This baby's clinical picture--recurrent bacterial, viral, and fungal infections, failure to thrive, chronic diarrhea, and absent lymphoid tissue--are extremely concerning for severe combined immunodeficiency (SCID).
SCID is a primary immunodeficiency that can be caused by a number of genetic defects. The disease is transmitted in a X-linked fashion in approximately 50% of cases. The clinical picture of SCID is due to the absence of both B and T cells, leading to absent humoral and cell-mediated immunity. In addition to the signs discussed above, infants with SCID typically are athymic, as shown in Figure A. Both hematopoetic cell transplantation and, for certain forms of SCID, gene therapy, may be curative.
Reust discusses the evaluation of primary immunodeficiency disease in children. She notes that a family history of primary immunodeficiency is the strongest diagnostic predictor for this condition. She also notes that initial laboratory screening in patients with suspected primary immunodeficiency should include a complete blood count with differential, measurement of serum immunoglobulin, and measurement of complement levels.
Gaspar et al. present a case series of 10 children who underwent gene therapy with autologous hematopoetic cells transduced with a gammaretroviral vector. All patients were alive after a median follow-up period of 6.7 years, and had functional cell-mediated immunity with partial recovery of humoral immunity. One concerning complication was acute T cell ALL due to insertional mutagenesis.
Illustration A: Chest x-ray of an infant with SCID and no thymus.
Answer 1: SCID is invariably fatal without treatment.
Answer 3: This patient's infections are caused by an underlying immunodeficiency, so intravenous antibiotic therapy will not provide definitive treatment.
Answer 4: Immune globulin administration is indicated for less severe immunodeficiencies, such as common variable immunodeficiency.
Answer 5: Highly active antiretroviral therapy (HAART) is indicated for treatment of pediatric HIV; this patient's presentation is more consistent with SCID.
Reust CE. Evaluation of primary immunodeficiency disease in children. Am Fam Physician. 2013 Jun 1;87(11):773-8
PMID:23939499 (Link to Abstract)
Gaspar HB, Cooray S, Gilmour KC, Parsley KL, Adams S, Howe SJ, Al Ghonaium A, Bayford J, Brown L, Davies EG, Kinnon C, Thrasher AJ. Long-term persistence of a polyclonal T cell repertoire after gene therapy for X-linked severe combined immunodeficiency. Sci Transl Med. 2011 Aug 24;3(97):97ra79.
PMID:21865537 (Link to Abstract)