Chapter 219: B and T Cell Immunodeficiencies—Severe Combined Immunodeficiency (SCID) and Other Well Defined Primary Immunodeficiencies

Patient Story

A 2.5-month-old-baby boy presented to his pediatrician because of a 10-day history of diarrhea, which began soon after his first series of immunizations, which included the oral rotavirus vaccine. He was born via uncomplicated vaginal delivery and his birth weight and height were at the 55 percent percentile. There were no known ill contacts. His weight and height, which had been 15 percent at two months, was now lower and he had a fever to 101F. Thrush was noted on his tongue and throat, and he was noted to have a diffuse scaling rash on the face and hands (Figures 219-1 and 219-2). A CBC with differential showed an absolute lymphocyte count of 1,200 cells/microliter. A chest x-ray was performed which showed diffuse infiltrates and the absence of a thymic shadow. He was referred to an immunologist for immediate evaluation and treatment. T and B cell subsets were obtained, which revealed that 90 percent of his lymphocytes are B cells and that he had very low numbers of T of maternal origin and NK cells. He was treated with intravenous immune globulin (IVIG), placed on trimethoprim-sulfamethoxazole for Pneumocystis jirovecii prophylaxis and referred to a specialized immunology center for a bone marrow transplant. His bone marrow transplantation was successful.

Introduction

Combined immunodeficiency syndromes arise from genetic defects leading to T lymphocyte dysfunction. Because B cells require T cells to produce antibodies, these patients are susceptible to opportunistic infections as well as skin and sinopulmonary infections due to bacterial, viral and fungal organisms. Immune dysregulation can lead to autoimmune disease and auto-inflammation in some syndromes. A diagnosis of a Severe Combined Immunodeficiency (SCID) is fatal before the age of 2 years if untreated and is a medical emergency. Some well-defined primary immunodeficiencies including Wiskott-Aldrich Syndrome, Hyper IgE syndrome, and Ataxia Telangiectasia may present in older patients.

Synonyms

• Primary or Congenital Immunodeficiency.

• Swiss type agammaglobulinemia.

• T-Cell Deficiency.

• Bubble Boy Disease.

Epidemiology

• SCID is very rare with an incidence reported at 1.8/100,000 live births per year.¹

• Newborn screening with T cell receptor excision circles (Trec) has found a rate of 1.64/100,000 tests in Wisconsin. Trec screening does miss some atypical forms of SCID.²

• The etiologies of these defects are variable ...