Discussion
PIDs are rare inherited diseases involved the immune system, typically associating with recurrent and severe infection, autoimmune disease and increased incidences of malignancies. At present, fast diagnosis of PID in non-specialized hospitals or clinics across China accompanies with great challenges. Delayed diagnosis and misdiagnosis commonly occur, mainly leading to poor clinical prognosis. In the current research, we studied 112 patients with PID during 6 years in our hospital based on their clinical, immunological, and molecular characteristics, aiming to provide a reference for perfect diagnosis of PID.
In the present research study, the most common PID was combined immunodeficiencies (28.6%), followed by HIGM syndrome (24.1%), predominantly antibody-deficiency diseases (17.8%), combined immunodeficiencies with associated or syndromic features (12.5%), congenital defects of phagocyte number or function (10.7%), diseases of immune dysregulation (3.6%), defects in intrinsic and innate immunity (1.8%), and complement deficiencies accounted for about 0.9% of cases, which were found to be different from those previously reported [
6‐
8] probably because our hospital is a tertiary referral center and our cases were in-patients and a number of them were admitted from elsewhere. Therefore, the proportion of patients with PID, who are prone to have severe complications and difficult to diagnose, significantly increased. In addition, our hospital is one of the main referral centers for allo-HSCT in China, and some of the PID patients in our study were previously diagnosed with PID in other hospitals who needed to receive allo-HSCT. Furthermore, we cannot ignore a possibility that a number of differences were based on race and relative incidence of disease in our population. Our data further showed that the male/female ratio was 6.0:1, and 60.7% of the cases presented symptoms less than 6 months. Besides, 17.8% of the patients in our study had family history of PID, which was found similar to a previous study [
8].
Repeated and chronic infections, particularly pulmonary infections, are a main feature of PID. Large sample cohort studies on PID indicated that almost all patients with PID had a history of recurrent infection before diagnosis was finalized [
9‐
11]. In agreement with those reports, the present study revealed that 97.3% of PID patients presented recurrent infections before diagnosis. The most common occurrences were respiratory tract infection, followed by bacterial infection of the skin and mucous membranes in 38 cases (33.9%). Of note, gastrointestinal disorders are frequent in patients with PID [
12,
13]. Moreover, 26 (112, 23.2%) patients with infectious or noninfectious diarrhea showed a poor growth as well. Besides, PID-related gastrointestinal diseases not only are caused by infection, but also by autoimmunity, an inflammatory response, or malignancy. Recurrent gastrointestinal symptom could be the first presentation of PID, thus physicians should be aware of the possibility of PID in patient with intractable diarrhea, malabsorption, and failure to thrive, especially those cases who failed to respond to conventional treatment strategies [
14,
15].
Sarmiento et al. reported 7.65% of AEFI in patients with PID [
16]. The majority of cases of AEFI have occurred in patients with CGD, SCID, and idiopathic primary hypogammaglobulinemia. It was reported that BCG is a vaccine, mainly associating with AEFI in patients with PID [
17]. In the current study, AEFI was found in 20.5% of patients with PID after vaccination, especially with BCG vaccine, and included extra regional lymph nodes, skin, or lungs as the most common clinical presentations. For patients with CGD and SCID, the percentage of BCG-osis was 100 and 28.1%, respectively, which found to be in line with previously reported findings [
18‐
20]. Notably, 17.8% of the cases included family history of PID. Because BCG vaccination is routinely carried out at birth in China, PID patients who receive BCG vaccination before immune deficiency are highly suspected. BCG vaccination should be avoided if any family history or clinical or laboratory evidence concerns a neonate’s immune competency. Moreover, disseminated BCG infection should be suspected in any vaccinated infants who accompany with a persistent fever or comparable disease of unknown etiology.
In addition to recurrent and severe infections, immunity disorder is commonly observed in PID patients, especially in patients who accompany with predominantly antibody deficiencies [
21,
22]. A recent study, that involved an Iranian cohort of 471 patients, reported inflammatory manifestations in 26.5% of patients. Furthermore, the prevalence of immunity disorder appeared to increase with age in PID cohorts, influencing a significant proportion of patients [
23]. In this study, we also found that not only autoimmune gastrointestinal disease, but also autoimmune cytopenias were the common autoimmune manifestations in patients with PID. When a child associates with autoimmune manifestations, the possibility of incidence of PID should be highly taken into account.
Immunoglobulin replacement therapy and allo-HSCT are effective therapeutic strategies for patients with PID. On the basis of previous reports, immunoglobulin replacement therapy was found to be effective for 83% of children with hypogammaglobulinemia [
24,
25]. At present, the majority of patients with PID only receive symptomatic treatment. Allo-HSCT, which has been used as an effective treatment for PID [
26,
27], isn’t frequent in China. The 2-year OS rate in the SCID patients was 90% during 25 months of follow-up [
28]. A total of 47 cases underwent allo-HSCT and the OS rate was 78.7% (37/47) in the present study, which was in agreement with those findings previously reported [
27]. However, the OS widely differed among PID patients with different phenotypes who underwent allo-HSCT. The 2-year OS rate for SCID, HIGM syndrome, and the remaining of PID patients who underwent allo-HSCT was 14.3, 83.3, and 100%, respectively. The OS of SCID is mainly poor because SCID patients are often severely infected, and bone marrow transplantation of severely infected SCID children has a poor prognosis. Compared with patients with active infection and older age who underwent allo-HSCT, OS was better in those patients who received a transplant when they were younger and free from infection. Thus, allo-HSCT is more effective in younger PID children, and allo-HSCT is often helpful when an appropriate donor is available.
However, the present study contains some limitations, including its retrospective nature, small sample size, and all the cases were recruited at a single center. A possible selection bias also might be present because the clinical data were taken from hospitalized children with PID. Further researches involving more PID patients and multiple centers are required in the future study.
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