Effect of lockdowns on the epidemiology of pediatric respiratory disease-A retrospective analysis of the 2021 summer epidemic

BACKGROUND

The imposition of lockdowns during the severe acute respiratory syndrome coronavirus-2 pandemic led to a significant decrease in pediatric care utilization in 2020. After restrictions were loosened, a surge in pediatric respiratory disease was observed in pediatric wards. The aim of this study was to quantify the effect of the lockdown(s) on the incidence of pediatric respiratory disease.

METHODS

For this multicenter retrospective study, emergency department (ED) visit and admission data between January 2017 and September 2021 was collected from eight general hospitals in the Netherlands. Clinical diagnoses were extracted and categorized in groups ("communicable infectious disease," "all respiratory infections," "upper respiratory tract infection," "lower respiratory tract infection," and "asthma/preschool wheezing"). The incidence of admissions and ED visits during 2020 and 2021 was compared to the incidence in 2017-2019.

RESULTS

Successive lockdowns resulted in a maximum decrease of 61% and 57% in ED visits and admissions, respectively. After loosening restrictions during the summer of 2021, a 48% overall increase in ED visits and 31% overall increase in admission numbers was observed in July compared to the average July in 2017-2019. This was explained by a 381% increase in ED visits and a 528% increase in ward admissions due to overall respiratory infections, mainly due to lower respiratory tract infections.

CONCLUSIONS

Successive lockdowns in the spring and winter of 2020 and 2021 led to a decreased incidence of communicable infections, especially respiratory tract infections. The resulting lack of pediatric immunity resulted in an off-season surge in care utilization at an unexpected moment.

Adverse effect of lockdowns during the COVID-19 pandemic: increased incidence of pediatric crisis admissions due to eating disorders and adolescent intoxications

During the COVID-19 pandemic, countries imposed (partial) lockdowns that reduced viral transmission. However, these interventions may have unfavorable effects on emotional and psychological well-being. The aim of this study was to quantify possible adverse effects of the COVID-19 pandemic on psychological wellbeing in children and adolescents. Hospital admission data between January 2017 and September 2021 from eight general hospitals in the Netherlands was collected, comparing the incidences of sub-categorized psychological diagnoses, more specifically eating disorders, intentional intoxications, accidental intoxications, and excessive crying, before (2017-2019) and during the pandemic (2020-2021). Data was summarized per month and per year, and the years 2020 and 2021 were compared to 2017-2019. The relative increase or decrease in diagnoses since the start of the pandemic was calculated. Overall pediatric hospital admissions decreased with 28% since the start of the pandemic. Non-infectious diagnoses showed a decrease of 8%. Of these non-infectious diagnoses, overall psychosocial admissions were increased (+ 9%), mostly caused by an increase in admissions for eating disorders (+ 64%) and intoxications in adolescents (+ 24%). In addition, the proportion of admissions due to psychosocial diagnoses increased post-pandemic (6% vs 4%, p < 0.001). Overall admissions for intoxications in children (- 3%) and excessive crying (- 1%) did not increase, although peaks in incidence were found at the start of the second lockdown.

CONCLUSION

During the COVID-19 pandemic, admission rates for eating disorders and intentional intoxications showed a substantial increase, indicating a high burden of pediatric psychiatric diseases.

WHAT IS KNOWN

• The COVID-19 pandemic has had an impact on psychosocial wellbeing in children and adolescents.

WHAT IS NEW

• There was an increase in admissions due to psychosocial problems in the Netherlands in the period after the pandemic. • This was mainly caused by an increase in crisis admissions due to eating disorders and intoxications in adolescents.

The impact of lockdown on pediatric ED visits and hospital admissions during the COVID19 pandemic: a multicenter analysis and review of the literature

The coronavirus disease 2019 pandemic has enormous impact on society and healthcare. Countries imposed lockdowns, which were followed by a reduction in care utilization. The aims of this study were to quantify the effects of lockdown on pediatric care in the Netherlands, to elucidate the cause of the observed reduction in pediatric emergency department (ED) visits and hospital admissions, and to summarize the literature regarding the effects of lockdown on pediatric care worldwide. ED visits and hospital admission data of 8 general hospitals in the Netherlands between January 2016 and June 2020 were summarized per diagnosis group (communicable infections, noncommunicable infections, (probable) infection-related, and noninfectious). The effects of lockdown were quantified with a linear mixed effects model. A literature review regarding the effect of lockdowns on pediatric clinical care was performed. In total, 126,198 ED visits and 47,648 admissions were registered in the study period. The estimated reduction in general pediatric care was 59% and 56% for ED visits and admissions, respectively. The largest reduction was observed for communicable infections (ED visits: 76%; admissions: 77%), whereas the reduction in noninfectious diagnoses was smaller (ED visits 36%; admissions: 37%). Similar reductions were reported worldwide, with decreases of 30-89% for ED visits and 19-73% for admissions.Conclusion: Pediatric ED utilization and hospitalization during lockdown were decreased in the Netherlands and other countries, which can largely be attributed to a decrease in communicable infectious diseases. Care utilization for other conditions was decreased as well, which may indicate that care avoidance during a pandemic is significant. What is Known: • The COVID-19 pandemic had enormous impact on society. • Countries imposed lockdowns to curb transmission rates, which were followed by a reduction in care utilization worldwide. What is New: • The Dutch lockdown caused a significant decrease in pediatric ED utilization and hospitalization, especially in ED visits and hospital admissions because of infections that were not caused by SARS-CoV-2. • Care utilization for noninfectious diagnoses was decreased as well, which may indicate that pediatric care avoidance during a pandemic is significant.

The influence of chest X-ray results on antibiotic prescription for childhood pneumonia in the emergency department

The aim of this study is to evaluate the influence of chest X-ray (CXR) results on antibiotic prescription in children suspected of lower respiratory tract infections (RTI) in the emergency department (ED). We performed a secondary analysis of a stepped-wedge, cluster randomized trial of children aged 1 month to 5 years with fever and cough/dyspnoea in 8 EDs in the Netherlands (2016-2018), including a 1-week follow-up. We analysed the observational data of the pre-intervention period, using multivariable logistic regression to evaluate the influence of CXR result on antibiotic prescription. We included 597 children (median age 17 months [IQR 9-30, 61% male). CXR was performed in 109/597 (18%) of children (range across hospitals 9 to 50%); 52/109 (48%) showed focal infiltrates. Children who underwent CXR were more likely to receive antibiotics, also when adjusted for clinical signs and symptoms, hospital and CXR result (OR 7.25 [95% CI 2.48-21.2]). Abnormalities on CXR were not significantly associated with antibiotic prescription.Conclusion: Performance of CXR was independently associated with more antibiotic prescription, regardless of its results. The limited influence of CXR results on antibiotic prescription highlights the inferior role of CXR on treatment decisions for suspected lower RTI in the ED. What is Known: • Chest X-ray (CXR) has a high inter-observer variability and cannot distinguish between bacterial or viral pneumonia. • Current guidelines recommend against routine use of CXR in children with uncomplicated respiratory tract infections (RTIs) in the outpatient setting. What is New: • CXR is still frequently performed in non-complex children suspected of lower RTIs in the emergency department • CXR performance was independently associated with more antibiotic prescriptions, regardless of its results, highlighting the inferior role of chest X-rays in treatment decisions.

Evaluation of a clinical decision rule to guide antibiotic prescription in children with suspected lower respiratory tract infection in The Netherlands: A stepped-wedge cluster randomised trial

BACKGROUND

Optimising the use of antibiotics is a key component of antibiotic stewardship. Respiratory tract infections (RTIs) are the most common reason for antibiotic prescription in children, even though most of these infections in children under 5 years are viral. This study aims to safely reduce antibiotic prescriptions in children under 5 years with suspected lower RTI at the emergency department (ED), by implementing a clinical decision rule.

METHODS AND FINDINGS

In a stepped-wedge cluster randomised trial, we included children aged 1-60 months presenting with fever and cough or dyspnoea to 8 EDs in The Netherlands. The EDs were of varying sizes, from diverse geographic and demographic regions, and of different hospital types (tertiary versus general). In the pre-intervention phase, children received usual care, according to the Dutch and NICE guidelines for febrile children. During the intervention phase, a validated clinical prediction model (Feverkidstool) including clinical characteristics and C-reactive protein (CRP) was implemented as a decision rule guiding antibiotic prescription. The intervention was that antibiotics were withheld in children with a low or intermediate predicted risk of bacterial pneumonia (≤10%, based on Feverkidstool). Co-primary outcomes were antibiotic prescription rate and strategy failure. Strategy failure was defined as secondary antibiotic prescriptions or hospitalisations, persistence of fever or oxygen dependency up to day 7, or complications. Hospitals were randomly allocated to 1 sequence of treatment each, using computer randomisation. The trial could not be blinded. We used multilevel logistic regression to estimate the effect of the intervention, clustered by hospital and adjusted for time period, age, sex, season, ill appearance, and fever duration; predicted risk was included in exploratory analysis. We included 999 children (61% male, median age 17 months [IQR 9 to 30]) between 1 January 2016 and 30 September 2018: 597 during the pre-intervention phase and 402 during the intervention phase. Most children (77%) were referred by a general practitioner, and half of children were hospitalised. Intention-to-treat analyses showed that overall antibiotic prescription was not reduced (30% to 25%, adjusted odds ratio [aOR] 1.07 [95% CI 0.57 to 2.01, p = 0.75]); strategy failure reduced from 23% to 16% (aOR 0.53 [95% CI 0.32 to 0.88, p = 0.01]). Exploratory analyses showed that the intervention influenced risk groups differently (p < 0.01), resulting in a reduction in antibiotic prescriptions in low/intermediate-risk children (17% to 6%; aOR 0.31 [95% CI 0.12 to 0.81, p = 0.02]) and a non-significant increase in the high-risk group (47% to 59%; aOR 2.28 [95% CI 0.84 to 6.17, p = 0.09]). Two complications occurred during the trial: 1 admission to the intensive care unit during follow-up and 1 pleural empyema at day 10 (both unrelated to the study intervention). Main limitations of the study were missing CRP values in the pre-intervention phase and a prolonged baseline period due to logistical issues, potentially affecting the power of our study.

CONCLUSIONS

In this multicentre ED study, we observed that a clinical decision rule for childhood pneumonia did not reduce overall antibiotic prescription, but that it was non-inferior to usual care. Exploratory analyses showed fewer strategy failures and that fewer antibiotics were prescribed in low/intermediate-risk children, suggesting improved targeting of antibiotics by the decision rule.

TRIAL REGISTRATION

Netherlands Trial Register NTR5326.

[Group A streptococcal-associated arthritis in children]

Group A streptococcal (GAS) infection can cause septic arthritis (SA), acute rheumatic fever (ARF) and post-streptococcal reactive arthritis (PSRA). Differentiating between these three entities can have important consequences for both therapy and prognosis. SA is diagnosed by means of clinical, biochemical and microbiological parameters. With respect to ARF and PSRA, evidence of a recent GAS infection should be established, in combination with several other major or minor criteria. Currently there is ongoing scientific debate as to whether PSRA and ARF are two different disease entities or belong to the same spectrum. PSRA presents earlier after GAS pharyngitis than ARF, is normally less responsive to NSAIDs, has a longer duration and is often accompanied by skin abnormalities. However, there are also many similarities. In this report we describe three children suffering from GAS-associated arthritis and discuss the symptoms, diagnosis and therapy.

[Neonatal sepsis caused by group B streptococci: atypical and recurrent disease episodes]

Both neonates of male twins born at 30 weeks and 3 days gestation presented with late-onset sepsis caused by an infection with group B streptococci (GBS), shortly after one another. Although the younger twin recovered with a standard regimen of 10 days penicillin G i.v., the older twin had three recurrent episodes with GBS positive blood cultures. Oropharyngeal, faecal, urine, liquor and breast milk cultures were GBS negative. Using echocardiography and a PET/CT scan, a persistent endovascular focus was discovered. We treated him with penicillin G i.v. for 4 weeks, after which he recovered completely. Another male neonate born at 26 weeks gestation presented with GBS sepsis and developed an erythematous swelling of the right mandibula within 12 hours. Ultrasound revealed parotitis, which is rare in neonates (3.8 per 10,000). Risk factors for parotitis include prematurity, low birth weight and dehydration (i.e., diuretic usage). Parotitis can be complicated by abscess formation.

Ataxia-telangiectasia patients presenting with hyper-IgM syndrome

Ataxia-telangiectasia (A-T) is characterised by progressive neurological abnormalities, oculocutaneous telangiectasias and immunodeficiency (decreased serum IgG subclass and/or IgA levels and lymphopenia). However, 10% of A-T patients present with decreased serum IgG and IgA with normal or raised IgM levels. As cerebellar ataxia and oculocutaneous telangiectasias are not present at very young age, these patients are often erroneously diagnosed as hyper IgM syndrome (HIGM). Eight patients with A-T, showing serum Ig levels suggestive of HIGM on first presentation, are described. All had decreased numbers of T lymphocytes, unusual in HIGM. The diagnosis A-T was confirmed by raised alpha-fetoprotein levels in all patients. To prevent mistaking A-T patients for HIGM it is proposed to add DNA repair disorders as a possible cause of HIGM.

Diagnosing mycobacterial lymphadenitis in children using fine needle aspiration biopsy: cytomorphology, ZN staining and autofluorescence -- making more of less

Although the incidence of TB has stabilized or declined in most world regions, it is increasing in Africa, Southeast Asia, and the Eastern Mediterranean, fuelled by the HIV pandemic. More than 4,000 people died daily from TB-related illnesses in 2005. TB is a major cause of childhood morbidity and mortality in these developing countries, and there is an urgent need for rapid and definitive modalities for mycobacterial diagnosis in children. This prospective study in Tygerberg Hospital, Cape Town, South Africa, evaluates the ability of fine needle aspiration biopsy (FNAB) to diagnose mycobacterial lymphadenitis in children, using cytomorphology, autofluorescence on Papanicolaou stained smears, Ziehl-Nielsen (ZN) staining and/or culture. FNABs were performed on 200 children, and 25 (12.5%) aspirates were inadequate. Cultures were positive in 79/175 (45%); Mycobacterium tuberculosis was identified in 61 and Mycobacterium bovis BCG in 18 cases. Using culture as the gold standard, the concordance of the different techniques was as follows: cytomorphology 70%, ZN staining 73%, and autofluorescence 68%. Using an alternative gold standard (culture positive and/or suggestive cytomorphology plus positive autofluorescence or ZN smear), the "true" diagnostic performance of the various techniques was as follows: cytomorphology-sensitivity 78%, specificity 91%, positive predictive value (PPV) 93%, ZN staining - sensitivity 62%%, specificity 97%, PPV 97%; autofluorescence-sensitivity 67%, specificity 97%, PPV 97%; and culture-sensitivity 75%, specificity 100%, and PPV 100%. FNAB was shown to provide a rapid and definitive diagnosis in the majority of cases of suspected tuberculous lymphadenitis in children, based on cytomorphology and identification of the organism.

Two patients with complete defects in interferon gamma receptor-dependent signaling

Unusual susceptibility to mycobacterial infections can be caused by deleterious mutations in genes that encode the interferon-gamma receptor 1 chain. Such mutations hamper the activation of macrophages by a type 1 immune response and result in enhanced survival of intracellular pathogens. We here report two patients with unusual mycobacterial infections, both diagnosed with homozygous deleterious interferon-gamma receptor 1 gene mutations. Patient 1 became ill after Bacillus Calmette-Guérin vaccination at the age of 9 months and died at the age of 18 months. She carried a homozygous C71Y mutation in the extracellular part of the mature interferon-gamma receptor 1 protein, resulting in the lack of detectable protein expression and absence of interferon-gamma dependent signaling. Patient 2 became ill at the age of 3 years, is still alive at 19 years of age, and has suffered from five successive infection episodes with atypical mycobacteria. A homozygous splice-site mutation in intron 3 was identified, resulting in the deletion of exon 3 at the mRNA level and consequently a truncated interferon-gamma receptor 1 protein with absence of the transmembrane domain. Protein expression and interferon-gamma dependent signaling were not detectable.

Human T-cell lines with well-defined T-cell receptor gene rearrangements as controls for the BIOMED-2 multiplex polymerase chain reaction tubes

The BIOMED-2 multiplex polymerase chain reaction (PCR) tubes for analysis of immunoglobulin and T-cell receptor (TCR) gene rearrangements have recently been introduced as a reliable and easy tool for clonality diagnostics in suspected lymphoproliferations. Quality and performance assessment of PCR-based clonality diagnostics is generally performed using human leukemia/lymphoma cell lines as controls. We evaluated the utility of 30 well-defined human T-cell lines for quality performance testing of the BIOMED-2 PCR primers and protocols. The PCR analyses of the TCR loci were backed up by Southern blot analysis. The clonal TCRB, TCRG and TCRD gene rearrangements were analyzed for gene segment usage and for the size and composition of their junctional regions. In 29 out of 30 cell lines, unique clonal TCR gene rearrangements could be easily detected. Besides their usefulness in molecular clonality diagnostics, these cell lines can now be authenticated based on their TCR gene rearrangement profile. This enables their correct use in molecular clonality diagnostics and in other cancer research studies.

[Widely divergent clinical phenotype of x-linked agammaglobulinemia in two cousins]

X-linked agammaglobulinaemia (XLA) is a primary immunodeficiency caused by a mutation in the gene encoding Bruton's tyrosine kinase (BTK). The classical presentation of XLA consists of the almost complete absence of B-lymphocytes and immunoglobulins in the peripheral blood leading to severe, mainly bacterial, upper and lower respiratory-tract infections already in early childhood. Irrespective of the kind of BTK-gene mutation the phenotype of XLA can be very diverse. Two 9-year-old cousins with the same BTK-gene mutation illustrate this phenotypical diversity. One boy had a classical presentation and was on maintenance treatment with intravenous immunoglobulins and prophylactic antibiotics to control his infections. Without any prophylactic treatment, his cousin had no abnormal infectious course despite very low B-lymphocyte counts and immunoglobulin levels in the blood. The mechanisms underlying the phenotypical diversity of XLA have not been clarified. Gene polymorphisms affecting the innate immune system may play a role.

Radiosensitive SCID patients with Artemis gene mutations show a complete B-cell differentiation arrest at the pre-B-cell receptor checkpoint in bone marrow

Severe combined immunodeficiency disease (SCID) can be immunologically classified by the absence or presence of T, B, and natural killer (NK) cells. About 30% of T(-)B(-)NK(+) SCID patients carry mutations in the recombination activating genes (RAG). Some T(-)B(-)NK(+) SCID patients without RAG gene mutations are sensitive to ionizing radiation, and several of these radiosensitive (RS) SCID patients were recently shown to have large deletions or truncation mutations in the Artemis gene, implying a role for Artemis in DNA double-strand break (dsb) repair. We identified 5 RS-SCID patients without RAG gene mutations, 4 of them with Artemis gene mutations. One patient had a large genomic deletion, but the other 3 patients carried simple missense mutations in conserved amino acid residues in the SNM1 homology domain of the Artemis protein. Extrachromosomal V(D)J recombination assays showed normal and precise signal joint formation, but inefficient coding joint formation in fibroblasts of these patients, which could be complemented by the wild-type Artemis gene. The cells containing the missense mutations in the SNM1 homology domain had the same recombination phenotype as the cells with the large deletion, indicating that these amino acid residues are indispensable for Artemis function. Immunogenotyping and immunophenotyping of bone marrow samples of 2 RS-SCID patients showed the absence of complete V(H)-J(H) gene rearrangements and consequently a complete B-cell differentiation arrest at the pre-B-cell receptor checkpoint-that is, at the transition from CyIgmu(-) pre-B-I cells to CyIgmu(+) pre-B-II cells. The completeness of this arrest illustrates the importance of Artemis at this stage of lymphoid differentiation.

The immunophenotypic and immunogenotypic B-cell differentiation arrest in bone marrow of RAG-deficient SCID patients corresponds to residual recombination activities of mutated RAG proteins

The protein products of the recombination activating genes (RAG1 and RAG2) initiate the formation of immunoglobulin (Ig) and T-cell receptors, which are essential for B- and T-cell development, respectively. Mutations in the RAG genes result in severe combined immunodeficiency disease (SCID), generally characterized by the absence of mature B and T lymphocytes, but presence of natural killer (NK) cells. Biochemically, mutations in the RAG genes result either in nonfunctional proteins or in proteins with partial recombination activity. The mutated RAG genes of 9 patients from 7 families were analyzed for their recombination activity using extrachromosomal recombination substrates, rearrangement of endogenous Ig loci in RAG gene-transfected nonlymphoid cells, or the presence of Ig gene rearrangements in bone marrow (BM). Recombination activity was virtually absent in all 6 patients with mutations in the RAG core domains, but partial activity was present in the other 3 RAG-deficient patients, 2 of them having Omenn syndrome with oligoclonal T lymphocytes. Using 4-color flow cytometry, we could define the exact stage at which B-cell differentiation was arrested in the BM of 5 RAG-deficient SCID patients. In 4 of 5 patients, the absence of recombination activity was associated with a complete B-cell differentiation arrest at the transition from cytoplasmic (Cy) Igmu(-) pre-B-I cells to CyIgmu(+) pre-B-II cells. However, the fifth patient showed low frequencies of precursor B cells with CyIgmu and surface membrane IgM, in line with the partial recombination activity of the patient's mutated RAG gene and the detection of in-frame Ig gene rearrangements in BM.

XLA patients with BTK splice-site mutations produce low levels of wild-type BTK transcripts

X-linked agammaglobulinemia is caused by mutations in the BTK gene, which result in a precursor B-cell differentiation arrest in the bone marrow and the absence of or strongly reduced B lymphocytes in blood. We identified a patient with a mild clinical phenotype, low numbers of B lymphocytes, and a splice-site mutation in the BTK gene. The precursor B-cell compartment in the bone marrow of this patient was almost identical to that in healthy children. Using real-time quantitative polymerase chain reaction, we were able to detect low levels of wild-type BTK transcripts in his granulocytes. Therefore, we speculated that wild-type BTK transcripts might be responsible for a milder clinical and immunological phenotype, as has been shown in several other diseases. Consequently, we quantified the expression of wild-type BTK transcripts in granulocytes of eight additional patients with splice-site mutations and compared their phenotypes with 17 patients with other types of BTK mutations. In these eight patients, the presence of low levels of wild-type BTK transcripts did not show a clear correlation with the percentage, absolute number, or immunophenotype of B lymphocytes nor with age or serum immunoglobulin levels at diagnosis. Nevertheless, we postulate that the presence of wild-type BTK transcripts can be one of the many factors that influence the clinical and immunological phenotype in X-linked agammaglobulinemia.

Composition of precursor B-cell compartment in bone marrow from patients with X-linked agammaglobulinemia compared with healthy children

X-linked agammaglobulinemia (XLA) is characterized by a severe B-cell deficiency, resulting from a differentiation arrest in the bone marrow (BM). Because XLA is clinically and immunologically heterogeneous, we investigated whether the B-cell differentiation arrest in BM of XLA patients is heterogeneous as well. First, we analyzed BM samples from 19 healthy children by flow cytometry. This resulted in a normal B-cell differentiation model with eight consecutive stages. Subsequently, we analyzed BM samples from nine XLA patients. Eight patients had amino acid substitutions in the Bruton's tyrosine kinase (BTK) domain or premature stop codons, resulting in the absence of functional BTK proteins. In seven of these eight patients a major differentiation arrest was observed at the transition between cytoplasmic Ig(mu-) pre-B-I cells and cytoplasmic Ig(mu+) pre-B-II cells, consistent with a role for BTK in pre-B-cell receptor signaling. However, one patient exhibited a very early arrest at the transition between pro-B cells and pre-B-I cells, which could not be explained by a different nature of the BTK mutation. We conclude that the absence of functional BTK proteins generally leads to an almost complete arrest of B-cell development at the pre-B-I to pre-B-II transition. The ninth XLA patient had a splice site mutation associated with the presence of low levels of wild-type BTK mRNA. His BM showed an almost normal composition of the precursor B-cell compartment, suggesting that low levels of BTK can rescue the pre-B-cell receptor signaling defect, but do not lead to sufficient numbers of mature B lymphocytes in the peripheral blood.

Reviewing Omenn syndrome

Omenn syndrome is a form of severe combined immunodeficiency associated with high mortality. Early recognition is required in order to initiate life-saving therapy. This review provides information on the clinical symptoms, laboratory parameters and pathology of the disease, supporting early diagnosis in suspected patients. A literature search was performed using Medline, encompassing the period 1965-1999. Sixty-seven cases were identified and with the addition of a recently diagnosed patient at our hospital, 68 children were included. Median age at onset of symptoms was 4 weeks. Key symptoms were erythematous rash (98%), hepatosplenomegaly (88%), lymphadenopathy (80%), often accompanied by recurrent infections (72%) and alopecia (57%). An elevated WBC (55%) was frequently observed, due to eosinophilia and/or lymphocytosis. B-cell counts were significantly decreased whereas T-cell counts were elevated. A high serum IgE was another frequent finding (91%). Therapeutic options include bone marrow transplantation or cord blood stem cell transplantation; however, the mortality still was 46%.

CONCLUSION

Omenn syndrome is a fatal disease if untreated. The mortality may be reduced when diagnosis is established early and treatment is initiated rapidly by using early compatible bone marrow transplantation or cord blood stem cell transplantation.

Flow cytometric immunophenotyping in the diagnosis and follow-up of immunodeficient children

From time to time, paediatricians are confronted with children who might suffer from a primary immunodeficiency disease. For practical purposes, these children can be divided into four main clinical categories: (1) a relatively large group of children with recurrent ear-nose and throat and lower respiratory tract infections, in some cases caused by deficiencies of antibodies or complement; (2) children with failure to thrive, intractable diarrhoea or an opportunistic infection which can be caused by a T-lymphocyte or combined immunodeficiency; (3) children with infections with pyogenic bacteria or fungi as seen in case of granulocyte/monocyte function deficiency; and (4) a small heterogeneous group of children with recurrence of particular infections. Also, acquired immunodeficiency becomes a more common problem in paediatric practice. Flow cytometric immunophenotyping of leucocytes appears to be an efficient and rapid tool in the diagnosis and follow-up of immunodeficient patients, supporting early recognition, before serious infections have compromised the child's general condition. This technique can now be performed in many hospitals. In this review, we give directions for the use of flow cytometric immunophenotyping of leucocytes in the diagnosis and follow-up of immunodeficient children according to the four main clinical categories.

N-terminal truncated human RAG1 proteins can direct T-cell receptor but not immunoglobulin gene rearrangements

The proteins encoded by RAG1 and RAG2 can initiate gene recombination by site-specific cleavage of DNA in immunoglobulin and T-cell receptor (TCR) loci. We identified a new homozygous RAG1 gene mutation (631delT) that leads to a premature stop codon in the 5' part of the RAG1 gene. The patient carrying this 631delT RAG1 gene mutation died at the age of 5 weeks from an Omenn syndrome-like T(+)/B(- )severe combined immunodeficiency disease. The high number of blood T-lymphocytes (55 x 10(6)/mL) showed an almost polyclonal TCR gene rearrangement repertoire not of maternal origin. In contrast, B-lymphocytes and immunoglobulin gene rearrangements were hardly detectable. We showed that the 631delT RAG1 gene can give rise to an N-terminal truncated RAG1 protein, using an internal AUG codon as the translation start site. Consistent with the V(D)J recombination in T cells, this N-terminal truncated RAG1 protein was active in a plasmid V(D)J recombination assay. Apparently, the N-terminal truncated RAG1 protein can recombine TCR genes but not immunoglobulin genes. We conclude that the N-terminus of the RAG1 protein is specifically involved in immunoglobulin gene rearrangements.

BTKbase, mutation database for X-linked agammaglobulinemia (XLA)

X-linked agammaglobulinemia (XLA) is an immunodeficiency caused by mutations in the gene coding for Bruton's agammaglobulinemia tyrosine kinase (BTK). A database (BTKbase) of BTK mutations has been compiled and the recent update lists 463 mutation entries from 406 unrelated families showing 303 unique molecular events. In addition to mutations, the database also lists variants or polymorphisms. Each patient is given a unique patient identity number (PIN). Information is included regarding the phenotype including symptoms. Mutations in all the five domains of BTK have been noticed to cause the disease, the most common event being missense mutations. The mutations appear almost uniformly throughout the molecule and frequently affect CpG sites that code for arginine residues. The putative structural implications of all the missense mutations are given in the database. The improved version of the registry having a number of new features is available at http://www. helsinki.fi/science/signal/btkbase.html