Adenosine deaminase deficiency severe combined immunodeficiency (ADA-SCID) is a type of severe combined immunodeficiency (SCID), which is a primary immunodeficiency that affects the immune system’s ability to fight and protect the body from infections. In SCID, the body’s immune cells (specifically T cells and including B cells and/or NK cells) are absent or not working properly, resulting in little or no immune response. This causes individuals with SCID to be highly susceptible to infections, and can be life-threatening if left untreated.

ADA-SCID is caused by a deficiency in the ADA enzyme, caused by a disease-causing genetic change (variant) in the ADA gene. When the ADA enzyme is not working properly, there is a build-up of purine metabolites, which can be toxic to developing immune cells (T, B and NK cells). This leads to depletion (reduction) of those immune cells and immune response. Symptoms and complications of ADA-SCID can vary, depending on the severity of the deficiency (how much ADA enzyme activity remains).

In Australia, SCID is often detected shortly after birth via newborn bloodspot screening (NBS) programs. For individuals who are not screened at birth, SCID is often diagnosed after symptoms develop. Early detection and diagnosis of SCID can ensure early interventions and prevent infections from being life-threatening to children with SCID.

Below on this page is some information about this condition as well as links to useful resources for Australians living with a rare disease.  

Synonyms: Severe combined immunodeficiency, autosomal recessive, t cell-negative, b cell-negative, nk cell-negative, due to adenosine deaminase deficiency; ada deficiency; adenosine deaminase-deficient severe combined immunodeficiency disease, scid, scid due to ada deficiency

Universal rare disease classifications provide a common language for recording, reporting and monitoring diseases. Please visit the Rare Disease Classifications page for more information about these internationally recognised classifications.

ORPHA:277 T-B-NK- severe combined immunodeficiency due to adenosine deaminase deficiency

ICD-11: 4A01.10 Severe combined immunodeficiencies

Rare diseases typically display a high level of symptom complexity. There is often a wide range of symptoms and the symptoms may vary between individuals in terms of its presentation, severity, duration and impact. 

Please speak to your medical team to learn more about the symptoms of this condition. 

Rare diseases are often serious and progressive, exhibiting a high degree of symptom complexity, leading to significant disability. Majority of the estimated two million Australians living with a rare disease meet the Australian Government’s definition for disability (in accordance to the Australian Public Service Commission and Australian Bureau of Statistics), and many experience severe and permanent disability impacts. If you or someone you care for is experiencing disability-related impacts from a rare condition, please speak with a health or disability professional for advice. Information about relevant disability support can be found at the RARE Portal’s Disability Support Information page.

ADA-SCID is a genetic condition. It is caused by a disease-causing genetic change (variant) in the ADA gene on Chromosome 20. This gene provides instruction to make an enzyme (type of protein) that helps recycle purines (the building blocks of DNA and RNA). When the ADA enzyme is not working properly, there is a build-up of purine metabolites, which can be toxic to developing immune cells (T, B and NK cells). 

All individuals have two copies (alleles) of the ADA gene – one on each chromosome that is inherited from each parent. ADA-SCID is an autosomal recessive condition, which means both copies of the ADA gene must have the disease-causing genetic variants for the condition to occur. ADA-SCID is the most common autosomal recessive form of severe combined immunodeficiency (SCID).

Individuals with the genetic variant in only one copy are unaffected but will be a carrier and may pass on that variant to their children. If both parents are carriers (each have a copy of the disease-causing variant), there is a 25% chance the child will inherit both disease-causing variants and have ADA-SCID  

More information on autosomal recessive inheritance pattern can be found at Centre for Genetics Education: Autosomal recessive inheritance. 

If you would like to learn more about the inheritance and impact of this condition, please ask your doctor for a referral to a genetic counsellor. Genetic counsellors are qualified allied health professionals who can provide information and support regarding genetic conditions and testing. More information about genetic counselling can be found at: 

• Information on Genetic Services 
• The National and State Services pages underneath the ‘Genetic Counselling’ sections listed 

A timely diagnosis is critical for better patient outcomes, the provision of the best possible care and treatment options, access to services and support, increased reproductive confidence and the ability to participate in clinical trials. 

Please speak to your medical team to learn more about the available diagnostic pathways for this condition. 

Please speak to your medical team to learn more about the possible treatment or management options for your condition. Treatment will depend on an individual’s specific condition and symptoms. It is also important to stay connected to your medical team so that you can be made aware of any upcoming clinical trial opportunities. For many rare diseases, treatment options may be limited. Participation in a clinical trial may provide access to new or emerging therapies.

Healthcare professionals involved in the care of individuals with RD may include general practitioners (GP), paediatricians, clinical geneticists, genetic counsellors, clinical immunologists, immunology nurses, haematologists, and others. The need for different healthcare professionals may change over a person’s lifetime and extend beyond those listed here. 

Clinical care for rare diseases often involves a multidisciplinary team of medical, care and support professionals. Please note that the information provided here is as a guide and that RVA does not necessarily monitor or endorse specific clinics or health experts.

This may not be applicable to all rare diseases but for many, palliative care services may be relevant and useful. Palliative care services are available for people (adults, children and their families) living with a life-limiting illness and is not only for end-of-life care. It can also help at any stage of illness from diagnosis onwards, and will look different for different people. Palliative care services provide assistance, support, resources and tools to help people manage their illness and the symptoms, ease pain, and improve comfort and quality of life. If this is relevant to you and you wish to find out more information about palliative care and how it can help you, please visit:

• Australian Institute of Health and Welfare: Palliative care Overview
• Australian Government Department of Health, Disability and Ageing: Palliative care
• Palliative Care Australia

If you know of any relevant care guidelines, please let us know via the Contribute page. 

Individuals living with rare diseases may have complex medical issues and disabilities, which are not always visible. It is often useful to refer to their medical history as well as personal information such as a medical card, doctor’s letter, or if available, a rare disease passport, for relevant information.

In addition, individuals, their parents, families and carers often develop extensive expertise on their specific rare disease. It is important to recognise that they can contribute valuable knowledge about their rare condition. Rare diseases often impact individuals differently, so it’s important to consider a person’s lived experience.

If you know of any relevant emergency management guidelines or information relevant to emergency care, please let us know via the Contribute page. 

Australian Organisation:

Immune Deficiencies Foundation Australia (IDFA)
Website: https://www.idfa.org.au/

IDFA is a national not-for-profit and leading peak body offering education, advocacy and awareness for Australians living with primary or secondary immunodeficiencies.

Please note that RVA does not monitor or endorse each group/organisation’s operational governance and activities. When engaging with a group, please consider the information on the RARE Portal’s Finding Helpful Peer and Community Supports page.

ADA-SCID varies between individuals, and each person’s experience is unique.

Immune Deficiencies Foundation Australia: SCID Newborn Screening page has personal stories of people living with ADA-SCID.

If you would like to share your personal story with RVA, please visit the Rare Voices Australia: Share Your Story page. RVA will consider your story for publishing on our website and inclusion on the RARE Portal.

For information on available government and social services that provide support for individuals with a rare disease, please visit the National and State Services pages.

People living with a rare disease often face unique challenges such as diagnostic delays, misdiagnoses, limited treatment options, and limited access to rare disease specialists and support. These challenges may impact people’s emotional wellbeing and quality of life. Many find it helpful to seek mental health and wellbeing support to cope with ongoing stress and uncertainty. Connecting with people who have shared experiences through a support group may also be helpful. Information about relevant mental health and wellbeing support can be found at:

• Mental Health and Wellbeing Support for Australians Living with a Rare Disease
• The National and State Services pages underneath the ‘Mental Health’ sections listed

Further information on ADA-SCID can be found at: 

• Genetic and Rare Diseases (GARD) Information Center: Severe combined immunodeficiency, autosomal recessive, t cell-negative, b cell-negative, nk cell-negative, due to adenosine deaminase deficiency 
• National Organization for Rare Disorders (NORD): severe combined immunodeficiency, autosomal recessive, T cell-negative, B cell-negative, NK cell-negative, due to adenosine deaminase deficiency
• Rare Awareness Rare Education Portal: Severe combined immunodeficiencies (SCID)

GeneReviews^®: Adenosine Deaminase Deficiency 

Online Mendelian Inheritance in Man, OMIM®: #102700; severe combined immunodeficiency, autosomal recessive, t cell-negative, b cell-negative, nk cell-negative, due to adenosine deaminase deficiency  

Orphanet: severe combined immunodeficiency, autosomal recessive, T cell-negative, B cell-negative, NK cell-negative, due to adenosine deaminase deficiency 

Human Phenotype Ontology (HPO): Severe combined immunodeficiency due to adenosine deaminase deficiency 

Australian Society for Clinical Immunology and Allergy: Immunodeficiency Strategy for Australia and New Zealand 

This page has been co-developed by Rare Voices Australia (RVA)’s RARE Portal team.

If you are aware of any additional information that may benefit stakeholders with an interest in this page, or if you notice any broken links or inaccurate information, please let us know via the Contribute page.