Clinical immunology and allergy explores defects of the immune system. It combines both clinical and laboratory principles in the context of clinical medicine. You will have exposure to a vast array of interesting and complex medical conditions, some of which you may have heard of, some which you did not even know existed! This discipline truly combines basic sciences with clinical medicine, making the field both exciting and challenging. Cases seen can vary from simple food allergies to rare inherited diseases. Often diagnostic workup is complex, and the laboratory aspect introduces you to novel diagnostic approaches and procedures. In view of this, both management and treatment approach can be innovative and complex.
The majority of immunology-based diagnoses can be multifaceted and difficult to diagnose. Patients can present with a constellation of symptoms which require good history taking, careful clinical consideration, and specialist diagnostic work (see Table 19.1). Reasons for referral can include recurrent infections despite multiple and frequent antibiotic usage, syndromic features, recurrent swellings and rashes, and symptoms which do not seem to fit other diagnoses. Cases may overlap with other specialities including dermatology, haematology, and respiratory medicine to name a few, which makes it an interesting platform for MDT-based management.
Table 19.1 Examples of patients seen in clinical immunology
| Type of cases | Examples of diseases seen |
| Primary immunodeficiency |
• X-linked agammaglobulinaemia |
| Secondary immunodeficiency | Secondary to: |
| Allergy |
The majority of clinical work is outpatient based under allergy and immunodeficiency. Referrals can be GP sourced, or from other specialities seeking a secondary opinion on complicated cases. The increase in cases of patients with secondary immunodeficiency across disciplines has seen the emergence of combined clinics with other specialities to deliver optimum care. Although inpatient lead care is seldom found, advice with regard to management of patients with primary immunodeficiency, anaphylaxis, immunoglobulin therapy, and allergy testing is common. There may be a day unit offering immunoglobulin infusions.
(See 
‘Pathology: in the pathology laboratory’ pp. 563–564.) The laboratory aspect of immunology and allergy training is just as significant as the clinical aspect. Clinicians are taught about the principles of laboratory organization and management, through dedicated laboratory time during training. Clinicians are expected to learn about:
• laboratory organization and management
• laboratory quality management
• principles of immunoassays including assays such as immunofluorescence and flow cytometry
• analytical techniques and instrumentation
• interpretation of specific immunology assays.
The majority of procedures fall under the remit of allergy medicine. Procedures include the following:
• Skin prick testing: to multiple allergens—performed in allergy clinics.
• Challenge testing: this can be skin prick, intradermal, or oral challenges to a wide variety of allergens including (mainly) drug and food-related allergies.
• Inpatient desensitization: e.g. to antibiotics in complicated CF cases.
• Immunotherapy: delivering small quantities of allergen to patients to invoke desensitization—often outpatient based.
It is likely that the majority of questions based on immunology will be under the pathology section or integrated within exams of other specialities. You may be asked about laboratory investigations, serology, clinical features, and diagnostic testing. It is unlikely that you will see patients with primary immunodeficiency in the practical exams but it is important to consider some of the conditions as important differential diagnoses, e.g.: hereditary angio-oedema in the context of recurrent swelling and anaphylaxis. Exam questions could be MCQs, an essay, photos, and a viva.