Clinical Signs of Dermatological Disease PDF

Clinical problems in dermatology RCI I Integrated Master in Veterinary Medicine 2024-25 Ana Oliveira, MV, MsC, Dip ECVD, PhD EBVS European Specialist in Veterinary Dermatology  Dermatological signs Dermatological clinical signs are a common owner complain. The dermatological clinical signs can...

Clinical problems in dermatology RCI I Integrated Master in Veterinary Medicine 2024-25 Ana Oliveira, MV, MsC, Dip ECVD, PhD EBVS European Specialist in Veterinary Dermatology  Dermatological signs Dermatological clinical signs are a common owner complain. The dermatological clinical signs can suggest several diseases and have to be associated with the history and signalement of the patient. Papules and pustules https://www.rvc.ac.uk/review/dermatology/lesions/papules.htm Papules and pustules Papule A small, solid, raised skin lesion less than 1 cm in diameter. Papules are often associated with inflammation and can be caused by a variety of conditions such as infections and allergies. Pustule A small, circumscribed elevation of the skin that contains pus. Pustules are commonly seen in bacterial infections (e.g., pyoderma) or immune-mediated diseases (e.g., pemphigus foliaceus). https://www.rvc.ac.uk/review/dermatology/lesions/papules.htm  Crusts A secondary skin lesion that forms when dried exudate (serum, blood, or pus) accumulates on the skin surface. Crusts often result from ruptured pustules, vesicles, or erosion of the skin. https://doi.org/10.3390/ani11061662 Alopecia Alopecia The partial or complete loss of hair in areas where it is normally present. Alopecia can be due to a wide range of causes, including infections (e.g., dermatophytosis), endocrine disorders (e.g., hypothyroidism), immune-mediated diseases, or traumatic/self-inflicted damage. Credit: JodiJacobson / Getty Images  Lumps and bumps (nodules) Nodules Palpable, solid, raised lesions greater than 1 cm in diameter that extend into the deeper layers of the skin, such as the dermis or subcutaneous tissue. Nodules are often associated with neoplasia, granulomatous inflammation, or deep infections. https://www.vin.com/vetzinsight/default.aspx?pid=756&catId=-1&id=8161297  Urticaria Urticaria Also known as hives, this refers to transient, raised, erythematous, and often pruritic wheals resulting from dermal edema. Urticaria is typically associated with allergic reactions or hypersensitivity. https://www.horsejournals.com/horse-care/illness-injury/diseases/scratching-surface-equine-skin-diseases Erythema Erythema A reddening of the skin caused by increased blood flow in the superficial capillaries, often due to inflammation, irritation, or infection. Erythema is a nonspecific finding and can occur with many dermatological and systemic conditions. https://www.vettimes.co.uk/article/using-essential-fatty-acids-in-canine-atopic-dermatitis/ PRURITUS Pruritus is a common skin complaints in small animals, equine and farm animal dermatology consultations. PRURITUS Owners may not always recognise that their animal behaviour. It is therefore important to make owners aware of signs of itch other than obvious scratching, such as: Rolling Rubbing Chewing Scooting Head shaking Licking PRURITUS: rubbing https://vethelpdirect.com/vetblog/2021/08/24/6-ways-to-treat-sweet-itch-in-horses/ PRURITUS: bitting PRURITUS: dog scratching Physiology of the pruritus Pruritus is an unpleasant sensation of the skin provoking the urge to scratch or lick. The physiological rationale for pruritus is to eliminate parasites. Pruritus is an autonomous, pain-independent sensation, which is transmitted to the thalamus via itch-specific neuronal pathways. Recognition of pruritus leads to scratching, which induces pain over-riding the itch sensation. Physiology of the pruritus Physiology of the pruritus Pruriceptors are specific free nerve endings located in the skin. After stimulation, the pruritic sensation is transmitted via afferent, slow-conducting C-fibres to the dorsal horn of the spinal cord and via central itch-specific neuronal pathways to the thalamus. Physiology of the pruritus: mediators The pruriceptors are stimulated by mediators like cytokines. The cytokine IL-31 has been identified as the major pruritic cytokine in people, canines and felines, predominantly produced by TH2 cells. Physiology of the pruritus: mediators Other mediators stimulating pruriceptors are IL-2 (IL-6, IL-8 presumed) predominantly from T cells and mast cells, neuropeptides from keratinocytes, kinins, amines (including histamine), proteases (produced by, e.g. neutrophils, bacteria, fungal organism, mast cells, other inflammatory cells), prostaglandins, leukotrienes, neurophins and substance P. Physiology of the pruritus: level of pruritus Qualitative grading: mild, moderate, severe or very severe. The qualitative grading is very subjective. The use of scales provides a more accurate characterization of the level of pruritus. Physiology of the pruritus: level of pruritus There is a validated visual analogue scale of pruritus available (Hill et al, Vet Dermatol 2007 18(5):301-8) to objectify owners’ subjective perception of pruritus, and this can also be useful in monitoring the effect of treatment on the level of itch. Physiology of the pruritus: level of pruritus Physiology of the pruritus: mediators Interestingly, not every mediator induces in every species or even every dog breed itch or even the same level of itch; the specific mechanisms to explain these differences in detail are still to be elucidated.  Pruritus and chronicity Unfortunately, self-trauma subsequent to pruritus will result in release of more mediators of pruritus, and hence a vicious itch– scratch cycle is initiated, even though the original inciting cause may have resolved. Increased numbers of itch fibres will further enhance pruritus, and hyperaesthesia of the skin will develop over time. Pruritus threshold The pruritus threshold is the level after which the pruritus appears clinically. The pruritus threshold is different for between animal species, breeds and individuals. Each individual has a pruritus threshold. Pruritus threshold https://metroeasthomevetcare.com/stop-the-itch/ Pruritus threshold The itch threshold in humans has been shown to be increased in the following circumstances: At night By increased skin temperatures By decreased skin hydration With increased psychic stress. Pruritus threshold Stressful situations may potentiate pruritus through release of various opioid peptides. Competing cutaneous sensations (pain, touch, heat, cold) can magnify or reduce the sensation of pruritus. Thus, the sensation of pruritus is often increased at night, as other sensory input is low. Major causes of pruritus Many skin diseases will cause pruritus, but the major ones are: Ectoparasites Infections Allergic skin disease (flea, food, environmental hypersensitivities). Pruritus sine materia Should the skin look completely normal, but the animal is pruritic, allergic skin disease should be considered (pruritus sine materia, i.e. clinically normal with pruritus). The consequences of the pruritus Secondary lesions, such as excoriations, erythema and alopecia occur due to the self-trauma. The hair loss occurs due the trauma involved in the process of scratching, rubbing and licking. Liquenification and hyperpigmentation occurs at later stages. https://www.worldhorsewelfare.org/advice/sweet-itch Erythema and scoriations Onset of the pruritus: rapid or gradual A rapid onset of pruritus is most often associated with acute secondary superficial pyoderma, Malassezia dermatitis, ectoparasite infestation, particularly Sarcoptes, Cheyletiella or fleas or ingestion of an ingredient to which the patient is hypersensitive. In patients with environmental hypersensitivities, there is more likely a gradual increase in pruritus when entering their allergy season. Seasonality Seasonality If the pruritus recurs only in a particular season, it may suggest a likely triggering factor. For example: Flea-related pruritus is more common in the summer months. Grass hypersensitivity is more likely in spring and summer months. Perennial pruritus (pruritus during all year) Perennial itch could be related to food hypersensitivity and/or house dust/storage mite hypersensitivity. Conclusion of the class Recognize the presence of pruritus Understand the physiology and pathophysiology of the pruritus Characterize the different types of pruritus