Keratoderma blennorrhagicum

What is Keratoderma blennorrhagicum?

Keratoderma blennorrhagicum (KB) is a chronic, inflammatory skin disorder that presents as painful, hyperkeratotic (thickened) lesions, most often on the soles of the feet, palms, and sometimes the knees or elbows. The word comes from Greek roots: “kerato‑” (horn), “derma” (skin), and “blennorrhagicum” (referring to the blister‑like, ulcerated nature of the lesions). Although the appearance can mimic psoriasis, KB is classically linked to the systemic inflammatory disease psoriatic arthritis (PsA) or other autoimmune disorders. The lesions may be pustular, scaly, or ulcerated and can cause significant discomfort and functional limitation.

In most dermatology textbooks, KB is described as one of the “skin‑type” manifestations of Reiter’s syndrome (now called reactive arthritis) and is considered a marker of severe, systemic inflammation. Early recognition is important because it often signals active joint disease that may require aggressive treatment.

Common Causes

KB is not a disease itself but a cutaneous sign of several underlying conditions. The most frequent triggers include:

• Psoriatic arthritis (PsA): The leading cause; up to 30 % of PsA patients develop KB.
• Reactive arthritis (formerly Reiter’s syndrome): Frequently follows gastrointestinal or genitourinary infections.
• Inflammatory bowel disease (IBD): Especially ulcerative colitis and Crohn’s disease.
• Autoimmune dysregulation: Conditions such as systemic lupus erythematosus or ankylosing spondylitis can rarely present with KB‑like lesions.
• Infections: Chronic fungal (tinea pedis) or bacterial infections can precipitate secondary hyperkeratosis that mimics KB.
• Medication reactions: Certain drugs (e.g., β‑blockers, lithium, antimalarials) may trigger pustular eruptions resembling KB.
• Genetic predisposition: HLA‑B27 positivity increases risk for reactive arthritis and associated cutaneous findings.
• Trauma or pressure: Repetitive friction on the soles may exacerbate existing lesions.
• Metabolic disorders: Rarely, hyperkeratotic lesions appear in patients with dyslipidemia or diabetes where vascular insufficiency worsens skin integrity.

Associated Symptoms

Because KB usually co‑exists with systemic disease, patients often report additional signs:

• Joint pain, swelling, and stiffness—particularly in the spine, sacroiliac joints, and peripheral joints (knees, ankles, fingers).
• Enthesitis (pain at tendon insertions) such as Achilles tendon pain.
• Conjunctivitis or uveitis (eye inflammation) – classic in reactive arthritis.
• Urethritis or other genitourinary symptoms after a prior infection.
• Gastrointestinal upset (diarrhea, abdominal cramping) that may precede skin changes in reactive arthritis.
• Generalized fatigue, low‑grade fever, or weight loss when systemic inflammation is high.
• Psoriasis plaques on the scalp, elbows, or other areas that may coexist with KB.

When to See a Doctor

Prompt medical evaluation is advised if any of the following occur:

• New, painful, thickened lesions appear on the soles or palms and do not improve with over‑the‑counter moisturizers.
• Lesions become ulcerated, ooze pus, or develop a foul odor.
• Joint pain or swelling develops in tandem with the skin changes.
• Fever, chills, or systemic signs of infection arise.
• Vision changes, eye redness, or photophobia (possible uveitis).
• Difficulty walking or bearing weight due to plantar pain.
• History of recent infection (e.g., chlamydia, gastrointestinal bug) followed by skin and joint symptoms.

Diagnosis

Diagnosing KB involves a combination of clinical assessment, laboratory testing, and sometimes skin biopsy.

Clinical examination

• Visual inspection of lesions – classic “brown‑yellow, verrucous plaques with peripheral pustules.”
• Distribution pattern – symmetric involvement of soles, sometimes extending to palms, knees, or elbows.
• Joint examination – look for swelling, tenderness, reduced range of motion.

Laboratory studies

• Complete blood count (CBC) – may show leukocytosis if secondary infection is present.
• Erythrocyte sedimentation rate (ESR) and C‑reactive protein (CRP) – markers of systemic inflammation.
• HLA‑B27 typing – positive in many cases of reactive arthritis.
• Serologic tests for recent infections (Chlamydia trachomatis, Salmonella, Shigella, Yersinia).
• Rheumatoid factor (RF) and anti‑CCP – usually negative, helping to differentiate from rheumatoid arthritis.

Imaging

• Joint X‑rays or ultrasound to assess erosions or enthesitis.
• MRI may be ordered if axial spine involvement is suspected.

Skin biopsy (optional)

If the diagnosis is unclear, a 4‑mm punch biopsy is taken. Histology typically shows:

• Hyperkeratosis with parakeratosis.
• Neutrophilic microabscesses within the stratum corneum (similar to pustular psoriasis).
• Dermal infiltrate of lymphocytes and neutrophils.

These findings help differentiate KB from other palmoplantar keratodermas.

Treatment Options

Management aims to control skin lesions, reduce systemic inflammation, and preserve joint function.

Medications

• Non‑steroidal anti‑inflammatory drugs (NSAIDs): First‑line for joint pain and mild skin inflammation.
• Topical corticosteroids: Medium‑ to high‑potency (e.g., clobetasol propionate 0.05 %) applied 1–2 times daily for up to 2 weeks.
• Topical calcineurin inhibitors: Tacrolimus 0.1 % or pimecrolimus 1 % for areas where steroids are contraindicated.
• Systemic retinoids: Acitretin 25–35 mg daily can be very effective for hyperkeratotic plaques, but requires baseline liver function tests and contraception.
• Biologic disease‑modifying antirheumatic drugs (bDMARDs): TNF‑α inhibitors (etanercept, adalimumab, infliximab) or IL‑17 inhibitors (secukinumab) are the gold standard for refractory PsA with KB.
• Conventional DMARDs: Methotrexate, sulfasalazine, or leflunomide may be used when biologics are not accessible.
• Antibiotics: If a bacterial superinfection is suspected (e.g., Staphylococcus aureus), a course of oral dicloxacillin or clindamycin is appropriate.

Physical and Home Care

• Foot hygiene: Soak feet in warm water with Epsom salts for 10 minutes, then gently pat dry.
• Moisturization: Apply urea‑based creams (10‑20 %) after bathing to keep the stratum corneum soft.
• Keratolytic agents: Salicylic acid 2 % pads or glycolic acid lotions can reduce plaque thickness.
• Protective padding: Use silicone gel pads in shoes to reduce pressure on painful lesions.
• Exercise & stretching: Low‑impact activities (swimming, cycling) maintain joint mobility without stressing the soles.
• Smoking cessation & weight control: Both improve systemic inflammation and lessen mechanical stress on foot skin.

Follow‑up and Monitoring

Patients on systemic therapy should have regular labs (CBC, liver enzymes, lipid profile) and periodic dermatologic assessments to monitor efficacy and side effects.

Prevention Tips

While KB cannot always be prevented, the risk can be lowered by managing the underlying disease and taking care of the skin:

• Control psoriatic arthritis aggressively with appropriate DMARDs or biologics.
• Avoid untreated infections—promptly treat chlamydia, gastrointestinal bugs, or skin wounds.
• Maintain good foot hygiene; keep nails trimmed and avoid excessive moisture.
• Wear breathable, properly fitting shoes; change socks daily.
• Apply moisturizers after each shower to prevent dry, cracked skin that predisposes to hyperkeratosis.
• Limit alcohol and quit smoking, both of which can worsen psoriasis‑related skin disease.
• Schedule routine rheumatology and dermatology visits, especially if you have a known HLA‑B27‑positive status.

Emergency Warning Signs

Key Take‑aways

Keratoderma blennorrhagicum is a distinctive, often painful skin manifestation of systemic inflammatory diseases, most notably psoriatic arthritis and reactive arthritis. Early recognition, accurate diagnosis, and coordinated care between dermatology and rheumatology are essential to control skin lesions, protect joint health, and prevent complications. Patients should be educated about symptoms that demand prompt medical attention, and they should receive clear guidance on skin care, medication adherence, and lifestyle measures that reduce flare‑ups.