Targeted Gene Sanger Sequencing Should Remain the First-Tier Genetic Test for Children Suspected to Have the Five Common X-Linked Inborn Errors of Immunity

To address inborn errors of immunity (IEI) which were underdiagnosed in resource-limited regions, our centre developed and offered free genetic testing for the most common IEI by Sanger sequencing (SS) since 2001. With the establishment of The Asian Primary Immunodeficiency (APID) Network in 2009, the awareness and definitive diagnosis of IEI were further improved with collaboration among centres caring for IEI patients from East and Southeast Asia. We also started to use whole exome sequencing (WES) for undiagnosed cases and further extended our collaboration with centres from South Asia and Africa. With the increased use of Next Generation Sequencing (NGS), we have shifted our diagnostic practice from SS to WES. However, SS was still one of the key diagnostic tools for IEI for the past two decades. Our centre has performed 2,024 IEI SS genetic tests, with in-house protocol designed specifically for 84 genes, in 1,376 patients with 744 identified to have disease-causing mutations (54.1%). The high diagnostic rate after just one round of targeted gene SS for each of the 5 common IEI (X-linked agammaglobulinemia (XLA) 77.4%, Wiskott–Aldrich syndrome (WAS) 69.2%, X-linked chronic granulomatous disease (XCGD) 59.5%, X-linked severe combined immunodeficiency (XSCID) 51.1%, and X-linked hyper-IgM syndrome (HIGM1) 58.1%) demonstrated targeted gene SS should remain the first-tier genetic test for the 5 common X-linked IEI.

Reliability of acute illness dihydrorhodamine-123 testing for chronic granulomatous disease

BACKGROUND

Dihydrorhodamine (DHR) flow cytometric analysis is used to evaluate granulocyte oxidative bursts and is the test of choice for the diagnosis of chronic granulomatous disease (CGD). We present the clinical and DHR test profiles of five subjects assessed during and after acute illness.

METHODS

This was a retrospective report of the findings of five out of a total of one hundred and seventeen patients, whose blood was sent to the laboratory for dihydrorhodamine-123 flow cytometry testing between January 2005 and December 2010. Using whole blood technique and stimulation using phorbol myristate acetate, the results of DHR were expressed as stimulation index and coefficient of variation of histograms of stimulated cells and compared with healthy controls. DHR tests were repeated when the patients had recovered and were clinically well.

RESULTS

These five patients showed abnormal DHR test results during their acute illness, with a stimulation index (SI) lower (p = 0.009) and coefficient of variation (CV) higher (p = 0.009) than controls. The DHR profiles repeated when patients had recovered showed normalization of tests with no significant difference for SI (p = 0.602) and CV (p = 0.917) compared to controls. Wilcoxon Signed Rank tests showed a significant improvement in SI (p = 0.043) and CV (p = 0.043) upon recovery. On follow up, all five patients were well, with no further severe or atypical infections.

CONCLUSIONS

DHR may be transiently abnormal during acute illness, and may therefore not be reliable when assessed during an acute illness. If these subjects had CGD, it would be of a hypomorphic variant that has not previously been described.

Molecular diagnosis of severe combined immunodeficiency--identification of IL2RG, JAK3, IL7R, DCLRE1C, RAG1, and RAG2 mutations in a cohort of Chinese and Southeast Asian children

Severe combined immunodeficiencies (SCID) are a group of rare inherited disorders with profound defects in T cell and B cell immunity. From 2005 to 2010, our unit performed testing for IL2RG, JAK3, IL7R, RAG1, RAG2, DCLRE1C, LIG4, AK2, and ZAP70 mutations in 42 Chinese and Southeast Asian infants with SCID adopting a candidate gene approach, based on patient's gender, immune phenotype, and inheritance pattern. Mutations were identified in 26 patients, including IL2RG (n = 19), IL7R (n = 2), JAK3 (n = 2), RAG1 (n = 1), RAG2 (n = 1), and DCLRE1C (n = 1). Among 12 patients who underwent hematopoietic stem cell transplantation, eight patients survived. Complications and morbidities during transplant period were significant, especially disseminated bacillus Calmette-Guérin disease which was often difficult to control. This is the first cohort study on SCID in the Chinese and Southeast Asian population, based on a multi-centered collaborative research network. The foremost issue is service provision for early detection, diagnosis, management, and definitive treatment for patients with SCID. National management guidelines for SCID should be established, and research into an efficient platform for genetic diagnosis is needed.

Multiple indomethacin-induced colonic perforations in an adolescent

Colonic perforation is an uncommon cause of acute abdomen in paediatric patients, and can present a diagnostic enigma as well as management challenge to the paediatric surgeon. An adolescent developed multiple colonic perforations following a short course of oral indomethacin, requiring emergency hemicolectomy. This is the youngest known case of enteral non-steroidal anti-inflammatory drug (NSAID)-mediated large bowel injury. We review current evidence on NSAID-related enteropathy, and postulate potentiating mechanisms that may have accounted for the unusually rapid clinical course of our patient.

Academy of medicine, Singapore-Ministry of Health clinical practice guidelines: management of food allergy

The Academy of Medicine, Singapore (AMS) and the Ministry of Health (MOH) publish clinical practice guidelines to provide doctors and patients in Singapore with evidence-based guidance on managing important medical conditions. This article reproduces the introduction and executive summary (with recommendations from the guidelines) from the AMS-MOH clinical practice guidelines on the Management of Food Allergy, for the information of readers of the Singapore Medical Journal. Chapters and page numbers mentioned in the reproduced extract refer to the full text of the guidelines, which are available from the Academy of Medicine website: http://www.ams.edu.sg/guidelines.asp#foodallergy. The recommendations should be used with reference to the full text of the guidelines. Following this article are multiple choice questions based on the full text of the guidelines.

The changing face of food hypersensitivity in an Asian community

BACKGROUND

Food allergy seems to be increasing in Asia as well as world-wide. Our aim was to characterize food protein sensitization patterns in a population of Asian children with possible food allergy.

METHODS

Children presenting to our allergy clinic over 3 years with symptomatic allergic disease and at least one specific food allergen sensitization documented on skin prick testing were included in the analysis.

RESULTS

Two hundred and twenty-seven patients fulfilled inclusion criteria. Ninety (40%) of the positive skin tests were positive to egg, 87 (39%) to shellfish, 62 (27.3%) to peanut, 30 (13.2%) to fish, 27 (11.8%) to cow's milk, 21 (9.3%) to sesame, 13 (3.7%) to wheat and eight (3.2%) to soy. Peanut sensitization was the third most common sensitizing allergen, and seen mostly in young atopic children with multiple food hypersensitivities and a family history of atopic dermatitis. The median reported age of first exposure to fish and shellfish was 6 and 12 months, respectively. The mean age at presentation of children with shellfish hypersensitivity was at 6.7 years of age. The likelihood of shellfish sensitization was increased in children with concomitant sensitization to cockroaches.

CONCLUSIONS

In contrast to previously reported low peanut allergy rates in Asia, in our review, peanut sensitization is present in 27% (62/227) of food-allergic children, mostly in patients with multiple food protein sensitizations. Temporal patterns of first exposure of infants to fish and shellfish are unique to the Asian diet. Shellfish are a major sensitizing food source in Asian children, especially in allergic rhinitis patients sensitized to cockroaches.

Sensitization to dust mites in children with allergic rhinitis in Singapore: does it matter if you scratch while you sneeze?

BACKGROUND

Previously published data established Blomia tropicalis, as the major source of allergic sensitization in asthmatic children in tropical Singapore. Objective To define the prevalence, clinical characteristics and risk factors of species-specific mite sensitization in paediatric allergic rhinitis (AR) patients in this unique environment.

METHODS

We performed a prospective evaluation of newly diagnosed AR patients, from 1 May 2003 to 30 April 2004, from the otolaryngology and allergy outpatient clinics of the Kendang Kerbau Children's Hospital in Singapore. Patients included in the study showed evidence of sensitization to at least one respiratory allergen source and completed a detailed questionnaire. Relative risk of sensitization and associated risk factors were calculated using logistic regression analysis with the forward stepwise model. Multivariate regression analysis was performed to adjust for confounding interactions. Continuous values were compared using anova, SPSS 9.0 for Windows (SPSS Inc., 1999).

RESULTS

One hundred and seventy-five patients were included, 119 (68%) males, 142 (81%) Chinese, age mean 7.9 years (range 2-16). Sixty-eight patients (39%) reported a concomitant diagnosis and/or clinical complaints of bronchial asthma and 84 (48%) of atopic dermatitis. Skin prick test results were positive for traditional house dust mites (Dermatophagoides pteronyssinus. and D. farinae mix) in 85% of patients and for B. tropicalis in 62%. Overall mite sensitization was 98%, household pets 10%, moulds 9% and food proteins 12%. By far the single most significant factor associated with Dermatophagoides sensitization in this group was the presence of allergic eczema (odds ratio (OR) 31.8%, 95% confidence interval (CI) 3.6-285, P=0.002). Allergic eczema was negatively associated with B. tropicalis sensitization (OR 0.26%, 95% CI 0.14-0.5).

CONCLUSIONS

Children with AR and concomitant atopic dermatitis show a preferential sensitization to the Dermatophagoides mites. In our population, B. tropicalis sensitization is more prominent in children with pure respiratory allergy.

Infective endocarditis in childhood: a seven-year experience

INTRODUCTION

The epidemiology, clinical features, treatment and outcomes of infective endocarditis (IE) are reviewed.

METHODS

A retrospective descriptive study was performed involving patients treated for IE at a paediatric tertiary centre in Singapore, between May 1997 and April 2004. Duke criteria were used to retrospectively evaluate the diagnosis of IE in these cases. Data analysis was performed using SPSS for Windows.

RESULTS

There were a total of 27 children with IE in the seven-year study period. Of these, 24 (88.9 percent) had congenital heart disease, one had rheumatic valvular heart disease and two had normal anatomy. Fever (81.5 percent) was the primary presenting symptom, while splenomegaly (40.7 percent) and septic spots (22.2 percent) were the most common physical findings. C-reactive protein was raised in all cases with a mean of 100.1mg/L. Blood cultures were positive in 77.8 percent of cases and the most common organism identified was Viridans Streptococcus species (25.9 percent). Vegetations were detected on echocardiography in 55.5 percent of cases. According to the Duke criteria, 48.1 percent of our patients fulfilled the clinical diagnosis of definite IE and 51.9 percent had possible IE. The median duration of parenteral antibiotics was 31 days. Major complications were seen in seven (25.9 percent) patients, of whom five had either left heart vegetations or a right-to-left shunt physiology.

CONCLUSION

IE is an uncommon infection in childhood and occurs primarily in patients with congenital heart disease. Rheumatic heart disease is rarely a predisposing cause in our local children. Early diagnosis of IE is challenging and depends on a high index of suspicion. Useful clues include the presence of splenomegaly, septic emboli, microscopic haematuria and high C-reactive protein level greater than 100mg/L. The Duke criteria for the diagnosis of IE are relevant locally, but if modified with an expanded list of minor criteria including the above useful clues, may increase the sensitivity of diagnosing definite IE. The presence of left-sided heart vegetations is a strong predictor of complications and must be treated aggressively.