A 1-year-old boy is admitted to the intensive care unit for severe respiratory distress and hypoxia requiring endotracheal intubation and mechanical ventilation. Medical history shows 2 prior episodes of pneumonia, chronic thrush, and tympanostomy tube placement for recurrent otitis media. His vaccinations are not fully up to date due to illness at the time of his well visits. The patient is at the 2nd percentile for height and weight. Physical examination shows diffuse crackles in both lungs. Laboratory results are as follows: Which of the following is the best long-term treatment for this patient?

Question

A 1-year-old boy is admitted to the intensive care unit for severe respiratory distress and hypoxia requiring endotracheal intubation and mechanical ventilation.  Medical history shows 2 prior episodes of pneumonia, chronic thrush, and tympanostomy tube placement for recurrent otitis media.  His vaccinations are not fully up to date due to illness at the time of his well visits.  The patient is at the 2nd percentile for height and weight.  Physical examination shows diffuse crackles in both lungs.  Laboratory results are as follows:  Which of the following is the best long-term treatment for this patient?

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11ec25c8_d62b_2030_bc81_6d4332c891bf_MD0003_00 This patient has recurrent and severe infections, failure to thrive, and lymphopenia (CD19+ = B cells, CD3+ = T cells). These findings are consistent with severe combined immunodeficiency (SCID). SCID is a severe primary immunodeficiency caused by one of several gene defects leading to failure of T cell development. Without cellular immunity, patients with SCID are at high risk for infections with viruses, fungi (eg, Candida [thrush]), and opportunistic pathogens (eg, Pneumocystis jirovecii). The loss of helper T cell function also causes B cell dysfunction (ie, impaired humoral immunity) and recurrent sinopulmonary bacterial infections (eg, pneumonia, otitis media). In addition to infection, failure to thrive and chronic diarrhea in infancy are typical. Stem cell transplantation is the only definitive therapy and should be performed as early as possible. Replacement of defective immature T cells with normal hematopoietic cells allows the development of a functional immune system. SCID is usually fatal in early childhood unless transplantation is performed. (Choice A) Antiretroviral therapy is used to treat patients with HIV infection. Perinatal HIV infection can present in a similar manner (eg, recurrent and severe infections, failure to thrive, lymphopenia) to SCID, but this patient's HIV test is negative. (Choices B and D) Intravenous immunoglobulin and broad-spectrum antibiotic therapy are short-term management options for SCID while awaiting transplantation. Intravenous immunoglobulin can be used for long-term therapy in certain humoral immunodeficiency syndromes (eg, X-linked agammaglobulinemia, common variable immunodeficiency). (Choice C) Live, attenuated vaccines (eg, measles-mumps-rubella, varicella) are contraindicated in SCID as they can cause severe or fatal disease. Inactivated vaccines are not contraindicated but will not result in protective immunity due to poor humoral response. Educational objective: Severe combined immunodeficiency presents in infancy with severe infections, failure to thrive, and chronic diarrhea. Absence of T cells and dysfunctional B cells are diagnostic. Treatment requires urgent stem cell transplantation. References: Transplantation of hematopoietic stem cells in human severe combined immunodeficiency: Long-term outcomes. (http://www.ncbi.nlm.nih.gov/pubmed/21116871)

A 1-Year-Old Boy Is Admitted to the Intensive Care Unit