Primary immunodeficiency diseases ‘Look deeper into nature, and then you will understand everything better.’ – Albert Einstein

Suvarna Buldeo, MB ChB, DTMH, FCPathClin, MMed (ClinPath) Clinical Pathologist, Molecular Medicine and Haematology Department, National Health Laboratory Service and Faculty of Health Sciences, University of the Witwatersrand, Johannesburg Suvarna Buldeo has a special interest in the diagnosis of immunological conditions, especially primary immunodeficiency diseases. She attended the Basic and Advanced Courses in Clinical Immunology hosted by the Federation of Clinical Immunology Societies, USA, and completed a fellowship in Clinical Immunology at the University of Utah. She hopes to use the knowledge gained to improve immunology diagnostic services in South Africa.

Melinda Suchard, BSc, MB BCh, FCPath (SA) Clin, MMed (Clin), DTM&H Clinical Pathologist, Molecular Medicine and Haematology Department, National Health Laboratory Service and Faculty of Health Sciences, University of the Witwatersrand Melinda Suchard has an interest in flow cytometry, particularly its application to infectious disease immunology and immuno-regulation. She is currently registered for a PhD, the aim of which is development of a novel method to enumerate antigen-specific T lymphocytes. Other research interests include detection of regulatory T cells and indoleamine 2,3 dioxygenase. Dr Suchard runs a diagnostic flow cytometry laboratory for kidney transplant immunology. She co-ordinates a Short Course in Basic and Advanced Immunology for clinicians and scientists at Wits and hopes to see immuno-pathology become an HPCSA-accredited medical specialty.

Monika Esser, MMed Paed (Rheum) Specialist Rheumatologist, Head, Immunology Unit, Medical Microbiology Division, National Health Laboratory Service and Faculty of Health Sciences, Stellenbosch University, Tygerberg, W Cape Monika Esser’s interests are primary immunodeficiencies and rheumatological disorders of childhood.

Correspondence to: S Buldeo ([email protected])

Primary immunodeficiency diseases (PIDs) throughout South Africa but the threshold (requiring intravenous antibiotics and are a group of disorders with defects in the for investigation among healthcare workers hospital admission), Persistent (difficult to development or function (or both) of the is high. This review aims to increase the treat with standard regimens), caused by immune system. Most PIDs originate from clinical suspicion of PIDs in South Africa Unusual infective organisms (opportunistic mutations in single genes, but polygenic and provide an approach to the diagnosis pathogens) and Recurrent (repeated forms do occur.1 The global prevalence of and management. infection at the same site or with the same PIDs varies between 0.3 and 12 per 100 000 organism). These infective features have population, and is higher in areas with high been given the acronym SPUR. PID should rates of consanguinity.2 The prevalence in Early diagnosis also be suspected in individuals with early- South Africa is unknown, but according is important as onset autoimmune diseases or malignancy.5 to prevalence data reported from the PID register,3 these diseases are either missed therapeutic options Presentation may occur soon after birth or or not reported. The possible reasons for are available to treat may be delayed, depending on the immune under-diagnosis are that patients presenting and prevent long- defect.1 Typically, T lymphocyte and with recurrent, persistent, severe or even combined defects are severe and patients unusual infections are treated without term sequelae such as present before 6 months of age. Patients investigating the underlying cause, or bronchiectasis, which with antibody deficiencies generally present the diagnosis is missed in the face of the will improve quality after 6 months of age when passive maternal overwhelming burden of similar clinical antibodies have declined, or often much presentations of infectious diseases such as of life and decrease later in life. Patients with complement and HIV and tuberculosis. mortality. phagocytic defects frequently have a delayed presentation.6 Early diagnosis is important as therapeutic options are available to treat and prevent Warning signs Major immune defects and long-term sequelae such as bronchiectasis, PID should be strongly suspected in an their associated infections1,7 which will improve quality of life and individual who has a family history of the The immune system comprises the innate decrease mortality.4 Basic laboratory disease. Warning signs are failure to thrive (complement and phagocytes) and adaptive assays to screen for PIDs are available or a history of infections that are Severe responses (T and B lymphocytes). The

278 CME August 2012 Vol. 30 No. 8 Primary immunodeficiency diseases

Table 1. Infections commonly associated with the major immune defects Immune defect Bacteria Virus Fungi Protozoa Complement Neisseria spp., - - - deficiency streptococci, Haemophilus influenzae, other encapsulated bacteria

Phagocytic defects Staphylococcus aureus, Pseudomonas - Candida spp., Aspergillus - aeruginosa, non-tuberculous spp. mycobacteria

Antibody deficiency Streptococci, staphylococci, Enteroviruses - Giardia lamblia Haemophilus influenzae, Moraxella catarrhalis, Pseudomonas aeruginosa, Mycoplasma pneumoniae

T cell defects Similar to antibody deficiencies but All viruses Candida spp., Aspergillus Pneumocystis jirovecii, also includes the intracellular bacteria spp., Cryptococcus Toxoplasma gondii, Salmonella typhi, Listeria monocytogenes neoformans, Cryptosporidium and non-tuberculous mycobacteria Histoplasma capsulatum parvum

Modified from referance 10.

Table 2. Classification of PIDs PID group Associated features Example 1. Combined immunodeficiencies Failure to clear live vaccines, Severe combined early-onset infections (Pneumocystis jirovecii, viral immunodeficiencies (SCIDs) or bacterial), persistent Candida infections 2. Well-defined syndromes with Distinct clinical features in addition to immune deficiency DiGeorge anomaly immunodeficiency 3. Predominantly antibody deficiency Decreased antibody levels with recurrent infections, especially Severe reduction in at least two sinopulmonary (encapsulated bacteria) and gastrointestinal serum immunoglobulin isotypes infections (enterovirus and Giardia) with normal or low numbers of B cells, e.g. combined variable immunodeficiency disorders (CVIDs) 4. Diseases of immune dysregulation Significant autoimmune manifestations X-linked lymphoproliferative disorders 5. Congenital defects of phagocyte Recurrent and severe bacterial, mycobacterial and fungal X-linked chronic granulomatous number, function, or both infections (respiratory, cutaneous) or deep-seated abscesses disease 6. Defects in innate immunity Recurrent bacterial, viral (in particular herpes simplex), and Chronic mucocutaneous candidiasis fungal (often Candida) infections 7. Auto-inflammatory disorders Recurrent fever, rash, urticaria Defects affecting the inflammasome, e.g. hyper-IgD syndrome 8. Complement deficiencies Recurrent Neisseria spp. infections Late complement component deficiency complement system recruits phagocytes, intracellular killing mechanisms. If phagocytes infected cell. Extracellular pathogens (e.g. most enhances phagocytosis or directly lyses cannot kill the pathogen, foreign pathogen bacteria) activate CD4+ T helper lymphocytes, bacteria. Phagocytes (neutrophils, monocytes, peptides are presented to T lymphocytes. which help B cells to produce antibody. CD4+ macrophages and dendritic cells) engulf Intracellular pathogens (e.g. viruses) activate T lymphocyte defects therefore result in a extracellular pathogens and destroy them by CD8+ cytotoxic T lymphocytes to kill the picture of both T and B cell dysfunction – a

279 CME August 2012 Vol. 30 No. 8 Primary immunodeficiency diseases

combined deficiency similar to the features • Neutropenia – may be congenital, • Quantitation of lymphocytes, which is seen in HIV infection. cyclic or occur in aplastic anaemia. the enumeration of B lymphocytes, T • Lymphopenia – suggests a T cell lymphocytes and natural killer (NK) Infections commonly associated with the disorder because approximately 70% cells by flow cytometry. Absence of B major immune defects are given in Table 1. of circulating lymphocytes are T cells. cells with normal T cells and NK cells is The type of infection can assist the clinician • Leukocytosis that persists between in keeping with agammaglobulinaemia, in recognising particular syndromes and in infections may occur in leukocyte while reduced T cells are found in severe directing the laboratory investigations. adhesion deficiency (LAD). combined immunodeficiency syndrome • Thrombocytopenia and the presence (SCID). of microthrombocytes in male infants These simple tests are usually sufficient Presentation may occur suggest Wiskott-Aldrich syndrome. to make the diagnosis of a PID and to soon after birth or may • Anaemia may suggest autoimmune commence therapy or refer the patient. be delayed, depending haemolytic anaemia, which may If the above-mentioned tests are normal, occur in common variable immune and suspicion of PID remains, functional on the immune defect. deficiency (CVID), or anaemia of assessments (step 2) should be undertaken. chronic disease. • A peripheral blood smear should Classification of PID be examined for features of asplenia The most critical The Expert Committee of the International or impaired splenic function. part of the medical Union of Immunological Societies updated Granulocytes may have morphological the classification of PIDs in 2011.8 PIDs can abnormalities (e.g. giant granules in evaluation is obtaining be classified into 8 major groups (Table 2). Chédiak-Higashi syndrome). a good history and • Absent staining of myeloid cell performing a physical Differential diagnosis6 granules shows myeloperoxidase The differential diagnosis includes causes deficiency. examination, as the of secondary immune deficiency such as • Quantitative immunoglobulins for site and types of chronic infections, malnutrition, use of immunoglobulin M (IgM), IgG, IgA infections may provide immunosuppressive drugs, splenectomy, and IgE. IgD is not routinely measured. malignancy and burns. Antibody deficiencies account for the clues about the majority of reported cases of PID. underlying defect. Diagnosis Selective IgA is the most common The most critical part of the medical PID, and the majority of these patients evaluation is obtaining a good history and are asymptomatic. IgA is absent in Step 2 performing a physical examination, as the selective IgA deficiency. Low levels • Functional analysis of B lymphocyte site and types of infections may provide of immunoglobulins with normal B and IgG subclasses. Analyse antibody clues about the underlying defect. lymphocyte numbers suggest CVID. responses to protein antigens (e.g. High IgM levels with low IgG/IgA/IgE antibody response to tetanus vaccine) Laboratory investigations and occur in class switch recombination and polysaccharide antigens (e.g. their clinical significance deficiencies. High IgE levels are antibody response to Streptococcus A stepwise approach should be employed characteristic of the hyper IgE syndrome pneumoniae polysaccharide vaccine). when investigating a patient for a possible but also found in Omenn syndrome, If the antibody response to a vaccine PID.7 which is a combined immune deficiency. antigen is low, the patient should Step 1 • Complement levels are evaluated by be vaccinated to ensure appropriate • Exclude causes for secondary immune the CH50 and AH50 – screening tests exposure, and antibody levels should defects, e.g. HIV or Mycobacterium that assess the ability of the classic be retested 4 weeks after vaccination. tuberculosis infection, or do a sweat test and alternative complement pathways IgG subclasses should only be requested to exclude cystic fibrosis. respectively to haemolyse red blood cells. if total IgG is normal, if IgA is absent, • Full blood and differential count with Reduced haemolytic activity is noted in hyper IgE syndrome is suspected or peripheral smear: This is used to assess complement factor deficiencies, but also antibody responses to vaccines are poor. the white cell counts and to identify during infections or immune complex • Functional analysis of T lymphocytes. T specific morphological features. The diseases. Alternatively, complement lymphocyte function can be measured following features may be relevant to PID: factors can be directly measured. by analysing cytokine production

280 CME August 2012 Vol. 30 No. 8 Primary immunodeficiency diseases

or proliferation. The Mantoux test count may be used to screen for severe mumps, rubella, varicella or rotavirus, is an in vivo delayed hypersensitivity combined immunodeficiency. While in any patient with T cell or severe response to purified peptide derivative. routine screening is not practised in South immunodeficiency to prevent vaccine- T lymphocytes proliferate in response Africa, it should be essential for any child associated infections. Live vaccines to antigens and mitogens. Tests for born to a mother who has previously lost should be avoided whenever there is a function require viable cells and must an infant owing to an infectious cause. family history of severe PID. reach the laboratory within 6 - 12 hours. Neonatal screening for T lymphopenia by • Do a chest X-ray to exclude the presence • Functional analysis of the innate molecular methods from dried blood spots of chronic lung disease. immune system, including phagocytic is available in some areas of the USA.9 • Notify patients on the South African PID defects. Chemotaxis (ability of register. neutrophils to migrate to the site of General principles of • Refer the patient for specific treatment. infection), phagocytosis (engulfment of management1 The laboratory can assist with referral foreign pathogens), and the oxidative Supportive details. burst (intracellular killing) functions • Prevent infections with prophylactic of neutrophils and monocytes can be antibiotics and/or antifungals. The choice of Specific assessed. antimicrobial will depend on the immune • B lymphocyte and antibody deficiencies: defect. Penicillin is commonly used for Lifelong intravenous or subcutaneous Step 3 late complement factor deficiencies, co- immunoglobulin supplementation. Molecular tests are performed to confirm trimoxazole and itraconazole for chronic • SCID: Haematopoietic stem cell the diagnosis of specific defects. This will granulomatous disease and co-trimoxazole transplant from an HLA identical be guided by results of tests performed in for T cell defects. sibling. Gene therapy has been shown to steps 1 and 2. For example, identification of • Treat infections promptly and aggressively. be successful, as immune reconstitution a mutation in Bruton’s tyrosine kinase gene Antibiotics should be prescribed in was achieved in children with SCID. is used to confirm the diagnosis of X-linked accordance with microbiological culture However, it is not yet routinely used agammaglobulinaemia. and drug sensitivity testing. as a therapeutic modality as it caused • Give nutritional support, as micro lymphoma in some recipients. Neonatal screening for severe nutrients such as zinc, vitamin D and • Phagocytic defects: Interferon gamma primary immunodeficiency vitamin A are required for immune supplementation. Severe combined immunodeficiency is a function. medical emergency requiring urgent bone • Use only irradiated blood products for marrow transplantation and avoidance of transfusions to prevent possible graft live vaccines, such as the oral polio and versus host disease. bacille Calmette-Guérin (BCG), routinely • Avoid the use of live attenuated given at birth. The total lymphocyte vaccines, e.g. oral polio, BCG, measles,

In a nutshell • PIDs are caused by genetic defects in the immune system. • Suspect PID in any individual with SPUR (Severe, Persistent, Unusual and Recurrent infec- tions). • PIDs cause severe morbidity and irreversible infection-related pathology, which can be pre- vented by early diagnosis. • Simple screening assays to assist with diagnosis are available. Screening tests include a full blood count and differential, enumeration of B, T and natural killer (NK) cells, quantitation of immunoglobulins and measurement of complement components. • Laboratory work-up should be guided by the history and examination. • Appropriate therapeutic options to treat, prevent organ pathology and improve quality of life are available. • Antibody deficiencies are the most common PIDs and are easily treated with immuno- globulin supplementation. • Avoid live vaccines in patients with severe PIDs. • Treat infections aggressively and use prophylactic antimicrobials to prevent new infections.

Acknowledgement: Manuscript writing course supported by the NIAID P30-A150410 University of North Carolina Center for AIDS Research.

Carvetrend Island CME May2011.indd 1 5/12/11 9:13 AM

281 CME August 2012 Vol. 30 No. 8