A rare cause of chronic cough and weakness

A 70-year-old patient, with a history of treated hypertension, a smoker, with gastritis and gastroesophageal reflux, came to the clinic because of a cough of 3 months with accompanying weakness, which did not allow him to perform daily tasks, sweating, drowsiness, upper limb tremor, anorexia and weight loss (~ 6 kg). The patient denies any other symptoms (fever, runny nose, headache, chest pain, nausea or vomiting) and explicitly states that his cough was sometimes mildly productive but he never developed haemoptysis. The patient states that he had prior visits to 3 different pulmonologists in the previous time period. Despite blood tests, chest CT scan (fibrous elements in the glottis) and spirometry, the cause of the cough was not found. Empirical administration of inhaled bronchodilators and corticosteroids did not improve the cough, while the other symptoms greatly worsened his quality of life.

During Examination the patient is thin, mildly depressed and the colour is good. He has good blood oxygenation and has no acrostic. The rest of the examination reveals mild tenderness in the epigastrium consistent with gastritis. The neurological examination confirms fine tremor of the upper limbs but without other neurological features. The cause of the symptomatology was not apparent on clinical examination, but the simultaneous occurrence of the symptoms was suggestive of a persistent infectious agent. In contrast, the absence of CT findings virtually ruled out the possibility of diseases with a severe prognosis such as cancer or tuberculosis (at least in the lungs).

A broad diagnostic screening for possible infectious and rheumatological causes was given but it was also considered appropriate to repeat gastroscopy and perform a visceral cranial CT scan to exclude the most common causes of chronic cough (asthma, sinusitis, gastro-oesophageal reflux disease). She was treated for gastritis and gastroesophageal reflux and given instructions until the tests were done.

The patient came back a month later with tests reporting that the symptoms persisted without any change. Testing was essentially negative, except for a marginally elevated value for a microbe called Coxiella burnetti. The antibody titer was low enough to justify the presence of infection, but it was considered appropriate to repeat the test at a reference centre, which confirmed the presence of the microbe with a high antibody titer. The patient was given doxycycline (100 mg x 2). One week later, and at subsequent visits, the patient reported significant improvement in his symptoms except for the tremor of the limbs. The patient completed 3 weeks of treatment and a neurological assessment for limb tremor (which was negative) was recommended. Improvement was rapid with complete resolution of symptoms.

Coxiella burnetti is a microbe that is endemic in various regions of Greece. Sheep, goats and cattle are the main intermediate host (the reservoir of the microbe). It is excreted in the milk, urine and faeces of infected animals, while high concentrations of the micro-organism are found in the amniotic fluid and placenta. Coxiella burnetii is highly resistant to heat, drought and several disinfectants. Humans are usually infected by inhaling contaminated air. Particles of the pathogenic microorganism may be suspended in the air along with dust from areas where the animal's body fluids are present. Transmission by ticks, consumption of unpasteurised milk or from person to person is rare.

Acute infection by the microbe is called Q fever (from query) and occurs after contact with infected animals or exposure to an infected environment. Symptoms of acute infection usually occur within 2-3 weeks of exposure (high fever, chills, headache, weakness, muscle pain, sweating, dry cough, nausea, diarrhoea, abdominal or chest pain). However, about 50% of people infected with the bacterium do not show the typical symptoms of infection.

Possible complications of Q fever are pneumonia, hepatitis, myocarditis and damage to the central nervous system. The estimated mortality rate due to Coxiella burnetii bacterial infection is quite low (<2% of hospitalized patients). However, when the infection is chronic it can be dangerous. Chronic infection occurs in less than 5% of people infected with Coxiella burnetii. Chronic Q fever may occur relatively soon (within 6 weeks) after acute infection or years afterwards. The most dangerous form of chronic infection is endocarditis which takes at least 18-24 months to treat.

Sources

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