GI Disorders in Patients With Primary Immunodeficiency
SCID is a heterogeneous group of congenital disorders characterized by molecular defects in both T- and B-cell function and are classified as T-B+NK+, T-B+NK-, T-B-NK+, or T-B-NK-. SCID is estimated to be in 1 of 50,000 to 500,000 live births. Infants with SCID present in the first year of life with severe recurrent bacterial or viral infections, eczematoid rashes, failure to thrive, and overwhelming sepsis. The genetic mutations that result in the SCID phenotype are deficiencies in adenosine deaminase, purine nucleoside, ZAP70, JAK3, and defects in the interleukin (IL)-7 receptor; the X-linked form, which is more common, results from a defect in the common gamma chain. The diagnosis of SCID is established when the absolute lymphocyte count is less than 2500 cells/mm, T cells make up less than 20% of the total lymphocytes, and the response to mitogens is less than 10% of the control. Serum levels of immunoglobulins are usually very low, and specific antibody responses are impaired. Diagnosis of infants often is delayed by several months as a result of the protection of maternal antibodies. When there is a prior SCID-affected child with a known specific molecular defect, a prenatal diagnosis can be made through genetic testing. Early recognition and diagnosis is crucial to these patients because bone marrow transplantation is necessary for survival. A newborn screening program is already in place in several states. Patients are often kept in isolation while awaiting the diagnosis and before treatment. Replacement Ig therapy is given, as well as prophylaxis for Pneumocystis jiroveci pneumonia. Live vaccinations should not be given to the patient or the patient's caregivers because they can cause life-threatening infections. Blood products are irradiated before administration to prevent graft-versus-host disease (GVHD).
Because SCID phenotypes involve both T- and B-cell dysfunction, GI disorders often occur in SCID patients. Oral, esophageal, and perianal candidiasis is common and can affect oral intake. Affected children develop severe diarrhea and malabsorption early in life, and stool should be sent to a laboratory to check for viral and opportunistic infections, especially rotavirus. Chronic infection with rotavirus has been reported in patients who have received the live vaccination. Cytomegalovirus and adenovirus infections also have been identified in GI biopsy specimens. GI biopsy specimens show hypocellular lamina propria, without plasma cells or lymphocytes. Villous atrophy may occur in some infants owing to damage in the intestine after viral or bacterial infections. Patients with SCID who receive blood transfusions or allogeneic bone marrow transplantation are susceptible to GVHD and a GVHD-like process affecting the colon and small intestine.
Combined T- and B-cell Immunodeficiency
Severe Combined Immunodeficiency
SCID is a heterogeneous group of congenital disorders characterized by molecular defects in both T- and B-cell function and are classified as T-B+NK+, T-B+NK-, T-B-NK+, or T-B-NK-. SCID is estimated to be in 1 of 50,000 to 500,000 live births. Infants with SCID present in the first year of life with severe recurrent bacterial or viral infections, eczematoid rashes, failure to thrive, and overwhelming sepsis. The genetic mutations that result in the SCID phenotype are deficiencies in adenosine deaminase, purine nucleoside, ZAP70, JAK3, and defects in the interleukin (IL)-7 receptor; the X-linked form, which is more common, results from a defect in the common gamma chain. The diagnosis of SCID is established when the absolute lymphocyte count is less than 2500 cells/mm, T cells make up less than 20% of the total lymphocytes, and the response to mitogens is less than 10% of the control. Serum levels of immunoglobulins are usually very low, and specific antibody responses are impaired. Diagnosis of infants often is delayed by several months as a result of the protection of maternal antibodies. When there is a prior SCID-affected child with a known specific molecular defect, a prenatal diagnosis can be made through genetic testing. Early recognition and diagnosis is crucial to these patients because bone marrow transplantation is necessary for survival. A newborn screening program is already in place in several states. Patients are often kept in isolation while awaiting the diagnosis and before treatment. Replacement Ig therapy is given, as well as prophylaxis for Pneumocystis jiroveci pneumonia. Live vaccinations should not be given to the patient or the patient's caregivers because they can cause life-threatening infections. Blood products are irradiated before administration to prevent graft-versus-host disease (GVHD).
Because SCID phenotypes involve both T- and B-cell dysfunction, GI disorders often occur in SCID patients. Oral, esophageal, and perianal candidiasis is common and can affect oral intake. Affected children develop severe diarrhea and malabsorption early in life, and stool should be sent to a laboratory to check for viral and opportunistic infections, especially rotavirus. Chronic infection with rotavirus has been reported in patients who have received the live vaccination. Cytomegalovirus and adenovirus infections also have been identified in GI biopsy specimens. GI biopsy specimens show hypocellular lamina propria, without plasma cells or lymphocytes. Villous atrophy may occur in some infants owing to damage in the intestine after viral or bacterial infections. Patients with SCID who receive blood transfusions or allogeneic bone marrow transplantation are susceptible to GVHD and a GVHD-like process affecting the colon and small intestine.
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