proof of infection and the ability to isolate the organism from blood and sputum culture is only available in less than half of the cases we see. Empirical treatment is begun on patients after sending the necessary microbiology samples, depending upon the regional antibiotic sensitivity or antibiotic policy.


A 34-year-old male came in with a high-grade fever. He initially had a cough, but that had subsided. He was admitted to another hospital for one week and received antibiotics. He experienced no shortness of breath or chest pain. Upon examination, though he was febrile, he was in good general condition, and his vitals were stable. Examination of his respiratory system showed normal breath sounds and resonant percussion notes on left chest, but right lower chest had decreased breath sounds and was dull in percussion resonance. Other systems were normal. His chest X-ray is shown below.

pneumonia mimic 1 - kasim

Blood routine, urea, and creatinine levels were normal. Sputum culture did not grow anything. The patient was screened for dengue, leptospira and malaria.

We performed a chest ultrasound; the report showed no significant fluid, mostly consolidation. The patient was put on another set of antibiotics and continued to be febrile for the next four days. Finally, we decided to do a chest CT scan.[s2If !is_user_logged_in()]…

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pneumonia mimic 3 - kasim pneumonia mimic 2 - kasim

The report showed eventration of the diaphragm, with the liver under the dome of the diaphragm. We stopped his antibiotics, and he became afebrile the next day and was discharged. We explained to him about the shadow in the X-ray and instructed him to always keep his X-ray with him when he goes to any doctor in the future. He came back for a review after two weeks and had no complaints. The probable explanation is that he had a viral fever, which later turned into an antibiotic fever, immediately disappearing upon stopping the antibiotics.


Nearly all doctors encounter pneumonia in their daily practice. Most cases of community-acquired pneumonia are treated by general practitioners and general medicine doctors. Pulmonologists are usually involved only in difficult cases. Failure to respond to the initial course of antibiotics is the main stimulus to investigate a patient for non-infectious causes of chest X-ray shadows. There may be some clues in the patient’s medical history and clinical examination. In elderly people, we have to look and listen carefully for any possibility of primary or secondary malignancy or complication of their treatment. In young people, the search for collagen vascular diseases and non-infectious granulomas comes first.

Table 1. Non-infectious mimics of pneumonia
Pulmonary neoplasms

  • Endobronchial lesions with or without obstruction
  • Bronchoalveolar cell carcinoma
  • Lymphoma, Kaposi sarcoma

Radiation pneumonitis
Collagen vascular diseases

  • Systemic lupus erythematosus
  • Polymyositis, Dermatomyositis
  • Mixed connective tissue diseases

Pulmonary embolism
Granulomatous diseases

  • Wegeners, Churg-Strauss
  • Sarcoidosis

Drug-induced pulmonary diseases
Hypersensitivity pneumonitis
Undocumented X-ray shadow and unrelated fever

  • Eventration of diaphragm
  • Foreign bodies
  • Breast calcification or implants


Review the history and available evidence again. Chase results of cultures sent at admission. A repeated chest X-ray is required to confirm non-resolving pneumonia. A CT chest scan will give further insight into anatomical and diagnostic possibilities. CT pulmonary angiograms are possible with the newest generation of CT machines, so talk to the radiologist before sending the patient. A bronchoscopy with biopsy and washing is mandatory in most cases. If no diagnosis comes out with above work-up, such patients will need a direct lung biopsy, surgically or with a thoracoscope. Discuss with the pathologist about the possibilities in your mind to facilitate correct reporting of the samples.


Treatment is based on the diagnosis and possible etiology. Empirical antibiotics should be stopped if there is no benefit and the patient is not toxic.

Key Point

X-ray shadows that are not actually pneumonia can be mistaken for pneumonia when accompanied by fever. A clinician should be vigilant about pneumonia-mimics when the lesion is not responding to the initial treatment.

About The Author

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Dr. Kasim Kolakkadan, MBBS, MD Pulmonology, MRCP(UK), is currently a Consultant Pulmonologist at the Alshifa Hospital, Perinthalmanna, Kerala, India and an assistant professor of pulmanology at KMCT Medical College.


References (click to show/hide)

  1. Nonresolving pneumonia and mimics of pneumonia. Medical Clinics of North America – Volume 85, Issue 6 (November 2001).
  2. Rajagopala S. Singh N. Nada R. Gupta D. An unusual cause of nonresolving pneumonia. Respiratory Care. 54(9):1266-9, 2009 Sep.
  3. Ferretti GR. Jankowski A. Rodiere M. Brichon PY. Brambilla C. Lantuejoul S. CT-guided biopsy of nonresolving focal air space consolidation. Journal of Thoracic Imaging. 23(1):7-12, 2008 Feb.
  4. Gross, T J. Chavis, A D. Lynch, J P 3rd. Noninfectious pulmonary diseases masquerading as community-acquired pneumonia. Clinics in Chest Medicine. 12(2):363-93, 1991 Jun.
  5. Shen HC. Wu TT. Lin SH. Medical image. A case of nonresolving pneumonia. Cryptogenic organising pneumonia. New Zealand Medical Journal. 123(1320):91-3, 2010 Aug 13.
  6. Cabreros, L J. Rajendran, R. Drimoussis, A. Brandstetter, R D. Radiographic mimics of pneumonia. Pulmonary disorders to consider in differential diagnosis. New Rochelle Hospital Medical Center, New York, USA. Postgraduate Medicine. 99(1):139-42, 145-6, 1996 Jan.


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  1. ravikumar bhaskaran
    Posted Jan 2014 at 2:22 pm | Permalink

    Yes, it can be only drug fever. But the problem faced by a general physician like me is that the relatives as well as the patient will harp on the symptom of FEVER even if I tell them that it is better to have fever and not to reduce it by fourth hourly paracetamol. The practical difficulty is that even in our Medical College Trivandrum paracetamol is given on a fourth hourly basis. So the pattern of the fever cannot be ascertained.
    my mail

  2. surya prakash
    Posted Jan 2015 at 3:42 pm | Permalink

    I suggest that CBC may be very helpful in diagnosing bacteria pneumonia,leucocytosis is common in bacterial pneumonia while it is normal or leucopenia in viral cases. Simple GBP is very informative.

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