CLINICAL HISTORY:

Signs and symptoms:  She complained of pruritic, progressively worsening dark spots on the bilateral anterior lower legs.

Previous Treatment:  She used a bleaching cream on the areas 8 years prior without improvement.

Other information:  The patient has insulin resistance, hypertension and arthritis.

PHYSICAL EXAM:

There are hyperpigmented, keratotic plaques on the bilateral anterior lower extremities.

LABORATORY TESTS:

None

DERMATOHISTOPATHOLOGY:

Punch biopsy showed a hyperkeratotic epidermis overlying papillary dermal deposits of homogenous material.

DIFFERENTIAL DIAGNOSIS:

1.   Acquired Ichthyosis
2.   Lichen Aureus
3.   Lichen Simplex Chronicus
4.   Keratosis Pilaris
5.   Scleroderma

SCROLL DOWN FOR ANSWER AND DISCUSSION.

CORRECT DIAGNOSIS:

Lichen Amyloidosis

DISCUSSION:

Lichen amyloidosis is the most common form of primary cutaneous amyloidosis. Lichen amyloidosis presents as intensely pruritic, red-brown hyperkeratotic papules most commonly seen on the pretibial surfaces. Usually it presents as unilateral lesions with eventual symmetrical distribution. Friction or chronic rubbing of the skin contributes to the cutaneous findings. Asian, Hispanic, or Middle Eastern individuals appear to be predisposed to this condition. Lichen amyloidosis is more common in men and persons aged 50-60 years old.

There are three primary forms of cutaneous amyloidosis: lichen amyloidosis, macular amyloidosis and nodular amyloidosis. Dermatologists are more likely to encounter the cutaneous forms of amyloid, which have a benign course, and less frequently the systemic form of amyloid, which has fewer cutaneous findings. Systemic amyloidosis results from amyloid protein deposition in organ systems and is associated with significant morbidity and a high mortality rate.

Histopathologically, amyloid deposits are found in the papillary dermis, usually at the tips of the dermal papillae. Amyloid appears as an amorphorous, eosinophilic, fissured substance. Lichen amyloidosis is distinguished from other cutaneous forms by the presence of marked epidermal changes including hyperkeratosis and acanthosis. Several stains demonstrate the presence of amyloid deposits in the skin. The best-known stain is Congo red, which under polarizing light demonstrates apple-green birefringence. Other stains include periodic acid-Schiff (PAS), methyl violet, crystal violet, various cotton dyes (eg, pagoda red, Sirius red) and the fluorescent dyes, thioflavin-T and Phorwhite BBU.

TREATMENT:

The patient was treated with 30% topical urea to the affected areas once daily, which greatly reduced the thickness of the lesions and decreased pruritus.

REFERENCES:

1. Wang WJ. Clinical features of cutaneous amyloidoses. Clin Dermatology. 1990;8:13-19.
2. Weyers W. et al. Lichen amyloidosus: a consequence of scratching. JAAD December 1997. 37 (6): 923-928.
3. Touart DM, Sau P. Cutaneous deposition diseases. Part I. JAAD. Aug 1998;39(2 Pt 1):149-71.
4. Lambert WC. Cutaneous deposition disorders. In: Farmer ER, Hood AF, eds. Pathology of the Skin. Vol 432. Norwalk, Conn: Appleton & Lange; 1990:50.

Additional Comment:

Since chronic rubbing seems to be the inciting factor in the deposition of amyloid in lichen amyloidosis, treatment requires identification of the underlying cause of the pruritus, habit or neuropathy. Treatment modalities include oral sedating antihistamines, topical menthol, topical and intralesional steroids, urea agents, and narrow-band UVB phototherapy. Surgical strategies including microdermabrasion and laser ablation have been used, however, the pruritus and lesions themselves have been reported to recur after these treatments.

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