Severe combined immunodeficiency

Last reviewed: 22 Feb 2023
Last updated: 09 Nov 2022



History and exam

Key diagnostic factors

  • at-risk demographic
  • family history of SCID, infant death, or consanguinity
  • recurrent and unusually severe infections
  • chronic diarrhea
  • failure to thrive
  • absent lymphoid tissue
More key diagnostic factors

Other diagnostic factors

  • rash
  • oral or genital ulcers
  • microcephaly
  • skeletal abnormalities
  • blindness
  • dystonia
  • radiation sensitivity
Other diagnostic factors

Risk factors

  • Family history of SCID
  • Family history of infant death
  • Athabascan-speaking Native American people
  • Consanguinity
More risk factors

Diagnostic investigations

1st investigations to order

  • CBC
  • flow cytometry
  • chest x-ray
  • quantitative immunoglobulin test (IgG, IgM, and IgA)
More 1st investigations to order

Investigations to consider

  • chest ultrasound
  • CT scan of the chest
  • MRI chest
  • fundoscopy
  • enzyme testing
  • serum uric acid
  • T-cell proliferation studies
  • polymerase chain reaction-based viremia testing
  • radiation sensitivity of fibroblast cultures
  • genetic testing
More investigations to consider

Treatment algorithm


confirmed SCID



Javier Chinen, MD, PhD


Pediatrics, Allergy, and Immunology

Baylor College of Medicine

Texas Children’s Hospital




JC declares that he has no competing interests.


Dr Chinen would like to gratefully acknowledge Dr John M. Cunningham, Dr James L. LaBelle, Dr John Routes, Dr James Verbsky, Dr Nicole Chase, and Dr Ebrahim Shakir, the previous contributors to this topic.


JLL, JR, JV, and NC are authors of references cited in this topic. JMC and ES declare that they have no competing interests.

Peer reviewers

Elizabeth Secord, MD

Professor of Pediatrics

Division of Immunology

Wayne State University School of Medicine




ES declares that she has no competing interests.

Waseem Qasim, BMedSci (Hons), MBBS, MRCP (UK), MRCPCH, PhD

Senior Lecturer

Institute of Child Health

Consultant in Paediatric Immunology & Bone Marrow Transplantation

Great Ormond Street Hospital




WQ declares that he has no competing interests.

  • Severe combined immunodeficiency images
  • Differentials

    • 22q11.2 Microdeletion Syndrome/DiGeorge syndrome
    • Omenn syndrome
    • Zeta chain-associated protein 70 deficiency
    More Differentials
  • Guidelines

    • Recommendations for screening and management of late effects in patients with severe combined immunodeficiency after allogeneic hematopoietic cell transplantation
    • Practice parameter for the diagnosis and management of primary immunodeficiency
    More Guidelines
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