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Managing lysosomal storage disorders in the community

Sian Morgan
RGN
Specialist Nurse
Genzyme Homecare
E:sian.morgan@genzyme.com

Lysosomal storage disorders (LSDs) are a family of 40 genetic diseases, each of which typically affects fewer than 10,000 people worldwide. These diseases are all caused by a deficiency of one or more enzymes responsible for the breakdown of lipids or other molecules in cells of the body (see Figure 1). As these lipids accumulate, patients suffering from LSDs commonly experience developmental defects; damage to the brain, liver, lungs and other internal organs; defects in the neural and immune systems; skeletal abnormalities; and death at an early age.

[[NIP12_fig1_55]]

Many of these diseases, although rare, are progressive and degenerative, and may affect life expectancy. Their course can vary dramatically, becoming evident in infancy with early mortality in some individuals, to being relatively mild in others who may enjoy a normal lifespan.
At present there is no cure for these diseases although trials evaluating gene therapy are ongoing. Bone marrow transplantation can be of some benefit in a few of these diseases, such as mucopolysaccharidosis type I (MPS I). For three of the disorders, namely Fabry's, Gaucher's and MPS I, treatment is now available in the form of enzyme replacement therapy (ERT); therapy for several of the other disorders is in development.
This article will explore the use of ERT in the treatment of Fabry's and Gaucher's disease and, in particular, how this is now managed in the community.

Fabry's disease
In the case of Fabry's disease, the enzyme that is deficient is a-galactosidase A. Unlike most of these disorders, Fabry's disease is an X-linked recessive disorder, and symptoms can be identified in both males and females. The reported incidence varies from 1 in 40,000 (male patients) to 1 in 117,000 live births, reflected in numerous published articles. The average life expectancy for an adult untreated male is 40-45 years. Signs and symptoms of the disease usually manifest in childhood and continue to progress through adult life with increased morbidity (see Table 1). However, the symptoms and severity vary according to the individual.

[[NIP12_table1_56]]

[[NIP12_fig2_56]]
 
Gaucher's disease
Due to the deficiency of the enzyme glucocerebrosidase, there is a build-up of substrate in the lysosomes of macrophage cells turning these into so-called Gaucher's cells. These cells accumulate in specific tissues and organs of the body, causing dysfunction and damage (see Table 2). Gaucher's disease is a recessive disorder so an individual must inherit a defective gene from each parent to acquire the disease. There is a 1 in 4 chance of a pregnancy being affected, equal for males and females. It is a rare disease with around 10,000 people worldwide affected, and an increased incidence in the Ashkenazi Jewish population.

[[NIP12_table2_57]]
 
Diagnosis and treatment of LSDs
Although certain features of the disease may lead to a potential diagnosis, a definitive diagnosis is obtained by checking levels of enzyme in the blood in the case of Gaucher's disease, and also in the urine in the case of Fabry's. A DNA analysis can determine the specific genetic mutation, but although this will show the ­genotype, it will not necessarily give an indication as to the course or severity of the disease (phenotype).
Enzmye replacement therapy supplies the patient with the biologically deficient protein. ERT for Gaucher's disease was developed in the early 1990s and so some patients have been receiving therapy for over 10 years. In a paper about the effectiveness of ERT in Gaucher's disease, it states that: "[the] results indicate that among patients with type 1 Gaucher's disease, enzyme replacement therapy for as long as 5 years completely or partially ameliorates anaemia, thrombocytopenia, organomegaly, bone pain, and bone crisis."(1) ERT for Fabry's disease has been licensed since 2001.
Owing to the rarity of these diseases, a register can be used by each physician involved in the care of these patients to collect data to assist in gaining more knowledge about these disorders and thus enhance care. There are only a small number of centres in the country specialising within this area, requiring some individuals to take prolonged journeys to receive treatment. The aim of clinicians and others involved in the care of these patients has been to minimise the disruption to their lives by way of frequent hospital visits, particularly as they are potentially on this treatment for life.(2)

Role of the specialist homecare nurse
With the focus of healthcare in the treatment of chronic disorders moving from tertiary to primary care, nurses are at the forefront of providing services to meet patients' needs within the community setting. As a result a service has been set up to provide patient-centred care, with specialist nurses who are knowledgeable about these disease areas and who administer ERT at the patient's home.(3) The homecare nurse will meet the individual patient initially in the hospital setting, which is followed by a home visit. This is to ascertain whether the home circumstances are suitable, before the first home-based infusion, thus allowing the individual to be independent of the hospital environment. Where this is possible, a teaching pack is used to facilitate this process. The NHS Plan empowers patients to have more involvement in their care and assists them to take an active role in self-care.(4) The Department of Health's Expert patient report concludes that people who take a lead in managing their own chronic illness have improved health, as well as encouraging health professionals to promote this process.(5) If the person can receive ERT based at home, ongoing long-term support is provided according to the individual's needs. An individually-named nurse is assigned to each patient and a 24-hour helpline, direct to a specialist nurse, is also available throughout the year. The service aims to be as flexible as possible. A trained paediatric nurse is also available for children.(6) These specialist nurses may also assist in supporting hospital staff if home infusion is not possible, enabling the patient to attend a satellite unit within their local hospital. In this way the nurses are also able to promote and increase disease awareness by providing educational support to healthcare ­professionals. An additional ­service has been arranged for patients currently enrolled in clinical trials to receive their treatment at home. The nurse is able to adhere to the trial protocol and has regular contact with the principal investigator and centre. A patient wishing to travel can also receive their treatment away from home at their convenience, minimising ­disruption to their lives.
The role of the specialist nurse may be varied and challenging. Individuals diagnosed with an LSD will not only have the impact of diagnosis to deal with, but due to the hereditary nature of these diseases, may have other issues to come to terms with. A diagnosis may mean that other members of the family need or wish to be tested. Genetic counselling is available, and for those individuals wishing to start a family, prenatal testing may be considered. Specialist nurses are in a position to develop and maintain effective and appropriate communication networks. This is especially important when working within the community setting.
As treatments become available for the treatment of other LSDs, the role of the specialist nurse will widen to encompass caring for these patients within a variety of situations, thus ensuring excellent care to this group of patients.

References

  1. Weinreb N, Charrow J, Andersson H, et al. Effectiveness of ERT therapy in 1028 patients with type 1 gaucher disease after 2 to 5 years of treatment: A report from the Gaucher Registry. Am J Med 2002;113(2):112-9.
  2. Calley P. Paying to participate; ­financial, social and personal costs to parents of involvement in their ­children's care in hospital. J Adv Nurs 1997;25:746-52.
  3. Wilson J. What do patients want? Prof Nurse 2001;16(5):S7.
  4. Department of Health. The NHS Plan. London: Department of Health; 2000.
  5. Thomas S. Expert patient report. Primary Health Care 2001;11(9):20-1.
  6. Lewis M. The lifetime service: a model for children with life threatening illnesses and their families. Paediatr Nurs 1999;11(7):21-3.

Resources
The Society of Mucopoly-saccharide Diseases
T:01494 434156
W:www.mpssociety.co.uk

Gaucher Association
T:020 7433 1121
W:www.gaucher.org.uk

CLIMB (Children Living with Inherited Metabolic Disorders)
T:0800 652 3181
W:www.climb.org.uk