Paediatric medicine - Cystic fibrosis

Families benefit from an interested, supportive primary care team working with the local specialist cystic fibrosis centre, writes Dr Noreen West.

Heelp prick testing can show possible indicators of CF in newborns
Heelp prick testing can show possible indicators of CF in newborns

Cystic fibrosis (CF) is the most common life-limiting genetic condition in the UK.

With improving treatment, life expectancy continues to improve and is predicted to increase into the 40s for children born with CF in 2009. Despite this, there are only about 8,000 people living with CF in the UK, meaning the average GP surgery will only provide care for one CF patient, and will rarely be involved in the diagnosis of a new CF patient.

Following the national introduction of newborn screening in 2008, increasing numbers of suspected CF cases and CF carrier states are being identified, making a basic knowledge of CF more relevant.

What is CF?
CF is an autosomal recessive condition caused by a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. There are more than 1,600 known genetic mutations for CF, with the delta F508 mutation accounting for more than 70 per cent of mutations in the UK population.

CFTR codes for the CFTR protein, which is a cyclic-AMP regulated chloride channel in the epithelial cell membrane. Consequently, there is reduced secretion of chloride and subsequent movement of water from inside to outside the cell, resulting in thickened mucus and a reduction in the epithelial surface liquid.

CFTR is expressed throughout the body, resulting in a multi-system disease, particularly affecting the respiratory and digestive tracts.

Newborn screening
On their initial blood spot screening, 0.5 per cent of babies will have an immunoreactive trypsin above the cut-off point, although only a small proportion (4/10,000) will subsequently be identified to have CF. Having a newborn identified as a carrier for CF or requiring further heel prick testing is often a source of great anxiety for parents.

When a baby is identified as having CF through screening, the specialist CF centre will be notified and should liaise immediately with the GP and health visitor to identify any health concerns. A joint home visit to discuss the result with the family is recommended. Carrier status is notified directly to the GP and any concerns about the infant should prompt a referral to the local CF specialist centre.

Respiratory symptoms
Respiratory involvement is present in almost all CF patients and is the most common cause of eventual death.

There may be a persistent or recurrent 'wet sounding' or productive cough, although children rarely expectorate sputum. Wheezing, which does not respond to or is poorly controlled with asthma treatment, is also present.

Other respiratory features include recurrent pneumonia, breathlessness on exercise, focal and recurrent crepitations. The child may have digital clubbing and signs of chest deformity such as bowing of the sternum.

Patients with mild variant disease may not develop respiratory symptoms until adulthood.

Gastrointestinal symptoms
About 10 per cent of infants with CF present at birth with meconium ileus causing intestinal obstruction, usually prior to hospital discharge. Failure to pass meconium within 48 hours of birth, with signs of obstruction, needs prompt surgical review.

The baby may pass frequent, offensive stools that look poorly formed, greasy and pale or have abdominal distension and discomfort, or even rectal prolapse. It is often useful to see a nappy as first-time parents may not appreciate abnormal stools.

Faltering or sub-optimal growth despite adequate intake is another sign. It is very common for babies with CF to feed excessively but still demonstrate poor weight gain.

About 10 per cent of children with CF produce sufficient pancreatic enzymes and do not have signs of malabsorption.

Other presentations
Other presentations include chronic sinusitis and acute pancreatitis, particularly in CF patients who are pancreatic sufficient. Nasal polyps are uncommon in children and have a high association with CF.

In male infertility, 1-2 per cent is secondary to congenital absence of the vas deferens, which is associated with one or two CF mutations in 90 per cent of cases.

Around 1-3 per cent of echogenic bowel cases on antenatal scans are associated with CF.

Making a referral
Many of the above symptoms have more than one potential cause. Referral to a general paediatrician or a paediatrician with a respiratory or gastrointestinal interest is appropriate.

If you have a patient with an identified CF mutation who develops any of the symptoms above, a discussion/referral direct to your local CF centre for further investigation would be appropriate.

Diagnostic investigations such as a sweat test (sweat has a high chloride level in CF) and CF mutation genotyping should only be initiated by a paediatrician after appropriate discussion with the child/family.

Expert patients
Patients and families with CF rapidly become 'expert patients' with knowledge on the management of common CF problems such as mild respiratory exacerbations and will often seek advice directly from the CF centre, bypassing primary care.

The relationship with primary care remains important and there are two distinct ways that the service is used: as 'lay' patients, consulting for non-CF-related problems and as 'expert' patients, seeking practical help for CF-related problems.1

Parents may struggle emotionally following diagnosis and the GP and health visitor's support is often well received.

Common CF consultations
A 'new' cough should always be treated, even if the child looks well and has no signs in their chest. A broad spectrum antibiotic such as co-amoxiclav will cover the common CF pathogens (Staphylococcus aureus, Haemophilus influenzae and Moraxella catarrhalis). Ideally, a respiratory specimen should be sent prior to starting treatment. Your local CF centre is likely to have guidelines for their preferred antibiotic and dosage.

Support for home intravenous therapy is more likely to be necessary in adult patients but re-siting cannulas, serum antibiotic levels and so on can have a positive impact on a sick patient at home.

Prescription problems are the most common complaints CF centres hear about primary care. Many families find it very burdensome to make frequent trips for repeat prescriptions and prescription reviews, while inadequate drug provision, particularly for essential items such as enzyme replacement therapy (many young people need several tubs a week), can be a problem.

Summary
Although CF is a rare and complex disease, the numbers of patients living into adulthood will continue to increase. Many families benefit from an interested, supportive primary care team who are sensitive to their requirements. Most CF centres would love to engage more actively with a patient's GP and would be receptive to enquiries to help management partnerships to develop.

  • Dr West is consultant paediatrician in cystic fibrosis, Sheffield Children's Hospital

References

1. Lawton et al. Adult cystic fibrosis patients' experiences of primary care consultations: a qualitative study. Br J Gen Pract 2006; 56(528): 518-25.

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