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IgA deficiency samer kareem 3,139 Views • 2 years ago

Selective immunoglobulin A deficiency (SIgAD) is a primary immunodeficiency disease and is the most common of the primary antibody deficiencies.[1] Total immunoglobulin A deficiency (IgAD) is defined as an undetectable serum immunoglobulin A (IgA) level at a value < 5 mg/dL (0.05 g/L) in humans. Partial IgAD refers to detectable but decreased IgA levels that are more than 2 standard deviations below normal age-adjusted means.[2, 3] IgAD is commonly associated with normal B lymphocytes in peripheral blood, normal CD4+ and CD8+ T cells, and, usually, normal neutrophil and lymphocyte counts. Anti-IgA autoantibodies of the IgG and/or IgE isotype may be present. Peripheral blood may also be affected by autoimmune cytopenias, eg, autoimmune thrombocytopenia,[4, 5] and patients may have other autoimmune phenomena. IgA was first identified by Graber and Williams in 1952; ten years later, the first patients with IgAD were described. IgAD is a heterogeneous disorder, and the results of intensive study are beginning to elucidate genetic loci and molecular pathogenesis that contribute to various subtypes of this disorder. Several lines of evidence suggest that, in many cases, IgAD and common variable immunodeficiency (CVID) have a common pathogenesis, which is discussed further in Pathophysiology. Other data indicate different genetic risk factors. Family studies show variable inheritance patterns. Familial inheritance of IgAD occurs in approximately 20% of cases,[6] and, within families, IgAD and CVID are associated.[7, 8] Many IgAD patients are asymptomatic (ie, "normal" blood donors) and are identified by finding a laboratory abnormality, without any apparent associated clinical disease. Some patients with IgAD may have the following associated conditions: (1) deficits in one or more immunoglobulin G (IgG) subclasses (this accounts for 20-30% of IgA-deficient patients, many of whom may have total IgG levels within the normal range) or (2) a deficient antibody response to pneumococcal immunization (specific polysaccharide antibody deficiency [SPAD]). Some patients with IgAD later develop CVID, and family members of patients with CVID may have only selective IgAD. Characterization of the receptor for the transmembrane activator and calcium-modulator and cyclophilin ligand interactor (TACI), encoded by the gene TNFRSF13B ( tumor necrosis factor receptor superfamily member 13B), suggests that people with the C104, A181E, and ins204A variants may be at risk for IgAD that progresses to CVID.[9] Primary IgAD is permanent, and below-normal levels have been noted to remain static and persist after 20 years of observation.[10] A recent report documents a rare case of reversion.[11] Environmental factors such as drugs or infections can cause IgAD, but this form is reversible in more than half the cases (see Causes). Although individuals with IgAD have largely been considered healthy, recent studies indicate a higher rate of symptoms. A 20-year follow-up study that compared 204 healthy blood donors with incidentally identified IgAD to 237 healthy subjects with normal IgA levels demonstrated that 80% of IgAD donors and 50% of control subjects had episodes of infections, drug allergy, or autoimmune or atopic disease. Severe respiratory tract infections occurred in 26% of IgAD subjects, in 24% of subjects with decreased IgA levels, and in 8% of control subjects; however, the incidence of life-threatening infections was not increased. IgAD is more common in adult patients with chronic lung disease than in healthy age-matched control subjects.[12] Patients with IgAD are at some increased risk of developing severe reactions after receiving blood products.[13, 14, 15] IgG anti-IgA antibodies may cause severe transfusion reactions if patients with IgAD are given whole blood; therefore, IgA-poor blood or washed red cells are preferred for those patients. IgA-deficient patients with immunoglobulin E (IgE)–class anti-IgA antibodies are at risk for anaphylaxis if they receive blood or intravenous immunoglobulin, but this situation is extremely rare. Individuals with such an unusual profile should receive only low IgA intravenous immunoglobulin preparations. However, caution must be used when administering IGIV to patients with IgAD if their anti-IgA status is unknown. A history devoid of previous blood product administration does not exclude the possibility of anti-IgA antibodies or adverse reactions. Fortunately, appropriate precautions can significantly reduce morbidity (see Treatment). Blood banks can use a simple ELISA screening approach to establish an IgAD blood donor poo

Severe combined immunodeficiency samer kareem 1,677 Views • 2 years ago

Severe combined immunodeficiency (SCID) is a life-threatening syndrome of recurrent infections, diarrhea, dermatitis, and failure to thrive. It is the prototype of the primary immunodeficiency diseases and is caused by numerous molecular defects that lead to severe compromise in the number and function of T cells, B cells, and occasionally natural killer (NK) cells. Clinically, most patients present before age 3 months. Without intervention, SCID usually results in severe infection and death in children by age 2 years. A committee of experts, initially sponsored by the World Health Organization (WHO), meets every 2 years with the goal to classify the group of primary immunodeficiency diseases according to current understanding of the pathways that become defective in the immune system.[1] Eight classification groups have been determined, with SCID being one of the best studied. Over the past few decades, the diverse molecular genetic causes of SCID have been identified with progress from studies of the immune system.[2] SCID is considered a pediatric emergency because survival depends on expeditious stem cell reconstitution, usually by bone marrow transplantation (BMT). Appropriate diagnosis is essential because instituting proper treatment is lifesaving. Despite the heterogeneity in the pathogenesis of immune defects, common cutaneous manifestations and typical infections can provide clinical clues in diagnosing this pediatric emergency.[3] Skin manifestations were prevalent in primary immunodeficiency disorders studied in 128 pediatric patients in Kuwait; skin infections were the most prevalent findings, seen in 39 patients (30%), followed by dermatitis in 24 (19%).[4] Skin infections were significantly more prevalent in those with congenital defects in phagocyte number, function, or both, as well as in those with well-defined immunodeficiencies. Dermatitis was evident in all patients with hyper–immunoglobulin (Ig) E syndrome and Wiskott-Aldrich syndrome.[4] Erythroderma of infancy with diffuse alopecia was seen exclusively in patients with SCID disorders, and telangiectasia in patients with ataxia telangiectasia; and partial albinism with silvery gray hair was associated with Chediak-Higashi syndrome. With the advances in BMT and gene therapy, patients now have a better likelihood of developing a functional immune system in a previously lethal genetic disease. However, once an infant develops serious infections, intervention is rarely successful.

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