Combined B-Cell and T-Cell Deficiencies

COMBINED B-CELL AND T-CELL DEFICIENCIES

Pathophysiology

Combined B-cell and T-cell deficiencies are those disorders of the immune system that have elements of dysfunction of both the B cells and T cells. A variety of inherited (autosomal recessive and X-linked) conditions fit this description. These conditions have in common disruption of the normal communication system of B cells and T cells and impairment of the immune response (Porth, 2002). These conditions generally appear early in life. Ex-amples of these deficiencies are discussed below.

Ataxia-telangiectasia is an autosomal recessive disorder af-fecting both T- and B-cell immunity. In 40% of patients with this disease, a selective IgA deficiency exists. IgA and IgG subclass deficiencies, along with IgE deficiencies, have been identified. Variable degrees of T-cell deficiencies are observed and become more severe with advancing age. The disease is associated with neurologic, vascular, endocrine, hepatic, and cutaneous abnor-malities. It is accompanied by progressive cerebellar ataxia, telangi-ectasias, recurrent bacterial infection of the sinuses and lungs, and an increased incidence of cancer (Buckley, 2000).

Both B and T cells are missing in severe combined immuno-deficiency disease (SCID). SCID is a phenotypic term that isused for a wide variety of congenital and hereditary immunologic defects that are characterized by early onset of infections, defects in both B- and T-cell systems, lymphoid aplasia, and thymic dys-plasia. Inheritance of this disorder can be X-linked, autosomal-recessive, or sporadic. The exact incidence of SCID is unknown; it is recognized as a rare disease in most population groups, with an incidence of about 1 case in 1,000,000. This illness occurs in all racial groups and both genders (Parslow et al., 2001). Wiskott-Aldrich syndrome is a variation of SCID compoundedby thrombocytopenia (loss of platelets). The prognosis is gener-ally poor because most affected infants develop overwhelming fatal infections.

Clinical Manifestations

The onset of ataxia (uncoordinated muscle movement) telangi-ectasia (vascular lesions caused by dilated blood vessels) usually oc-curs in the first 4 years of life of those with ataxia-telangiectasia. Many patients, however, remain symptom-free for 10 years or longer. As patients approach the second decade of life, chronic lung disease, mental retardation, neurologic symptoms, and physical disability become severe. Long-term survivors develop progressive deterioration of immunologic and neurologic func-tions. Some affected patients have reached the fifth decade of life. The primary causes of death in these patients are overwhelming infection and lymphoreticular or epithelial cancer.

The onset of symptoms occurs within the first 3 months of life in the majority of patients with SCID with respiratory infections, pneumonia (often secondary to P. carinii), thrush, diarrhea, and failure to thrive. Many of these infections are resistant to treat-ment. Shedding of viruses such as respiratory syncytial virus or cytomegalovirus from the respiratory and gastrointestinal tracts is persistent. Maculopapular and erythematous skin rashes may occur. Vomiting, fever, and a persistent diaper rash are also com-mon manifestations (Parslow et al., 2001).

Medical Management

Treatment of ataxia-telangiectasia includes early management of infections with antimicrobial therapy, management of chronic lung disease with postural drainage and physical therapy, and management of other presenting symptoms. Other treatments in-clude transplantation of fetal thymus tissue and IVIG adminis-tration (Chart 51-2).

Treatment options for SCID include stem cell and bone marrow transplantation. The ideal donor is an HLA-identical sibling (Parslow et al., 2001). Other treatment regimens include IVIG replacement, administration of thymus-derived factors, and thymus gland transplantation. Gene therapy has been used, but the results have thus far been disappointing. As treatment im-proves, an increased number of those who previously would have died in infancy may live to adulthood.

Nursing Management

As many patients require immunosuppression to ensure engraft-ment of depleted bone marrow during certain transplantation procedures, nursing care must be exquisite, with attention to pre-venting the transmission of infection to patients. Use of standard precautions and meticulous hand hygiene is essential in caring for these patients. Reverse isolation procedures, where nurses pro-tect the patient by donning gowns, gloves, caps, and so on, is essential. The patient’s condition must be monitored at all times as a certain number of patients experience reactions to transplan-tation that can be fatal.