Which clinical history findings are characteristic of severe combined immunodeficiency (SCID)?

Updated: Apr 28, 2021
  • Author: Robert A Schwartz, MD, MPH; Chief Editor: Harumi Jyonouchi, MD  more...
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Patients with severe combined immunodeficiency (SCID) may present with multiple severe or recurrent illnesses during the first months of life. Initially, growth appears normal, but failure to thrive with severe emaciation ensues secondary to diarrhea and chronic infections. In the past, SCID was often diagnosed after children acquired serious infections, such as pneumonia due to P jiroveci (carinii). Today, most infants should be recognized before the development of failure to thrive or Pneumocystis infection.

Within the first 3 months of life, infants with SCID present with persistent and recurrent diarrhea, otitis media, thrush, and respiratory infections (see the image below). In this setting, a thorough medical and family history, with particular attention to recurrent infections, should be obtained. The history should include questions about the following:

  • Family history of consanguinity

  • Sibling death in infancy (eg, multiple deaths during infancy due to infection or unexplained deaths in male infants) or previous miscarriages in the mother

  • Family history of SCID or other primary immunodeficiency

  • Poor feeding and poor weight gain

  • Chronic diarrhea

  • Previous infections, especially pneumonia

See the image below.

This patient presented with fever and paralysis of This patient presented with fever and paralysis of his left arm 3 months after receiving his third oral poliovirus vaccine. Past history included chronic thrush presenting in the absence of antibiotic therapy or breastfeeding at 2 months, chronic diarrhea from 4 months, and recurrent otitis media. He was at the 90th percentile for height and weight, similar to his parents. Major histocompatibility complex (MHC) class II deficiency was diagnosed by immunologic tests.

Diarrhea may be caused by rotavirus, adenovirus, and enterovirus. Cryptosporidiosis is also reported frequently. Diarrhea resembling Crohn disease complicates some types of SCID, such as major histocompatibility complex (MHC) class II deficiency.

Patients with SCID have repeated infections, which are typically more severe than comparable infections occurring in children with normal immunity. The frequency may be greater than 8 per year. Patients may require antibiotics for longer than 2 months; at times, intravenous (IV) antibiotics may be necessary. Patients with SCID may have recurrent deep skin or organ abscesses.

Mucocutaneous candidiasis is often more severe than expected and is resistant to treatment. Bacterial otitis media and pneumonia are common. Viral infections caused by varicella zoster virus (VZV), herpes simplex virus (HSV), respiratory syncytial virus (RSV), rotavirus, adenovirus, enterovirus, parainfluenza virus, Epstein-Barr virus (EBV), and cytomegalovirus (CMV) are seen. Asking the mother about risk factors for HIV infection is important; infants with transplacental HIV infection may present in much the same fashion as SCID.

Dismissing an infant’s death caused by an overwhelming common bacterial or viral infection without further investigation is a mistake. Whenever an infant with a history of unusually frequent and severe common infections dies of infection, an autopsy should be performed to assess lymphoid and thymic tissue. Peripheral blood lymphocytes can survive for several days; thus, blood should be saved for assessment of T-cell and B-cell markers by flow cytometry and for responses to mitogens.

Defects in the cell-mediated immune system become more apparent because breastfeeding may mask the humoral immune defects during the early neonatal period. T-cell defects, such as candidiasis affecting the esophagus, may occur. For example, cytomegalovirus (CMV) infection, measles, and varicella, which are usually self-limited, infect the lungs and the brain, resulting in life-threatening pneumonia, meningitis, and sepsis. Pulmonary involvement with P jiroveci (carinii) pneumonia (PCP) can also be severe.

Autoimmune phenomena, especially hemolytic anemia and neutropenia, are more common in CD3 deficiency and MHC class II mutations. The absolute lymphocyte count is less than 3000/μL, and the proliferative response of the lymphocytes to mitogens activation is less than 10% of control values.

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