Pneumonia is simply an infection of the lung tissue. It causes inflammation of the lung tissue and sputum filling the airways and alveoli. Pneumonia can be seen as consolidation on a chest xray.


If the pneumonia developed outside of hospital it is labeled labelled “community acquired pneumonia”. If it develops more than 48h after hospital admission it is labelled “hospital acquired pneumonia”. If it develops as a result of aspiration, meaning after inhaling foreign material such as food, then it is labelled “aspiration pneumonia”.



  • Shortness of breath
  • Cough productive of sputum
  • Fever
  • Haemoptysis (coughing up blood)
  • Pleuritic chest pain (sharp chest pain worse on inspiration)
  • Delirium (acute confusion associated with infection)
  • Sepsis



There may be a derangement in basic observations. These can indicate sepsis secondary to the pneumonia:

  • Tachypnoea (raised respiratory rate)
  • Tachycardia (raised heart rate)
  • Hypoxia (low oxygen)
  • Hypotension (shock)
  • Fever
  • Confusion


There are characteristic chest signs of pneumonia:

  • Bronchial breath sounds. These are harsh breath sounds equally loud on inspiration and expiration. These are caused by consolidation of the lung tissue around the airway.
  • Focal coarse crackles. These are air passing through sputum in the airways similar to using a straw to blow in to a drink.
  • Dullness to percussion due to lung tissue collapse and/or consolidation.


Severity Assessment

NICE recommend using the scoring system CRB-65 out of hospital and CURB-65 in hospital. The only difference is that out of hospital you do not count urea. When you see someone out of hospital with a CRB-65 score of anything other than 0 NICE suggest considering referring to the hospital.

  • CConfusion (new disorientation in person, place or time)
  • UUrea > 7
  • RRespiratory rate ≥ 30
  • BBlood pressure < 90 systolic or ≤ 60 diastolic.
  • 65 – Age ≥ 65


The CURB 65 score predicts mortality (score 1 = under 5%, score 3 = 15%, score 4/5 = over 25%). The scoring system is there to help guide whether to admit the patient to hospital:

  • Score 0/1: Consider treatment at home
  • Score ≥ 2: Consider hospital admission
  • Score ≥ 3: Consider intensive care assessment


Common causes

  • Streptococcus pneumoniae (50%)
  • Haemophilus influenzae (20%)


Other Causes and Associations

  • Moraxella catarrhalis in immunocompromised patients or those with chronic pulmonary disease
  • Pseudomonas aeruginosa in patients with cystic fibrosis or bronchiectasis
  • Staphylococcus aureus in patients with cystic fibrosis


Atypical Pneumonia

The definition of atypical pneumonia is pneumonia caused by an organism that cannot be cultured in the normal way or detected using a gram stain. They don’t respond to penicillins and can be treated with macrolides (e.g. clarithomycin), fluoroquinolones (e.g. levofloxacin) or tetracyclines (e.g. doxycycline).

Legionella pneumophila (Legionnaires’ disease). This is typically caused by infected water supplies or air conditioning units. It can cause hyponatraemia (low sodium) by causing an SIADH. The typical exam patient has recently had a cheap hotel holiday and presents with hyponatraemia.

Mycoplasma pneumoniae. This causes a milder pneumonia and can cause a rash called erythema multiforme characterised by varying sized “target lesions” formed by pink rings with pale centres. It can also cause neurological symptoms in young patient in the exams.

Chlamydophila pneumoniae. The presentation might be a school aged child with a mild to moderate chronic pneumonia and wheeze. Be cautious though as this presentation is very common without chlamydophilia pneumoniae infection.

Coxiella burnetii AKA “Q fever”. This is linked to exposure to animals and their bodily fluids. The MCQ patient is a farmer with a flu like illness.

Chlamydia psittaci. This is typically contracted from contact with infected birds. The MCQ patient is a from parrot owner.

TOM TIP: You can remember the 5 causes of atypical pneumonia with the mnemonic: “Legions of psittaci MCQs”

  • M – mycoplasma pneumoniae
  • C – chlamydydophila pneumoniae
  • Qs – Q fever (coxiella burnetii)


Fungal Pneumonia

Pneumocystis jiroveci (PCP) pneumonia occurs in patients that are immunocompromised. It is particularly important in patients with poorly controlled or new HIV with a low CD4 count. It usually presents subtly with a dry cough without sputum, shortness of breath on exertion and night sweats. Treatment is with co-trimoxazole (trimethoprim/sulfamethoxazole) known by the brand name “Septrin”. Patients with low CD4 counts are prescribed prophylactic oral co-trimoxazole to protect against PCP.



Patients in the community with CRB 0 or 1 pneumonia do not necessarily need investigations. NICE suggest considering a “point of care” test in primary care for CRP level to help guide management, however this is not widely available. If they arrive in hospital they will probably get a minimum of:

  • Chest xray
  • FBC (raised white cells)
  • U&Es (for urea)
  • CRP (raised in inflammation and infection)


Patients with moderate or severe cases should also have:

  • Sputum cultures
  • Blood cultures
  • Legionella and pneumococcal urinary antigens (send a urine sample for antigen testing)


Inflammatory markers such as white blood cells and CRP are roughly raised in proportion to the severity of the infection. The trend can be helpful in monitoring the progress of the patient towards recovery. For example, repeating WBC and CRP after 3 days of antibiotics may show a downward trend suggesting the antibiotics are working. CRP commonly shows a delayed response so may be low on first presentation then spike very high a day or two later despite the patient improving on treatment. WBC typically responds faster than CRP and give a more “up to date” picture.

Patients that are immunocompromised may not show an inflammatory response and may not have raised inflammatory markers.



Always follow your local area guidelines. These are developed by looking at the bacteria in the local area for their antibiotic resistance so are specific to that population. Moderate or severe pneumonia or septic patients usually start with IV antibiotics. These are then changed to oral antibiotics guided by clinical improvement or improvement in their inflammatory markers.

  • Mild CAP: 5 day course of oral antibiotics (amoxicillin or macrolide)
  • Moderate to severe CAP: 7-10 day course of dual antibiotics (amoxicillin and macrolide)



  • Sepsis
  • Pleural effusion
  • Empyema
  • Lung abscess
  • Death


Last updated February 2019
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