Human PLCG2 haploinsufficiency results in a novel natural killer cell immunodeficiency

BACKGROUND

Although most individuals effectively control herpesvirus infections, some suffer from severe and/or recurrent infections. A subset of these patients possess defects in natural killer (NK) cells, lymphocytes that recognize and lyse herpesvirus-infected cells; however, the genetic etiology is rarely diagnosed. PLCG2 encodes a signaling protein in NK-cell and B-cell signaling. Dominant-negative or gain-of-function variants in PLCG2 cause cold urticaria, antibody deficiency, and autoinflammation. However, loss-of-function variants and haploinsufficiency have not been reported to date.

OBJECTIVES

The investigators aimed to identify the genetic cause of NK-cell immunodeficiency in 2 families and herein describe the functional consequences of 2 novel loss-of-function variants in PLCG2.

METHODS

The investigators employed whole-exome sequencing in conjunction with mass cytometry, microscopy, functional assays, and a mouse model of PLCG2 haploinsufficiency to investigate 2 families with NK-cell immunodeficiency.

RESULTS

The investigators identified novel heterozygous variants in PLCG2 in 2 families with severe and/or recurrent herpesvirus infections. In vitro studies demonstrated that these variants were loss of function due to haploinsufficiency with impaired NK-cell calcium flux and cytotoxicity. In contrast to previous PLCG2 variants, B-cell function remained intact. Plcg2+/- mice also displayed impaired NK-cell function with preserved B-cell function, phenocopying human disease.

CONCLUSIONS

PLCG2 haploinsufficiency represents a distinct syndrome from previous variants characterized by NK-cell immunodeficiency with herpesvirus susceptibility, expanding the spectrum of PLCG2-related disease.

Sensitization to Common Allergens Among Children with Asthma and Allergic Rhinitis in Qatar

Background

Childhood asthma (A) and allergic rhinitis (AR) are common in Qatar. Aeroallergens sensitization is integral in disease pathogenesis and clinical presentation. Determining sensitization patterns assists clinicians in tailoring an efficient medical management.

Objective

To determine the aeroallergen sensitization pattern and relationship to clinical parameters.

Methods

A retrospective review of children (2-14-years) files with i) Pediatric Allergist/or Pulmonologist confirmed-diagnosis of A, and AR, and ii) positive skin prick test (SPT).

Results

Among 473 patients (69.1% males; 30.9% females), aged 7.6 years, family history was positive in 66.3%: 59.4% in A, 64.2% AR, and 78.2% A-AR. The number of allergens/patients was 2.1±1.7. Median eosinophil count was 400 cells/ul and IgE 287 KU/L. Rates of A, AR, and A-AR varied significantly in children ≤5 years compared to >10 years: A was 43.2% vs 17.8%, and AR 34.5% vs 16.4%. Two hundred and four children (43.1%) were mono-sensitized, 215 (45.5%) oligosensitized (2-3 allergens), and 54 (11.4%) polysensitized (≥4 allergens). A-AR ranked the top number of positive allergens. The commonest aeroallergen was Der p1 (38.1%), followed by Der f (29.0%), cat (22.6%), alternaria (18.8%), American cockroach (18.4%), and dog (14.0%). House dust mite (HDM) and American cockroach were commoner in ≤5 years than older >10-year children (52.5%, 24.1%), while cat and dog allergens were commoner in older ones (37.1%, 21.6%).

Conclusion

Family history is quite positive in patients with A and AR. Common aeroallergens include HDM, cats, and alternaria in the young children, while animal allergens were commoner in the older children.

A founder RAB27A variant causes Griscelli syndrome type 2 with phenotypic heterogeneity in Qatari families

Griscelli syndrome type 2 (GS2) is a rare autosomal recessive disorder caused by pathogenic variants in the RAB27A gene and characterized by partial albinism, immunodeficiency, and occasional hematological and neurological involvement. We reviewed and analyzed the medical records of 12 individuals with GS2 from six families belonging to a highly consanguineous Qatari tribe and with a recurrent pathogenic variant in the RAB27A gene (NM_004580.4: c.244C > T, p.Arg82Cys). Detailed demographic, clinical, and molecular data were collected. Cutaneous manifestations were the most common presentation (42%), followed by neurological abnormalities (33%) and immunodeficiency (25%). The most severe manifestation was HLH (33%). Among the 12 patients, three patients (25%) underwent HSCT, and four (33%) died. The cause of death in all four patients was deemed HLH, providing evidence for this complication's fatal nature. Interestingly, two affected patients (16%) were asymptomatic. This report highlights the broad spectrum of clinical presentations of GS2 associated with a founder variant in the RAB27A gene (c.244C > T, p.Arg82Cys). Early suspicion of GS2 among Qatari patients with cutaneous manifestations, neurological findings, immunodeficiency, and HLH would shorten the diagnostic odyssey, guide early and appropriate treatment, and prevent fatal outcomes.

Biallelic mutations in DNA ligase 1 underlie a spectrum of immune deficiencies

We report the molecular, cellular, and clinical features of 5 patients from 3 kindreds with biallelic mutations in the autosomal LIG1 gene encoding DNA ligase 1. The patients exhibited hypogammaglobulinemia, lymphopenia, increased proportions of circulating γδT cells, and erythrocyte macrocytosis. Clinical severity ranged from a mild antibody deficiency to a combined immunodeficiency requiring hematopoietic stem cell transplantation. Using engineered LIG1-deficient cell lines, we demonstrated chemical and radiation defects associated with the mutant alleles, which variably impaired the DNA repair pathway. We further showed that these LIG1 mutant alleles are amorphic or hypomorphic, and exhibited variably decreased enzymatic activities, which lead to premature release of unligated adenylated DNA. The variability of the LIG1 genotypes in the patients was consistent with that of their immunological and clinical phenotypes. These data suggest that different forms of autosomal recessive, partial DNA ligase 1 deficiency underlie an immunodeficiency of variable severity.

Camel's milk allergy

INTRODUCTION

Camel's milk is a safe and therapeutic nutrient. Camel's milk allergy is almost unknown.

OBJECTIVE

To identify the clinical and laboratory features of camel's milk allergy.

METHODS

In this retrospective study, the records of patients with camel's milk allergy were reviewed. Data collected included age, sex, clinical presentation, concomitant allergies, family history, laboratory tests (complete blood cell count [CBC], white blood cell [WBC] count, total immunoglobulin E [IgE], food specific IgE), and skin-prick tests (SPT) to camel's milk and other foods.

RESULTS

Nine patients (four male patients, five female patients; mean age ± SD 4.3 ± 2.4 years) presented with cutaneous urticaria and/or angioedema (five patients [55.6%]) and anaphylaxis (four patients [44.4%]). Allergic reactions occurred within the first 15 minutes of ingesting camel's milk in all the patients (100%). Concurrent allergies were observed in 77.8% of the patients, of whom, five patients (71.4%) had atopic dermatitis (AD) and two patients (22%) had cow's milk allergy that exacerbated AD. All the patients (100%) had a family history of allergies. The family farm was the source of camel's milk in all the patients (100%). The WBC count was 9425 ± 1452.8 (mean ± SD) cells/μL, and eosinophils was 612 ± 455.4 (mean ± SD) cells/μL, and the median IgE was 301.5 kU/mL. A camel's milk SPT resulted in a wheal of 8.7 ± 4.9 (mean ± SD) mm.

CONCLUSION

Camel's milk allergy is a distinct, yet very rare, disease entity. Cutaneous and systemic allergic reactions are the main clinical manifestations. Concomitant other allergies, viz., AD, and positive family history are risk factors. Early life exposure to camel's milk is a possible risk factor. High blood eosinophil counts and total IgE levels were observed in patients with camel's milk allergy. In the presence of a consistent and specific clear-cut history of camel's milk-related symptoms, a SPT was a dependable confirmatory test.

Allergic diseases among children: nutritional prevention and intervention

Allergic diseases comprise a genetically heterogeneous group of chronic, immunomediated diseases. It has been clearly reported that the prevalence of these diseases has been on the rise for the last few decades, but at different rates, in various areas of the world. This paper discusses the epidemiology of allergic diseases among children and their negative impact on affected patients, their families, and societies. These effects include the adverse effects on quality of life and economic costs. Medical interest has shifted from tertiary or secondary prevention to primary prevention of these chronic diseases among high-risk infants in early life. Being simple, practical, and cost-effective are mandatory features for any candidate methods delivering these strategies. Dietary therapy fits this model well, as it is simple, practical, and cost-effective, and involves diverse methods. The highest priority strategy is feeding these infants breast milk. For those who are not breast-fed, there should be a strategy to maintain beneficial gut flora that positively influences intestinal immunity. We review the current use of probiotics, prebiotics, and synbiotics, and safety and adverse effects. Other dietary modalities of possible potential in achieving this primary prevention, such as a Mediterranean diet, use of milk formula with modified (hydrolyzed) proteins, and the role of micronutrients, are also explored. Breast-feeding is effective in reducing the risk of asthma, allergic rhinitis, and atopic eczema among children. In addition, breast milk constitutes a major source of support for gut microbe colonization, due to its bifidobacteria and galactooligosaccharide content. The literature lacks consensus in recommending the addition of probiotics to foods for prevention and treatment of allergic diseases, while prebiotics may prove to be effective in reducing atopy in healthy children. There is insufficient evidence to support soy formulas or amino acid formulas for prevention of allergic disease. A healthy diet, such as the Mediterranean diet, may have a protective effect on the development of asthma and atopy in children. In children with asthma and allergic diseases, vitamin D deficiency correlates strongly with asthma, allergic rhinitis, and wheezing.

Non-truncating LIFR mutation: causal for prominent congenital pain insensitivity phenotype with progressive vertebral destruction?

We present a Qatari family with two children who displayed a characteristic phenotype of congenital marked pain insensitivity with hypohidrosis and progressive aseptic destruction of joints and vertebrae resembling that of hereditary sensory and autonomic neuropathies (HSANs). The patients, aged 10 and 14, remained of uncertain genetic diagnosis until whole genome sequencing was pursued. Genome sequencing identified a novel homozygous C65S mutation in the LIFR gene that is predicted to markedly destabilize and alter the structure of a particular domain and consequently to affect the functionality of the whole multi-domain LIFR protein. The C65S mutant LIFR showed altered glycosylation and an elevated expression level that might be attributed to a slow turnover of the mutant form. LIFR mutations have been reported in Stüve-Wiedemann syndrome (SWS), a severe autosomal recessive skeletal dysplasia often resulting in early death. Our patients share some clinical features of rare cases of SWS long-term survivors; however, they also phenocopy HSAN due to the marked pain insensitivity phenotype and progressive bone destruction. Screening for LIFR mutations might be warranted in genetically unresolved HSAN phenotypes.

Linear growth and endocrine function in children with ataxia telangiectasia

INTRODUCTION

Ataxia telangiectasia (AT) is a rare, genetic, primary immune deficiency disease characterized by immunodeficiency and neurological manifestations, with an increased tendency to infection, malignancy, and autoimmune diseases. Both growth delay and endocrine abnormalities are occasionally reported in these patients.

PATIENTS AND METHODS

We studied growth parameters height (Ht), weight, body mass index (BMI) and calculated the Ht standard deviation scores (HtSDS) of 13 patients (age 7.7 ± 3.5 years-age range: 3-14.5 years) with AT in relation to their mid-parental Ht SDS (MPHtSDS). We measured their serum calcium (Ca), phosphorus (PO4), alkaline phosphatase, alanine transferase (ALT), serum ferritin, creatinine and albumin concentrations. Endocrine investigations included the assessment of serum free thyroxine (FT4), thyrotropin (TSH), insulin-like growth factor-I (IGF-I) and morning cortisol. Complete blood count and serum immunoglobulins (IgG, IgM and IgA antibodies) were also measured. Growth data were correlated to hormonal and immune data.

RESULTS

About 31% of patients with AT had short stature (HtSDS <-2). However, their MPHtSDS denoted that their short stature was familial because four out of 13 had MPHtSDS <-2. They had low BMI, and two of them had low serum albumin and IGF-I, denoting malnutrition or disturbed growth hormone secretion. Elevated serum ALT and ferritin in some patients suggest immune-related inflammation in the liver. 30% of patients had high TSH, two of them had low FT4 diagnosing overt (15%) and sub-clinical (15%) hypothyroidism. Anti-thyroid peroxidase antibodies were high in two out of 13 patients denoting immune-related thyroid aggression. Eight out of 13 patients had Vitamin D deficiency (<20 ng/ml) however, their serum Ca and PO4 levels were in the normal range. One adolescent girl (14.5 years) had hyper-gonadotropic hypogonadism (low estradiol and high follicle stimulating hormone). All patients had normal 8 AM cortisol and renal function. None of the growth parameters were correlated with the IgG, IgM or IgA levels.

IN SUMMARY

Patients with AT had a high prevalence of growth retardation and endocrine dysfunction in the form of low IGF-I, overt and subclinical hypothyroidism and hypogonadism. Physicians should be aware of these possible endocrinopathies for an early diagnosis and proper treatment.

Co-existing paradoxical vocal cord motion and asthma in a young child

We are reporting a 7½-year-old child who had coexisting paradoxical vocal cord motion (PVCM) and asthma. There are only a few reported cases of PVCM in children younger than 10 years of age. Thus diagnosis mainly relies on high index of suspicion for these children. Missing PVCM diagnosis can lead to unnecessary diagnostic and therapeutic interventions to control asthma. We hope that this case report would increase the awareness of such coexistence in such a young age group.

Camel milk is a safer choice than goat milk for feeding children with cow milk allergy

Background. Various sources of mammalian milk have been tried in CMA. Objectives. To determine whether camel milk is safer than goat milk in CMA. Methods. Prospective study conducted at Hamad Medical Corporation between April 2007 and April 2010, on children with CMA. Each child had medical examination, CBC, total IgE, cow milk-specific IgE and SPT. CMA children were tested against fresh camel and goat milks. Results. Of 38 children (median age 21.5 months), 21 (55.3%) presented with urticaria, 17 (39.5%) atopic dermatitis, 10 (26.3%) anaphylaxis. WBC was 10, 039 ± 4, 735 cells/μL, eosinophil 1, 143 ± 2, 213 cells/μL, IgE 694 ± 921 IU/mL, cow's milk-specific-IgE 23.5 ± 35.6 KU/L. Only 7 children (18.4%) tested positive to camel milk and 24 (63.2%) to goat milk. 6 (15.8%) were positive to camel, goat, and cow milks. Patients with negative SPT tolerated well camel and goat milks. Conclusions. In CMA, SPT indicates low cross-reactivity between camel milk and cow milk, and camel milk is a safer alternative than goat milk.

Increased circulating levels of soluble HLA class I heterodimers in patients with sickle cell disease

This study examined the presence of a persistent state of low-grade inflammation in sickle cell anemia patients by measuring circulating sHLA-I heterodimers and C-reactive protein during the steady state and after recent crises. Thirty-nine pediatric sickle hemoglobinopathy patients were studied during the steady state and 11 patients were evaluated within 1 month of a painful crisis. A disease severity score was generated for each patient, and soluble HLA-I (sHLA-I) and C-reactive protein levels were determined. Soluble HLA-I was significantly elevated in 55% of the steady-state group and in 36% of the recent-crisis group. The percentage of patients with elevated sHLA-I differed in the various disease subgroups in the steady state: 46% of Hb SS patients, 70% of Hb SC patients, 75% of Hb S beta-thal patients, and 20% of Hb SSF patients. Steady-state and recent-crisis sHLA-I levels were not significantly different. C-reactive protein levels were elevated in 11% of steady-state patients and in 9% of recent-crisis patients. Soluble HLA-I levels did not correlate with C-reactive protein levels or disease severity score, age, hemoglobin, reticulocyte count, platelet count, or white cell count. These results show that the majority of sickle hemoglobinopathy patients have elevated sHLA-I levels during the steady state and after recent crisis, suggesting the presence of chronic inflammation during the steady state.

Elevated levels of soluble HLA class I (sHLA-I) in children with severe atopic dermatitis

BACKGROUND

Atopic dermatitis is characterized by increased production of IgE and interleukin-4, immediate skin test reactivity to allergens, increased expression of CD23 on mononuclear cells, and decreased production of interferon-gamma. Soluble HLA-I molecule levels are elevated in conditions where T cells are activated such as viral infections, autoimmune diseases, and organ transplantation.

OBJECTIVE

We wished to determine if sHLA-I heterodimers were also elevated in patients with atopic dermatitis and if sHLA-I elevations correlated with disease activity.

METHODS

Fourteen children with atopic dermatitis resistant to conventional treatment were followed over an 8-week period during an ongoing trial of treatment with topical sodium cromoglycate. Extent of skin involvement, disease severity, absolute eosinophil counts, IgE and HLA-I levels were determined at the time of enrollment into the study. Additional sHLA-I levels were measured after 4 and 8 weeks of therapy.

RESULTS

Mean sHLA-I levels were significantly elevated in atopic dermatitis patients, 2.07 +/- 1.14 versus 1.00 +/- 0.22 microg/mL in controls (P < .0001). Nine of 14 patients (64%) had elevated sHLA-I antigens. Soluble HLA-I levels did not correlate with the extent of disease, disease severity score, eosinophil count, or IgE levels. There was a remarkable consistency in sHLA-I levels at baseline and after 4 and 8 weeks of therapy, even with significant clinical improvement.

CONCLUSION

We conclude that sHLA-I heterodimers are elevated in 64% of our patients with atopic dermatitis and that elevations persist after clinically effective therapy. This conclusion supports recommendations for prolonged preventative and treatment measures in this atopic disease.

Care of asthma: allergy clinic versus emergency room

BACKGROUND

Demographic and socioeconomic factors have an impact upon the morbidity and mortality rates of asthma in inner-city pediatric populations. Many pediatric patients with asthma use the emergency room as their primary care physician, while a smaller number of children with asthma use the allergy-immunology clinic.

OBJECTIVE

We examined the demographic and socioeconomic characteristics of asthmatic patients using the emergency room as their primary care physician and of those attending the allergy-immunology clinic in the same inner-city hospital. We compared the morbidity and cost of care of asthmatic patients who received their medical care in the emergency room to that of those who received their care in the allergy-immunology clinic.

METHODS

Fifty consecutive emergency room patients and 25 clinic patients were studied using an identical questionnaire.

RESULTS

There was no difference between the two groups in the total number of individuals per household, children per family, monthly income, type or size of dwelling, financial problems purchasing medications, health insurance type, distance to the medical center, or education of the caretaker. Severity of asthma was not different in the two groups before the start of the study. The only significant demographic difference was in age: 10.6 years for the clinic group and 7.8 years for the emergency room group (P < .002). Clinically, in the year preceding the interview, the clinic group had significantly less nocturnal cough (P < .025), sleep interruption (P < .001), weekly asthma (P < .05), and emergency room visits (P < .09). The allergy clinic group had an approximate average savings of $137 per patient per year. Hospital admissions and emergency room costs were increased by a small group of three allergy clinic patients, decreasing the difference in the cost of care between the two groups.

CONCLUSION

The data showed that patients who attended the emergency room and those who attended the allergy-immunology clinic were not demographically or socioeconomically different. The decreased morbidity of asthma and cost of care for the allergy clinic patients, as opposed to the emergency room patients, are likely due to the care given in the allergy-immunology clinic.

New concepts in the immunology of sickle cell disease

OBJECTIVE

Our objective is to review the role of adhesion molecules, cytokines, and inflammation in the abnormal adherence of sickle red blood cells to vascular endothelia in the pathogenesis of vascular complication in patients with sickle cell anemia.

DATA SOURCES

The MEDLINE database was used to review the hematologic, immunologic, and allergy literature in English with respect to the adhesion molecules involved in sickle hematopoiesis and vascular complications.

STUDY SELECTION

Studies selected for review were those that identified the adhesion molecules involved in reticulocyte-endothelial adhesion and the influence that cytokines, infections, and atopy have upon the expression of these molecules.

RESULTS

In sickle cell disease, a constant low level of inflammation caused by abnormal adhesion of sickle erythrocytes to endothelial cells in the microvasculature produces low-level tissue ischemia. Allergic and infectious inflammations are likely to lead to increased sickle erythrocyte trapping in the microvascular endothelia which progresses to vessel obstruction, end organ ischemic damage, and dysfunction.

CONCLUSION

The identification of underlying immune defects that predispose patients to infections and inflammation needs to be emphasized. Anti-inflammatory medications, anti-adhesion molecule monoclonal antibodies, and adhesion molecule binding-site analogs may have a future in the treatment of the acute vascular complications of sickle cell disease.

Recurrent wheezing in children with respiratory syncytial virus (RSV) bronchiolitis in Qatar

Records of 70 infants admitted to Hamad General Hospital with RSV bronchiolitis and a similar number of controls were retrospectively reviewed. Two years after admission, 44% of the infants with RSV bronchiolitis developed recurrent wheezing compared with only 12.9% of controls (P = 0.001). A family history of atopy appeared not to be a significant predisposing factor for the occurrence of recurrent wheezing in post RSV bronchiolitis patients. These results are similar to those from similar studies in industrialized countries.