Severe combined immunodeficiency

A clinical syndrome with diverse genetic causes that results in profoundly impaired combined cellular and humoral immunity.

Early diagnosis is imperative as, without treatment, the condition is uniformly fatal in the first year of life.

Any child under the age of 1 year with an absolute lymphocyte count (ALC) of <3000/mm^3 should be investigated.

Haematopoietic stem cell transplantation, gene therapy, or enzyme replacement therapy (when applicable) are the definitive treatments.

Infants present with recurrent infections, failure to thrive, and chronic diarrhoea. Key findings on examination may include the absence of lymphoid tissue, poor weight gain, or diffuse erythematous rash.

Live vaccines should not be given to infants with suspected SCID.

Blood or blood products should be irradiated and test serologically negative for cytomegalovirus (CMV) infection before administration to patients with confirmed or suspected SCID.

Severe combined immunodeficiency (SCID) is a genetic syndrome characterised by a profound deficiency in cellular and humoral immunity and a markedly decreased number of T cells. Clinical manifestations begin early in life and include opportunistic infections, failure to thrive, and chronic diarrhoea.[1]Bonilla FA, Khan DA, Ballas ZK, et al. Practice parameter for the diagnosis and management of primary immunodeficiency. J Allergy Clin Immunol. 2015;136:1186-1205. http://www.jacionline.org/article/S0091-6749(15)00883-0/fulltext http://www.ncbi.nlm.nih.gov/pubmed/26371839?tool=bestpractice.com [2]Routes J, Abinun M, Al-Herz W, et al. ICON: The early diagnosis of congenital immunodeficiencies. J Clin Immunol. 2014;34:398-424. http://www.ncbi.nlm.nih.gov/pubmed/24619621?tool=bestpractice.com