Croup is an infection of the larynx, trachea and sometimes its two branches, the principal bronchi. The technical name for it is laryngotracheitis or laryngotracheobronchitis, depending on what is affected. It is a disease of the upper airway and is distinct from bronchiolitis, which is a disease of the smaller airways.
While teenagers can get croup, it is principally a childhood disease, particularly affecting those between six months and three years of age. Boys tend to be affected slightly more than girls and it is more common during the winter months.
Viruses tend to be the main causative agent in croup, although bacteria such as mycoplasma may occasionally be implicated. Such viruses include para-influenza which accounts for the majority of cases, influenza, adenovirus, rhinovirus, echo virus, coxsackie, varicella-zoster, herpes simplex and respiratory syncytial virus (RSV). These viruses are also responsible for a number of other conditions including seasonal flu, the common cold, cold sores, chickenpox and bronchiolitis.
In addition to viral croup, there are a number of other conditions that may cause partial or even total upper airway obstruction. Epiglottitis has a high mortality risk and is often caused by a bacterium called haemophilus influenzae type B (HiB). The UK vaccination programme has largely eradicated HiB infections in children. Doctors will also want to rule out severe allergic reactions, throat abscesses and inhaled foreign bodies. Acid reflux may also masquerade as croup.
SYMPTOMS
As croup is an infection of the upper airway, it causes fever, sore throat, hoarseness, runny nose and a cough. The fever is usually but not always between 38 degs and 39 degsC, while the cough is very distinct and once heard, never forgotten. Medical textbooks often describe the cough as 'barking' or 'seal-like', and it is usually on the basis of the cough that the diagnosis is made.
COMPLICATIONS
In most cases, croup is a self-limiting illness that resolves over the course of a few days. Nevertheless, complications do occur, mainly due to upper airway swelling or lung disease. It can cause significant narrowing of the airway resulting in what is known medically as stridor which causes a harsh rasping sound on breathing in. Stridor in the context of croup occurs particularly at night time and can be very distressing.
Croup increases the risk of a bacterial infection in the upper airway, the middle ear known as otitis media or the lower respiratory tract usually referred to as pneumonia. An air leak in the lung known as a pneumothorax may also complicate croup. Without treatment, some of these complications may cause the child to stop breathing and ultimately death. In 2008, seven children died from croup in England and Wales.
TREATMENT
For the majority of children, croup does not require specific treatment and may be managed at home. Over-the-counter medication should be used to lower the child's temperature and to treat the sore throat. Aspirin should not be prescribed to children under the age of 16 due to the risk of Reye's syndrome - a very rare condition that causes serious liver and brain damage. The children should be encouraged to drink plenty of fluids to maintain adequate hydration.
While there is little medical evidence to support the use of steam or mist therapy in croup, often exposure to cool air significantly relieves symptoms, presumably due to reducing upper airway swelling - similar to putting an ice-pack on a bruise. With moderate disease, steroids are required to reduce upper airway swelling.
Less than 5 per cent of patients with croup will require hospital admission. Immediate medical advice should be sought if the child is distressed, suffering from significant breathing difficulties such as rapid breathing, the inability to inhale, feed or talk adequately, worsening cough or stridor, has blue lips, is drowsy or has a very fast or slow pulse.
Hospital treatment may include the use of oxygen, adrenaline nebulisers and steroids. Antibiotics are not routinely used unless the croup is complicated by a bacterial infection. Occasionally, a child may require a tube inserted into their airway to help them breathe.
Croup is usually self-limiting but it can be frightening for all concerned. Prevention by avoiding spreading germs is the best policy, but if you are concerned, you should always seek medical advice.
Dr Raj Thakkar BSc(Hons) MBBS MRCGP MRCP(UK) is a full-time GP in Buckinghamshire
