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Ned is referred for an urgent chest X-ray ,
which reveals consolidation in the posterior basal segment of the left lower lobe , consistent with pneumonia .
Ned is prescribed amoxycillin 1g orally tds and doxycycline 100mg bd for community-acquired pneumonia , with suspicion of an atypical causative pathogen .
He is also referred for follow-up pathology , performed three days after the first blood test . The findings reveal improving neutrophilia ( 6.66 x 10 9 / L ). CRP has increased to 210mg / L . Ferritin is elevated at 483μg / L ( normal : 30-300 ), which is attributed to the inflammatory process . Biochemistry remains otherwise unremarkable . Respiratory viral PCR and Mycoplasma pneumoniae and Bordetella pertussis serology are negative .
Flavivirus IgG and IgM are reactive , and flavivirus IgM microsphere immunoassay ( MIA ) is equivocal . The flavivirus MIA includes dengue serotypes 1-4 , Japanese encephalitis , Murray Valley encephalitis , West Nile ( Kunjin ), Alfuy , Kokobera , Stratford , yellow fever and Zika viruses . This sample is later tested in parallel with the initially collected specimen , and no significant rise in IgG antibody level is demonstrated . It is thought that the flavivirus IgG relates to a previous infection and that the IgM is a cross-reaction .
Legionella pneumophila serology is negative , but L . longbeachae is positive at a titre of 512 , suggestive of recent L . longbeachae infection . Follow-up serology three weeks later shows an increased titre of 2048 .
Following the initial serological diagnosis , Ned is switched to oral azithromycin 500mg daily for seven days given that L . longbeachae has in-vitro resistance to doxycycline . His symptoms improve within three days .
Discussion
Legionnaire ’ s disease — pneumonia caused by legionella bacteria — was first recognised in 1976 following an outbreak of pneumonia at a hotel during an American Legion Convention . Legionella
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causes an atypical pneumonia . Initially , the term ‘ atypical ’ was used to indicate the non-classic clinical features , but today , it refers to pneumonia caused by L . pneumoniae , M . pneumoniae and Chlamydophila pneumoniae . These organisms cause of up to 60 % of community-acquired pneumonia cases and may be present along with bacteria that cause typical infection . 1-6
Legionella pneumonia can be serious and potentially fatal . The causative bacteria lives in natural water resources and has at least 60 different species . Two are commonly identified as causing disease in humans : L . pneumophila , which may contaminate cooling towers in large buildings and warm water systems ; and L . longbeachae , which may contaminate soil and potting mix . 1-6
Infection occurs when an individual inhales bacteria directly from the contaminated source . Human-to-human transmission does not occur . The incubation period is 2-10 days . Legionnaire ’ s disease is a notifiable disease , and if two or more cases are identified as being linked by time and place , then possible sources of infection are assessed . About 350-500 cases are notified in Australia annually . 1-6
Risk factors for infection include age over 50 ; smoking ; immunocompromise ; underlying lung , kidney or liver disease ; residence in care facilities ; recent admission to hospital ; or recent surgery . 1-6
Atypical pathogens cannot be reliably treated with beta-lactam antibiotics ( penicillin and cephalosporins ) and require tetracycline , macrolide or quinolone therapy . Azithromycin or ciprofloxacin are considered the drugs of choice for L . longbeachae as there is in-vitro evidence of resistance to tetracyclines . 7
Preventive strategies for legionella infection include regular treatment and cleaning and maintenance of water cooling and warm water systems . When handling potting mix or soil , it is advisable to wear gloves and a mask and to wash hands thoroughly after handling .
References on request from kate . kelso @ adg . com . au
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Legionella pneumonia can be serious and potentially fatal .
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What is the most likely diagnosis ?
a Pneumothorax b Diaphragmatic hernia c Diaphragmatic eventration d Subpulmonic pleural effusion
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ANSWER The answer is c . The chest X-ray reveals that the heart and left lung are displaced to the right and replaced by the stomach and large bowel loop . There are also multiple areas of atelectasis in the left lung . This is consistent with diaphragmatic eventration , which is confirmed on subsequent CT chest and abdomen .
Diaphragmatic eventration is rare , with limited literature support and few case reports worldwide . It describes abnormal elevation of a portion or entire hemidiaphragm due to a lack of muscle or nerve function . The diaphragm maintains its anatomical attachments . The abnormality can be congenital or acquired so can present in both paediatric and adult populations . The acquired type is more common . 1 , 2
The diaphragm is innervated by the phrenic nerve , which originates from the C3 , C4 and C5 spinal nerve roots . The left and right phrenic nerves provide motor function to each hemidiaphragm , respectively . Impaired development or injury to either nerve can lead to diaphragmatic paralysis or weakness . Depending on the severity of diaphragmatic involvement , patients may be asymptomatic or present with respiratory and / or gastrointestinal symptoms . Respiratory symptoms may include tachypnoea , central cyanosis if hypoxia is present ( rare in unilateral cases ), accessory muscle use , paradoxical movement of the chest wall during inspiration ( on the affected side ), decreased tactile fremitus and dullness to percussion on the affected side , and decreased breath sounds . Abdominal symptoms may include pain with palpation ( usually in the epigastric or periumbilical areas ), bowel sounds audible within the thoracic cavity and scaphoid abdomen ( in infants ).
Diagnosis is confirmed radiographically , and treatment is based on the aetiology and severity of the disease . Observant management may be appropriate in mild cases , but in severe disease ( such as requiring mechanical ventilation ) or in patients who are not adequately managed medically , surgical plication of the diaphragm may be indicated . 2
In this case , Kay is currently being managed conservatively , with corrective surgery scheduled in the near future .
References on request from kate . kelso @ adg . com . au
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