DiGeorge syndrome (DGS) is a primary immunodeficiency characterized by various degrees of T-cell deficiency. In partial DGS (pDGS), other risk factors could predispose to recurrent infections, autoimmunity, and allergy. The aim of this study was to assess the effect of different factors in the development of infections, autoimmunity, and/or allergy in patients with pDGS. We studied 467 pDGS patients in follow-up at Great Ormond Street Hospital. Using a multivariate approach, we observed that palatal anomalies represent a risk factor for the development of recurrent otitis media with effusion. Gastroesophageal reflux/dysphagia and asthma/rhinitis represent a risk factor for the development of recurrent upper respiratory tract infections. Allergy and autoimmunity were associated with persistently low immunoglobulin M levels and lymphopenia, respectively. Patients with autoimmunity showed lower levels of CD3+, CD3+CD4+, and naïve CD4+CD45RA+CD27+ T lymphocytes compared with pDGS patients without autoimmunity. We also observed that the physiological age-related decline of the T-cell number was slower in pDGS patients compared with age-matched controls. The age-related recovery of the T-cell number depended on a homeostatic peripheral proliferation of T cells, as suggested by an accelerated decline of the naïve T lymphocytes in pDGS as well as a more skewed T-cell repertoire in older pDGS patients. These evidences suggest that premature CD4+ T-cell aging and lymphopenia induced spontaneous peripheral T-cell proliferation might contribute to the pathogenesis of autoimmunity in patients with pDGS. Infections in these patients represent, in most of the cases, a complication of anatomical or gastroenterological anomalies rather than a feature of the underlying immunodeficiency.

The Wiskott Aldrich syndrome (WAS) is due to mutations of the WAS gene encoding for the cytoskeletal WAS protein (WASp), leading to abnormal downstream signaling from the T cell and B cell antigen receptors (TCR, BCR). We hypothesized that the impaired signaling through the TCR and BCR in WAS would subsequently lead to aberrations in the immune repertoire of WAS patients. Using next generation sequencing, the T cell receptor beta (TRB) and B cell immunoglobulin heavy chain (IGH) repertoires of 8 patients with WAS and 6 controls were sequenced. Clonal expansions were identified within memory CD4+ cells, as well as in total, naïve and memory CD8+ cells from WAS patients. In the B cell compartment, WAS patient IGH repertoires were also clonally expanded and showed skewed usage of IGHV and IGHJ genes, and increased usage of IGHG constant genes, compared with controls. To our knowledge, this is the first study that demonstrates significant abnormalities of the immune repertoire in WAS patients using next generation sequencing.

Autoimmune lymphoproliferative syndrome (ALPS) is a rare immunodeficiency caused by mutations in genes affecting the extrinsic apoptotic pathway (FAS, FASL, CASP10). This study evaluated the clinical manifestations, laboratory findings and molecular genetic results of 215 patients referred as possible ALPS. Double negative T-cell (DNT) percentage and in vitro apoptosis functional tests were evaluated by FACS; interleukin 10 and 18 (IL-10, -18) and soluble FAS ligand (sFASL) were measured by ELISA. Genetic analysis was performed by next generation sequencing. Clinical background data were collected from patients' records. Patients were categorised into definite, suspected and unlikely ALPS, and laboratory parameters were compared among these groups. From 215 patients, 38 met the criteria for definite ALPS and 17 for suspected ALPS. The definite and suspected ALPS patient population showed higher DNT than unlikely ALPS and had higher rates of lymphoproliferation. Definite ALPS patients had a significantly more abnormal in vitro apoptosis function with lower annexin than patients with suspected ALPS (P=0.002) and patients not meeting the ALPS criteria (P<0.001). The combination of elevated DNT and an abnormal in vitro apoptosis functional test was the most useful to identify all types of ALPS patients; the combination of abnormal in vitro apoptosis functional test and elevated sFASL was a predictive marker for ALPS-FAS group identification. Lymphoproliferation, apoptosis functional test and DNT are the most sensitive markers; elevated IL-10 and IL-18 are additional indicators for ALPS. The combination of elevated sFASL and an abnormal apoptosis function was the most valuable prognosticator for patients with FAS mutations.

Primary immunodeficiency diseases (PIDs) are genetically inherited diseases characterized by an increased susceptibility to infections, autoimmunity, lymphoproliferation, and malignancies. PIDs are under-diagnosed and the registered cases and reported prevalence are far below the estimated numbers especially in countries with large population and high consanguinity rates. Delays in diagnosis yield major morbidities and mortalities with resultant increased economic burden. Newborn screening using TRECs and KRECs, currently being implemented in some countries, is aimed through early diagnosis, to overcome the delays in the diagnosis and hence the poor outcome of some of the severe PIDs. However, the limited resources in developing countries challenges the implementation of newborn PID screening programs. There are considerable gaps in our knowledge that must be bridged. Setting the norms of TRECs and KRECs for each country is needed. Furthermore, some PIDs that might present in the neonatal period could not be detected by the current screening programs, and their diagnosis requires clinical expertise. Not to mention, local guidelines for the management of patients diagnosed by NBS should be set forth. Also, in the absence of NBS, clinicians should be aware of the early manifestations of PID. All these mandate conducting studies genuine to each country, developing programs for raising public awareness and clinical training of physicians to attain the required immunological skills.