Patrick F K Yong

King's College London, London, ENG, United Kingdom

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Publications (14)109.76 Total impact

  • The Journal of allergy and clinical immunology 06/2012; 130(2):553-4; author reply 554. · 12.05 Impact Factor
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    ABSTRACT: We describe a family with the rare mutation R11X that leads to a truncated CD40 ligand (CD40L) missing the intracellular domain. The index case had detectable CD40L expression and presented at the age of 41 years with cerebral toxoplasmosis. A brother and two nephews were also identified as having the same mutation but exhibited milder and variable phenotypes. The older affected nephew had a moderately depressed immunoglobulin G level and a history of pneumonia at 4 months of age. The younger nephew suffered from sinusitis with normal immunoglobulin levels. Both nephews had absent antibody responses to a protein antigen with conserved responses to polysaccharide antigens. The two sisters of the index case are carriers who had elevated levels of IgM but remain well. This mutation may affect CD40 ligand function by reducing cell surface levels, diminishing CD40 interaction or disrupting CD40L intracellular signalling in T cells. The variable phenotype in members of this family offers an opportunity to further understand the CD40-CD40L signalling pathway in human immune responses.
    Journal of Clinical Immunology 02/2012; 32(1):70-7. · 3.38 Impact Factor
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    ABSTRACT: Common variable immune deficiency (CVID) is the commonest symptomatic primary immunodeficiency and represents a heterogenous collection of disorders resulting mostly in antibody deficiency and recurrent infections. However, autoimmunity, granulomatous inflammation and malignancy frequently occur as part of the syndrome. The etiology of the condition has been poorly understood although in recent years, significant progress has been made in elucidating genetic mechanisms that can result in a CVID phenotype. In parallel to this, advances in treatment of the condition have also resulted in improved survival and quality of life for patients. There still remains significant work to be done in improving our understanding of the disease. In addition, recognition of the condition remains poor with significant diagnostic delays and avoidable morbidity. In this article, we review CVID with a particular focus on the areas of improving diagnosis and classification, recent developments in understanding the underlying etiology and genetics; and current treatment and monitoring recommendations for patients.
    Advances in Immunology 01/2011; 111:47-107. · 7.26 Impact Factor
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    ABSTRACT: A history of anaphylaxis after transfusion of immunoglobulin A (IgA)-containing blood products in selective IgA-deficient (sIgAD) patients can be a major problem, particularly in emergencies, when large quantities of blood products are required. A 19-year-old woman with end-stage Type 2 autoimmune hepatitis required liver transplantation as her only remaining treatment option. However, she also had sIgAD, anti-IgA antibodies, and episodes of anaphylaxis after receiving IgA-containing blood products. Liver transplantation would have been extremely challenging due to the difficulty of obtaining sufficient blood products from suitable IgA-deficient donors. Hence, it became imperative to devise a protocol to desensitize her to IgA-containing blood products. Using a continuous infusion of an IgA-enriched (6 mg/mL IgA) immunoglobulin preparation with gradual increases in concentration, she was successfully desensitized to IgA. Consequently, she was able to receive standard platelets, fresh-frozen plasma, and red blood cells with no complications. This approach could prove very useful in similar cases that may require administration of large quantities of blood products particularly in emergency lifesaving circumstances.
    Transfusion 04/2010; 50(9):1897-901. · 3.53 Impact Factor
  • Patrick F K Yong, Ulrich Salzer, Bodo Grimbacher
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    ABSTRACT: The identification of mutations in the inducible costimulator (ICOS) gene in nine patients with common variable immunodeficiency (CVID) was a major breakthrough. CVID is a complex, highly heterogeneous primary immunodeficiency disease, and the discovery of these mutations revealed a molecular basis. ICOS belongs to the CD28 family of costimulatory molecules and is expressed exclusively on activated T cells. It has at least three critical functions: germinal center formation, isotype class switching, and the development of memory B cells. The discovery of human ICOS deficiency showed that a monogenic disorder could account for the full spectrum of manifestations seen in childhood and adulthood-onset CVID, including autoimmune, inflammatory, and malignant disease complications, as well as recurrent infections. Moreover, this discovery showed that a disorder which had previously been perceived as a B-cell disease might in fact have its genetic origin in human T cells. In this article, we review the role of ICOS in the mammalian immune system and human disease, as well as the discovery and characteristics of patients with ICOS deficiency. Finally, we also discuss how these 'human knockouts' have contributed to our understanding of ICOS functions and have suggested potential avenues for using therapeutic ICOS manipulation to treat other diseases.
    Immunological Reviews 06/2009; 229(1):101-13. · 12.16 Impact Factor
  • New England Journal of Medicine 04/2009; 360(10):1045-7. · 51.66 Impact Factor
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    ABSTRACT: Cerebral toxoplasmosis can occur outside the setting of advanced HIV immunodeficiency or drug-induced immunosuppression. A case of cerebral toxoplasmosis is reported in a previously healthy 41-year-old man who was found to have a genetic defect in CD40 ligand, resulting in the X linked hyper-IgM syndrome despite normal surface protein expression on flow cytometry. This highlights the fact that primary immunodeficiencies can first present late in life with a relatively mild phenotype and should be considered in the differential diagnosis of opportunistic infections in non-HIV infected patients; in addition, normal protein expression does not necessarily rule out hypomorphic mutations.
    Journal of clinical pathology 12/2008; 61(11):1220-2. · 2.43 Impact Factor
  • Patrick F K Yong, Ronnie Chee, Bodo Grimbacher
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    ABSTRACT: This article reviews the primary immunodeficiencies that result in hypogammaglobulinemia or predominantly antibody deficiency disorders. This group makes up the largest proportion of patients with primary immunodeficiency. Significant advances have been made in understanding the molecular basis and clinical characteristics of patients with the more severe forms of antibody deficiency in the last 6 years. Recognition of these disorders remains poor with significant diagnostic delay. The milder forms of antibody deficiency disorders, especially those with normal total serum immunoglobulin G levels, remain poorly characterized and understood. Further work remains to be done in understanding and recognizing these syndromes to benefit patient care and foster further knowledge of the immune system.
    Immunology and Allergy Clinics of North America 12/2008; 28(4):691-713, vii. · 2.38 Impact Factor
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    ABSTRACT: Common variable immunodeficiency (CVID) represents a heterogeneous group of primary antibody deficiency disorders characterized by recurrent infection and by inflammatory, granulomatous, and autoimmune complications. Recently, there have been significant advances in understanding the pathogenesis of the disease, with five genetic mutations identified in patients who have a CVID phenotype. Clinical care also has progressed with refinements in treatment and the development of classification schemes for prognostic and research purposes. Significant delays in diagnosis remain, however. It is likely that more genetic defects will be identified in the future, further shrinking the pool of patients who have CVID of unknown cause.
    Immunology and Allergy Clinics of North America 06/2008; 28(2):367-86, ix-x. · 2.38 Impact Factor
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    ABSTRACT: Myeloid and plasmacytoid dendritic cells (MDCs, PDCs) play critical roles in B cell development and antibody production. Primary antibody deficiencies in humans might therefore reflect a deficit in MDCs and/or PDCs. We tested this hypothesis by measuring dendritic cell (DC) subset numbers in patients with common variable immunodeficiency (CVID), X-linked agammaglobulinaemia (XLA) and specific polysaccharide antibody deficiency (SPAD). In CVID both MDC and PDC numbers were markedly reduced. There was a graded reduction in all DC subsets across the Freiburg CVID groups (memory B cell classification) and the greatest deficit was seen in group Ia cases with the most severe disease. In contrast, MDC numbers alone were reduced in XLA whilst in SPAD the DC numbers were normal. In CVID, the number of MDCs correlated strongly with switched memory B cell percentage and total B cell count. Low numbers of DCs correlated with a greater incidence of autoimmunity, splenomegaly and granulomatous disease, and a higher incidence of clinical complications. Measurement of MDC and PDC numbers provides both prognostic information for clinical management and classification of CVID cases for future pathogenetic research. Our findings are consistent with the hypothesis that deficits in DC subsets are a critical feature in CVID.
    Clinical Immunology 05/2008; 127(1):34-42. · 3.77 Impact Factor
  • Journal of investigational allergology & clinical immunology: official organ of the International Association of Asthmology (INTERASMA) and Sociedad Latinoamericana de Alergia e InmunologĂ­a 02/2008; 18(6):482-3. · 1.89 Impact Factor
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    Journal of Clinical Pathology 11/2007; 60(10):1162-4. · 2.44 Impact Factor
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    ABSTRACT: Anaphylaxis, acute coronary syndrome and pulmonary embolism are conditions commonly seen in the acute medical setting which can be difficult to diagnose. Delay in establishing the correct diagnosis can result in either delayed or inappropriate treatment, and subsequent morbidity and mortality. The cases we present highlight the necessity of good clinical assessment when evaluating such patients.
    Southern Medical Journal 03/2007; 100(3):295-7. · 0.92 Impact Factor
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    Bone Marrow Transplantation 06/2006; 37(10):983-4. · 3.54 Impact Factor