Description

• Acute manifestations
  • Formation of multiple, sterile, painful pustules that have an erythematous base located surrounding and under the nail(s) that coalesce to form polycyclic “lakes of pus,” which subsequently rupture and crust
• Chronic sequelae
  • Nail changes: paronychia, onychodystrophy, onycholysis, onychomadesis, and anonychia
  • Scaling of the nail bed and periungual skin
  • Sclerosis or atrophy of soft tissue adjacent and deep to nail bed
  • Osteolysis of underlying bone, particularly distal phalanges
• Distribution
  • Typically affect distal extremities, affecting 1 to 2 digits, most frequently the 1st digits of the hands; can involve all fingers and toes
  • Predilection for dorsal surfaces of hands and feet
  • Spare the central palmar/plantar regions
  • Rarely spread proximally to involve feet, ankles, hands, and forearms. Isolated proximal psoriatic plaques are rare.

Epidemiology

• Exceedingly rare: Only case studies and series are available.
• Female predominance
• Predominantly in adults but also seen in children: observed in 4.7% cases of infantile psoriasis in one series

Etiology and Pathophysiology

• Immune dysregulation: Acute-phase reactants such as IL-1 and IL-36 likely play a role in pathogenesis (1).
• In some instances, digital trauma or infection may be an inciting event.

Genetics

• Reported associations with mutations in the IL36RN gene, which codes for the IL-36 receptor antagonist and is a cause of familial generalized pustular psoriasis (1,2)
• No observed relationship with plaque psoriasis–associated alleles HLA-B13, HLA-B17, or HLA-BW37

Risk Factors

• History of psoriasis, particularly pustular variant
• Digital trauma
• Local infection
• Smoking may contribute to exacerbations.

History

• Onset, including any triggering event
• Duration of eruption, previous episodes
• Local trauma or infection
• Impairment in manual dexterity or ambulation
• Localized symptoms: pain, pruritus, arthritis
• Systemic symptoms: fever, malaise, weight loss
• History of other immune disorder such as psoriasis, arthritis, or celiac disease
• Smoking history

Physical Exam

• Examine all skin surfaces, nails, scalp, and mucous membranes.
• Examine joints, evaluating for swelling, erythema, or effusion.
• Palpate axillary, epitrochlear, and inguinal lymph nodes to assess for lymphadenopathy.
• Observe and evaluate gait and manual dexterity.
• Measure vital signs.

Differential Diagnosis

• Bacterial infection, especially staphylococcal
• Herpetic whitlow
• Cutaneous candidiasis
• Allergic contact dermatitis
• Dyshidrotic eczema
• Parakeratosis pustulosa (in children)
• Pemphigus vulgaris
• Squamous cell carcinoma, particularly in advanced disease

Diagnostic Tests & Interpretation

Initial Tests (lab, imaging)

• Aspiration of fluid from pustules. The following should be performed on fluid:
  • Gram stain smear
  • Potassium hydroxide preparation
  • In vitro culture
• Cultures are typically sterile, unless secondary infection is present.
• There are no characteristic serologic findings; however, acute systemic inflammation during flares may result in
  • Increased neutrophil count
  • Increased C-reactive protein
• X-rays of hands and feet may show acroosteolysis, especially in long-standing disease. Ankle osteolysis may also be observed and is usually unilateral.

Follow-Up Tests & Special Considerations
Additional laboratory tests may be necessary to monitor for side effects of treatment.

Diagnostic Procedures/Other
Full-thickness cutaneous punch biopsy of an active pustule may establish diagnosis and should be performed (3,4).

Test Interpretation

• Nail bed epithelium and adjacent epidermis
  • Compact hyperkeratosis with parakeratosis with or without neutrophils
  • Focal, subcorneal neutrophilic aggregates
  • Spongiform pustules of Kogoj (leukocyte aggregates between epidermal cells, associated with spongiosis)
  • Psoriasiform epidermal hyperplasia
  • Hemorrhagic foci displaying erythrocytes and hemosiderin
• Dermis
  • Superficial perivascular inflammatory infiltrate composed of lymphocytes, histiocytes, and neutrophils
  • Tortuous, dilated vessels displaying erythrocyte extravasation
  • Edema of papillary dermis

Medication

• Topicals
  • Application under occlusion enhances absorption.
  • Topical agents generally have favorable side effect profiles but may be ineffective, especially as monotherapy:
    • Vitamin D₃ analogs, such as calcipotriol: alone or combined with topical tacrolimus, betamethasone dipropionate, or oral acitretin (4)
    • Topical corticosteroids, with or without occlusion
    • May be combined with an oral antibiotic such as a tetracycline (4)
  • 5-Fluorouracil (4)
  • Tacrolimus ointment, with or without occlusion (4)
  • Anthralin (3)
• Systemics
  • Systemic medications are generally more effective than topicals, although may be more expensive and carry increased risk of adverse effects.
  • Tumor necrosis factor-α (TNF-α) inhibitors
    • Adalimumab has shown greatest effectiveness at 40 mg every 1 to 2 weeks (3,4).
    • Etanercept 20 to 50 mg twice per week (4)
    • Infliximab 5 mg/kg IV at 0, 2, and 6 weeks and then at 8-week intervals (4)
    • Ustekinumab (5)
    • Sometimes combined with oral acitretin, methotrexate, cyclosporine, or prednisone
  • Cyclosporine (4)
  • Acitretin: possible synergistic effect with topical calcipotriol (4)
  • If cultures show secondary infection, treat with appropriate antibiotics:
    • Sulfones, namely dapsone
    • Tetracyclines
  • Colchicine

Additional Therapies

• Phototherapy and photochemotherapy have been successful as monotherapies or in conjunction with medications.
• Targeted narrow-band ultraviolet B phototherapy
  • As monotherapy or in conjunction with systemic medications (4)
• Psoralen ultraviolet A
  • With selective hand bath psoralen (4)
• Low-level polarized polychromatic noncoherent light (LPPL) plus 0.1% methylprednisolone aceponate cream

Issues For Referral

If there is suspicion of psoriatic arthritis, refer to a rheumatologist.

Follow-up Recommendations

Long-term management by a dermatologist

Prognosis

• Generally persistent, chronically relapsing course
• May lead to severe disability or complications warranting hospitalization

Complications

• Association with or progression to PPP or GPP
• Psoriatic arthritis (possible association)
• Significant psychosocial impact, due to pain and resultant loss of manual dexterity
• Fever and systemic inflammatory response syndrome
• Treatment-related complications, depending on agent used

ICD-10

• L40.2 Acrodermatitis continua

ICD-9

• 696.1 Other psoriasis

SNOMED

• 200976008 Acrodermatitis continua (disorder)
• 58143000 Localized acrodermatitis continua of Hallopeau (disorder)
• 83839005 Acrodermatitis continua of Hallopeau