Papulosquamous Skin Diseases: Psoriasis Overview

Papulosquamous Skin Diseases

• Papulosquamous disorders are conditions characterized by papules and scaly plaques.

Psoriasis

• Psoriasis is a common, chronic, scaly, immune-mediated disease affecting people of all ages (approximately 2%).
• It's typically a lifelong condition with no cure, but treatments help manage symptoms.
• Genetic predisposition is a significant factor; up to 50% of patients have a positive family history.
• Environmental factors also play a role in the development of psoriasis in genetically predisposed individuals.
• The exact cause of psoriasis isn't known; however, it's believed to involve an immune reaction leading to increased epidermal cell proliferation.
• The transit time for epidermal cell maturation from the basal layer to the surface is significantly reduced in psoriatic skin (3-4 days compared to 28 days in normal skin).
• The prevalence of psoriasis in the population is estimated to be 1-2%.
• The disease typically first manifests in the late teens and 50s. Both sexes are equally affected, although in children, girls are more commonly affected than boys (HLA-Cw6).

Provocative Factors for Psoriasis

• Trauma: Psoriasis lesions often develop at sites of prior trauma or injury (e.g., scratching, the Koebner phenomenon).
• Calcium Metabolism: Abnormalities in calcium metabolism, such as hypocalcaemia, may contribute to psoriasis.
• Immunologic Abnormalities: Underlying immune system abnormalities are associated with psoriasis.
• Infections: Streptococcal infections, particularly sore throat, are often implicated in triggering psoriasis, particularly in cases of guttate psoriasis.
• Medications: Certain drugs (e.g., antimalarials, beta-blockers, and lithium) can induce psoriasis in genetically susceptible individuals.
• Climate/Environment: Psoriasis may be influenced by environmental factors such as sunlight exposure and humidity.
• Psychological Factors: Stress and emotional distress can be triggers for psoriasis outbreaks.
• Endocrine Factors: Hormonal changes, such as during pregnancy, may contribute to psoriasis exacerbations.

Clinical Features of Psoriasis

• The primary lesion in psoriasis is a well-defined, erythematous plaque covered by laminated silvery scales.
• Common affected sites include extensor surfaces of the limbs (elbows, knees), the sacral area, and the scalp.
• Psoriasis lesions are often asymptomatic, although mild itching may occur, particularly in flexural psoriasis.

Clinical Types of Psoriasis

• Chronic Plaque Psoriasis (Psoriasis Vulgaris): This is the most common type, characterized by well-defined, erythematous plaques covered by silvery scales. Often associated with nail involvement. Scraping the lesion with a glass slide produces pinpoint bleeding (Auspitz sign).
• Guttate Psoriasis: This type primarily affects children and young adults, presenting with small, rounded, raindrop-like lesions typically on the trunk. Often preceded by a streptococcal infection.
• Scalp Psoriasis: Erythematous, well-defined, scaly areas on the scalp, typically noticeable at the hairline and behind the ears. Crucial to differentiate it from seborrheic dermatitis, which has different scale characteristics.
• Flexural Psoriasis: Occurs in body folds, where scales may appear less prominent due to skin friction and moisture. Itching is common.
• Nail Psoriasis: Characterized by nail pitting, onycholysis (separation of the nail from the nail bed), and subungual hyperkeratosis (thickening of the tissue under the nail).
• Palmoplantar Psoriasis: Affects the palms and soles, typically presenting as red, dry, thickened skin with deep fissures.

Classification of Psoriatic Arthritis

• Mono- and Asymmetric Oligoarthritis: Inflammation of the interphalangeal joints (both distal and proximal) of the hands and feet is most common. Can manifest as a "sausage digit."
• Asymmetric Distal Interphalangeal Arthritis: Similar to rheumatoid arthritis, but primarily targets smaller joints, such as in the fingers.
• Spondylitis and Sacroiliitis: Axial spondylitis (inflammation of the spine) can mimic ankylosing spondylitis. Peripheral joint involvement is also possible.

Lichen Planus (LP)

• LP is a chronic inflammatory skin disease characterized by itchy, flat-topped, violaceous (purple) papules.
• It often affects the mucous membranes (appearing as lacy white patches).
• The exact cause of LP is unknown, and no specific pathogen has been identified.
• Genetic factors appear important.
• LP can be triggered by trauma (Koebner phenomenon).
• Some evidence suggests that hepatitis C virus involvement may be a contributing factor.
• Stress may also play a part in the spread of lesions.
• Certain medications (e.g., antimalarials, NSAIDs, and gold) have been associated with causing LP.
• LP frequently affects women more than men.
• While the skin form often resolves within 1-2 years, the mucous membrane form is more persistent (5+ years), and more resistant to treatment.

Clinical Features of Lichen Planus (LP)

• LP is primarily characterized by intense itching.
• Lesions are commonly found on the flexural surfaces of the wrists, forearms, legs, genitals, and mucous membranes of the cheeks and mouth.
• Characteristic lesions are violaceous, shiny, flat-topped, and polygonal.
• Close examination often reveals a lacy, reticular (net-like) pattern of whitish lines known as Wickham's striae.

Clinical Types of Lichen Planus (LP)

• Ordinary LP: The most common type.
• Hypertrophic LP: Characterized by thickened, raised lesions.
• Linear LP: Lesions arranged in lines or grooves.
• Lichen Planus Actinic: LP in sun-exposed areas.
• Follicular LP: LP affecting hair follicles.
• LP of the nails: Potential nail changes, such as pterygium and nail dystrophy.
• LP of the mucous membranes: often presenting as lacy white, painful ulcers.
• Atrophic LP: Characterized by thinning of the skin.
• Bullous LP: LP with blisters.
• Generalized LP: LP affecting a large body area.

Diagnosis and Treatment of Psoriasis

• Diagnosis typically involves a skin examination. In some conditions like nail psoriasis, a visual inspection is sufficient
• Additional tests may include scraping of the lesion (grattage test) to assess blood vessel damage.
• Several treatment options can help to manage symptoms.
• Topical treatments (eg emollients, moisturizers, keratolytics) are helpful.
• Systemic treatments are considered for more severe cases, often utilizing immune-modulatory agents and oral medications, along with phototherapy.

Diagnosis and Treatment of Lichen Planus (LP)

• Diagnosis relies on clinical examination and biopsy, often to differentiate it from similar skin conditions
• Treatment involves addressing the symptoms, with topical and oral medications as well