Psoriasis

Chronic immune-mediated inflammatory skin condition driven by T-cell (Th17) activation, causing keratinocyte hyperproliferation.

Genetic predisposition with environmental triggers (streptococcal infection, trauma/Koebner phenomenon, stress, alcohol, smoking, certain drugs: lithium, beta-blockers, antimalarials, abrupt steroid withdrawal).

Classified: plaque psoriasis (most common, ~80-90%), guttate (post-streptococcal, small droplet lesions, often children/young adults), flexural/inverse (skin folds, minimal scale), pustular (localized or generalized: von Zumbusch, can be life-threatening), erythrodermic (>90% BSA, systemic illness risk: emergency).

Well-demarcated, erythematous plaques with silvery scale, symmetric distribution: extensor surfaces (elbows, knees), scalp, lower back classically.

Nail changes: pitting, onycholysis, oil-drop sign, subungual hyperkeratosis. Auspitz sign: pinpoint bleeding on scale removal. Koebner phenomenon: lesions at sites of trauma.

Psoriatic arthritis: ~20-30% of patients: asymmetric oligoarthritis, dactylitis ("sausage digit"), enthesitis, axial involvement, DIP joint involvement (distinguishes from RA).

Significant psychosocial impact, associated metabolic syndrome/cardiovascular risk.

Clinical, based on characteristic morphology/distribution. Skin biopsy: rarely needed, reserved for atypical presentation. Screen for psoriatic arthritis at each review (joint symptoms, dactylitis, enthesitis).

Consider metabolic screening (lipids, glucose, BP) given cardiovascular risk association.

Differentials: eczema, tinea corporis, seborrheic dermatitis, lichen planus, cutaneous T-cell lymphoma (mycosis fungoides: consider if atypical/refractory), pityriasis rosea (guttate mimicker).

Severity assessed by BSA and impact (PASI, DLQI).

Mild-moderate (localized):

Topical corticosteroid + vitamin D analog (calcipotriol) combination: first-line, often once-daily combined product; potent steroid initially, step down
Topical vitamin D analog alone: maintenance
Topical tacrolimus/pimecrolimus: for face/flexural (steroid-sparing sites)
Coal tar preparations, salicylic acid: adjunct for scale removal
Scalp: tar/salicylic acid shampoo, potent topical steroid scalp application

Moderate-severe (extensive/refractory/significant impact/psoriatic arthritis):

Phototherapy: narrowband UVB: effective, specialist setting
Systemic conventional agents: methotrexate 7.5-25mg weekly + folic acid (first-line systemic, also treats PsA), ciclosporin (rapid but not for long-term use: renal/BP monitoring), acitretin (particularly pustular/palmoplantar)
Biologics (failure of ≥2 conventional systemic therapies or contraindication, per most guidelines): anti-TNF (adalimumab, etanercept, infliximab), anti-IL17 (secukinumab, ixekizumab: highly effective for skin clearance), anti-IL23 (guselkumab, risankizumab), anti-IL12/23 (ustekinumab)
Pre-biologic screening: TB, hepatitis B/C as per RA entry

Pustular/erythrodermic psoriasis: EMERGENCY-level care: hospitalization, fluid/electrolyte/temperature monitoring, urgent dermatology, avoid abrupt systemic steroid withdrawal (can trigger)

Guttate: often self-limiting, UVB phototherapy if extensive; treat underlying streptococcal infection if active

Lifestyle: smoking cessation, alcohol moderation, weight management, cardiovascular risk factor management, psychological support/counseling for quality of life impact

Referral: dermatology for moderate-severe disease, phototherapy/systemic therapy candidacy; rheumatology for psoriatic arthritis.

Clinical toolsCalculators

BMI GCS EDD Parkland Formula

Corrected Sodium Corrected Calcium Anion Gap Creatinine Clearance Insulin Calculations qSOFA Wells PE Wells DVT CHA₂DS₂-VASc HAS-BLED CURB-65 Centor/McIsaac

Chlamydia

Also known as: Chlamydial Genitourinary Infection

Chlamydia trachomatis (serovars D through K for genitourinary disease) is an obligate intracellular bacterium and the most commonly diagnosed bacterial STI in most high income settings.

It disproportionately affects those under 25, and untreated infection in women carries significant risk of ascending infection and subsequent tubal factor infertility.

The majority of infections, particularly in women, are asymptomatic, which underlies the importance of opportunistic and targeted screening programs.

When symptomatic: in women, mucopurulent cervical discharge, postcoital or intermenstrual bleeding, and dysuria (see Cervicitis entry); in men, urethral discharge and dysuria.

Untreated infection can ascend to cause pelvic inflammatory disease in women (see that entry) and epididymo-orchitis in men.

Rectal and pharyngeal infection are frequently asymptomatic and require site-specific testing based on sexual history.

Reactive arthritis (formerly Reiter syndrome) is a recognized post-infectious complication.

NAAT testing is the diagnostic method of choice given superior sensitivity, from a first-void urine sample (men), vulvovaginal swab (self-taken or clinician-taken, equally sensitive to endocervical swab in women), or site-specific rectal/pharyngeal swab based on sexual history
Opportunistic screening is recommended for sexually active individuals under 25 in many national programs, and for anyone with a new partner, multiple partners, or symptoms suggestive of infection
Co-testing for gonorrhea, syphilis, and HIV should be offered given shared transmission routes

Doxycycline 100 mg PO bd for 7 days is now first line for uncomplicated urogenital, rectal, and pharyngeal infection, having superseded single-dose azithromycin as first choice given superior efficacy, particularly for rectal infection where azithromycin cure rates are notably lower
Azithromycin 1 g PO single dose, followed by 500 mg PO od for 2 further days (total 2 g over 3 days) is an alternative where doxycycline is contraindicated or adherence to a 7 day course is a significant concern
In pregnancy: doxycycline is contraindicated; azithromycin 1 g PO single dose (then 500 mg od for 2 days per some protocols) is first line, with amoxicillin 500 mg PO tds for 7 days as an alternative
Test of cure is not routinely required except in pregnancy, rectal infection treated with azithromycin, or where symptoms persist, given in these situations delayed clearance or treatment failure is more likely; if performed, should be delayed at least 5 weeks post-treatment to avoid false positives from residual non-viable organism DNA
Sexual partners in the preceding 6 months (or the most recent partner if longer than 6 months since last intercourse) should be tested and treated, with abstinence advised until both partners have completed treatment and, ideally, 7 days have passed
Neonatal exposure: chlamydia acquired during vaginal delivery from an infected mother can cause neonatal conjunctivitis (typically day 5 to 14) or pneumonia (typically 4 to 12 weeks); treated with erythromycin per neonatal dosing, not topical treatment alone

Referral: sexual health services for partner notification and full STI screening; gynecology if complications (PID, tubal factor infertility) develop.

Psoriasis

Overview

Clinical Features

Diagnosis

Management

Overview

Clinical Features

Diagnosis

Management