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General Reference ⬇

Nejm 2005;352:1899; 1995;332:581

Pathophys and Cause ⬆ ⬇

Cause: Probably polygenetic; 91% of patients have positive family history; associated with HLA antigens on chromosome 6.

Pathophys:Autoimmune inflammatory disease (Nejm 2009;361:496). Cells migrate through epidermis too fast, hence is an epidermal hyperplastic condition that never becomes neoplastic. Psoriatic arthritis when involves synovium. In exfoliative stage, can lose protein and produce negative nitrogen balance. Perhaps trauma causes initial elbow/knee changes

Epidemiology ⬆ ⬇

Worst in winter, probably from dryness and lack of sunlight; 1-2% of US population, rare in US blacks

Signs and Symptoms ⬆ ⬇

Sx:

Onset usually under age 30 yr; doubt dx if onset over age 60 yr

Precipitated by stress (emotional, alcoholic binge, postinfection, drug reaction especially propranolol, chloroquine, NSAIDs, and lithium)

Arthritis quite common, often w little or no rash, asymmetric like ankylosing spondylitis

Si:Papulosquamous rash; papule with scale that, when picked,, leads to punctate bleeding (inter-rete ridge capillary); occasional pustular variant. Elbow, knee, scalp, gluteal cleft, flexor surfaces are initial distribution often; nail pitting; Koebner's phenomenon: rash appears at site of scratch or trauma 2-3 wk later

Complications ⬆ ⬇

Gout; exfoliative dermatitis (r/o mycosis fungoides if > age 45 yr); pustular exacerbation with fever, inflammation, pain, hypocalcemia/hypoparathyroidism

r/o GUTTATE PSORIASIS: small droplet-sized lesions erupt over 1 wk poststrep infection, positive throat culture and ASO titer up (Arch Derm 1992;128:39), or with perianal strep in children (Ped Derm 1990;7:97) and spontaneously resolve over 2 mo

Lab and Xray ⬆ ⬇

Lab:

Path:Skin bx shows acanthosis (increased epidermal thickness); retention of nuclei; rete ridges deeper, bigger, and some fused; interridge capillaries tortuous and close to surface and so bleed when scale picked (Auspitz sign). Feulgen stain shows mitochondria, ribosomes, and DNA in stratum corneum

Chem:Uric acid increased (due to increased cell turnover?)

Xray:Hands look like RA except no osteoporosis; whittled-down tufts like scleroderma, "pencil in cup" dip's.

Treatment ⬆

Rx:

d/c lithium and -blockers

of scalp: steroids (DermaSmooth 0.01% hs, or other fluocinolone), Oluxfoam; salicylic acid solutions, tar shampoos, mineral oil

of other areas:

  • Sunlight or other broad band UVB source, short of burn, which will cause flare
  • Steroids topically (avoid systemic po steroids, which can precipitate pustular psoriasis) for small areas, with occlusive plastic dressings; or injections, eg, dilute (1:3) triamcinolone with lidocaine; adverse effects: widespread use leads to systemic absorption and adrenal suppression; can precipitate exfoliative erythroderm; skin atrophy; rebound much more likely than with anthralin
  • Anthralin paste, 0.1%, 0.2%, or 0.4%, to rash qd for 10 min to 1 h, then removal with mineral oil, bath, and extensive hydrophilic ointment; or Z-tar emulsion (Dithranol) topically × 1 h, then shower, follow with UV; avoid groin; stains hair, skin
  • Vit D analogs: Calcipotriene (Dovonex) (Med Let 1994;36:70) ointment 0.005% bid; a vit D analog, as good as topical steroids, although tachyphylaxis potential unknown; often used w potent or superpotent topical steroid initially then taper steroid; adverse effects: hypercalcemia at high doses because it is a vit D analog; now available only combined w betamethasone (Taclonex) much more expensive.
  • Calcitriol (Vectical) ointment bid Tazarotene gel (Tazorac) (topical retinoid) (Med Let 1997;39:105) 0.05 or 0.1% qd to <20% of body surface (<40 gm/wk); for stable plaque type psoriasis; avoid in pregnancy; $2/gm

2nd-line meds, usually used w dermatologic collaboration:

  • Methotrexate 2.5-5 mg q12h × 3 doses q1week, but check current guidelines (Arch IM 1990;150:889) w 1 mg folate po qd; 10% get liver disease (Am J Med 1991;90:711); equieffective as psoralen (Nejm 2003;349:658)
  • Psoralen or methoxsalen po with UV-A (PUVA) highly effective, used tiw × 10 wk helps 85% then maintenance q1-4wk, but increases incidence of squamous cell cancer × 3 (Nejm 1984;310:1156) including male genitals unless protected (Nejm 1990;322:1093) and melanoma risk w 10-yr lag (Nejm 1997;336:1041)
  • Immune suppression (Nejm 2001;345:248, 284):
    • Monoclonal antibodies like interleukin 12/23 of CD4 and CD8 T cells, 90 mg sc q1wk × 4 helped 81% (Nejm 2007;356:580)
    • TNF antagonists like infliximab, etanercept (Enbrel) (Nejm 2008;358:241) 50 mg biw, ustekinumab (Nejm 2010;362:118), adalimumab (Humira), alefacept (Amevive) (Med Let 2003;45:31) 7.5-15 mg iv/im q1wk × 12; adv effects: chills w infusion, cost $8400/12 wk
    • Cyclosporine works, though nephrotoxic (J Am Acad Derm 1995;32:78; Nejm 1991;324:1277)
  • Acitretin (Soriatane) (Med Let 1997;39:106) 25-50 mg po qd w food; adv effects: teratogenic for 3 yr after stop, elevated LFTs can revert on rx, various anterior eye changes, all worse w alcohol, pseudotumor cerebri esp w tetracycline; $7/pillof arthritis: (Ankylosing Spondylitis) (Arch Rheum 1996;132:215)