Diagnostics and Therapy in Veterinary Dermatology. Группа авторов

perfect example of a type IV reaction. In contact allergic dermatitis, small molecules from plants or chemicals are absorbed into the skin. These molecules by themselves do not elicit a response from the immune system and are called haptens. Once these haptens attach to a host protein, this larger complex can then be recognized, processed, and presented as a complete antigen by Langerhans cells. During presentation to naïve T cells in the lymph node, the Langerhans cell releases cytokines that induce the formation of Th1 and Th17 cells. These cells then return to the skin and upon reexposure release Th1 cytokines and activate macrophages, causing the clinical signs associated with delayed hypersensitivity.

Recommended Reading

      1 Eyerich, S., Eyerich, K., Traidl‐Hoffmann, C., and Biedermann, T. (2018). Cutaneous barriers and skin immunity: differentiating a connected network. Trends Immunol. 39: 315.

      2 Marshall, J.S., Warrington, R., Watson, W., and Kim, H.L. (2018). An introduction to immunology and immunopathology. Allergy Asthma Clin. Immunol. 14 (Suppl. 2): 49.

      3 Matejuk, A. (2018). Skin immunity. Arch. Immunol. Ther. Exp. (Warsz.) 66: 45.

      4 Pasparakis, M., Haase, I., and Nestle, F.O. (2014). Mechanisms regulating skin immunity and inflammation. Nat. Rev. Immunol. 14: 289.

      5 Richmond, J.M. and Harris, J.E. (2014). Immunology and skin in health and disease. Cold Spring Harb. Perspect. Med. 4: a015339.

      6 Simoes Quaresma, J.A. (2019). Organization of the skin immune system and compartmentalized immune responses in infectious diseases. Clin. Microbiol. Rev. 32: e00034.

      7 Smith, A.R., Knaysi, G., Wilson, J.M., and Wisniewski, J.A. (2017). The skin as a route of allergen exposure: part I. Immune components and mechanisms. Curr. Allergy Asthma Rep. 17: 6.

2 How to Get the Most Out of Your Dermatologic History and Examination

       Michelle Woodward O’Gorman

       KEY POINTS

       Listen carefully and attentively to the owner.

       It is difficult to diagnose many dermatologic diseases without a good history.

       Since dermatologic histories can be long, clients should fill out a dermatology history form before their appointment.

       Examine patients’ skin in a systematic way so no area is overlooked.

       Be sure to record findings in a detailed manner.

      Like many areas of veterinary medicine, dermatology relies on the history and physical exam to form a clinical picture. If time is dedicated to these early in a case, the clinician will have an easier time selecting and interpreting diagnostics later. A practiced dermatologist will frequently have a good clinical picture formed based on history alone, even before evaluating the patient. This can prompt the clinician to ask specific questions and more carefully evaluate certain areas of the body, although care must be taken to avoid tunnel vision.

Dermatologic History

      Every dermatologic case should start with a complete evaluation of the patient’s history, which can often take longer to complete than the actual physical examination. The first part of this process should include a review of all previous medical records. Dermatologic patients frequently have extensive medical histories and often have been managed by multiple veterinarians/clinics, sometimes even at the same time. Obtaining and reviewing medical records prior to evaluating the patient are vital, but often overlooked. People’s memories are frequently incomplete or skewed, and records can provide firm information. For instance, owners may feel that their dog’s pruritus is not seasonal, but medical records may demonstrate that the patient has only required glucocorticoids during the spring and summer months for the previous three years. Medical records can also provide information about treatment successes and failures, disease progression, and previous clinical signs.

The next part of the history is gathering the client’s perception of the problem. Veterinarians only see patients for a short window of time at the appointment. Clients, however, are typically in the patient’s presence daily and will have a more complete picture of what the pet is experiencing. Begin gathering the client history prior to the appointment by providing a standard form that can be filled out and returned in advance (example in Figure 2.1). Review of this form and the medical record prior to the appointment maximizes the time in the clinic with the client and patient. The form can have a combination of closed questions (yes or no answer) and open questions where the client can formulate a response. Both question types can help to develop the complete history. The history should also be discussed with the client, as repetition can provide more detail and allow for clarification and confirmation of previous responses.

Given a complete history including both client and record information, a reasonable differential list can often be formed prior to evaluating the patient. However, the clinician should keep an open mind and not rush the physical exam. The following elements of a patient’s history should be considered, using information collected from a completed history form, discussion with the client, and the previous medical records.

      

Figure 2.1 Example of a dermatology history form for a client.

      Signalment

      Current age and age of onset can be helpful in developing differential diagnoses (e.g. congenital disorders in young animals). The patient’s breed and coat/skin color can also be important when considering predilection for certain diseases. This is especially true for more obscure diseases that might be missed if the specific breed isn’t investigated. Sex, including whether a patient is intact or neutered, can also help to prioritize differentials.

      Chief Complaint

      In order to successfully manage a case, it is important to discover the client’s primary concern and address it, even if only through discussion and explanation. Clients can become frustrated if they perceive that they aren’t being listened to or if their pet’s main problem isn’t managed. For instance, a client may present with the chief complaint that their dog is shaking its head. If the veterinarian focuses instead on the severe skin infection that is also present, and does not address the ear infection to a level that satisfies the client, they may leave frustrated and disgruntled. Frustrated clients may not follow through with therapy at home or future appointments.

      Initial Problems

      Skin disease progresses and signs can change with time, so knowing the age at onset of symptoms and the initial clinical presentation is valuable. For instance, signs of food allergy can be seen in puppies less than 4 months of age. If a 3‐year‐old dog with recurrent pruritus and dermatitis presents for evaluation, being aware that clinical signs have been present since the patient was 5 months of age may make a differential such as food hypersensitivity more likely in the veterinarian’s mind. Discussion of the evolution of clinical signs (e.g. initially just ear infections, now also paw licking and scooting on rear end) is also important, as owners may not recognize previous issues as significant.

      Clinical Signs

      Clinical signs of