A pruritic rash and rippled plaques on a woman's shin - Clinical Advisor

A pruritic rash and rippled plaques on a woman’s shin

Slideshow

  • CA1017_DermClinics_Case1

A 52-year-old Hispanic woman presents with a 3-year history of a very pruritic rash over her shins bilaterally. On examination, both shins are covered in hyperpigmented papules that have coalesced to form thin, rippled plaques. The patient is very concerned about the appearance of her legs and the intense pruritus in the areas of the rash. The patient has no other medical problems and has no systemic symptoms. She has no relevant social or family history and does not take any medications.

Lichen amyloidosis (LA) is a dermatologic condition caused by abnormal amyloid deposition. LA most commonly manifests as highly pruritic lichenoid papules on the anterior tibia bilaterally. It is the most prevalent form of primary localized cutaneous amyloidosis; the other subtypes...

Submit your diagnosis to see full explanation.

Lichen amyloidosis (LA) is a dermatologic condition caused by abnormal amyloid deposition. LA most commonly manifests as highly pruritic lichenoid papules on the anterior tibia bilaterally. It is the most prevalent form of primary localized cutaneous amyloidosis; the other subtypes are macular, nodular, and familial. It is a disorder that primarily affects individuals of Asian, Middle Eastern, or Hispanic descent, and is particularly common in Chinese individuals. Typically, it occurs in older individuals in their fifth or sixth decade of life, and affects men twice as often as women. There is also an association between LA and individuals with Fitzpatrick skin types III and IV.1-3

Clinically, LA is characterized by multiple discrete, hyperkeratotic, hyperpigmented papules that can merge, giving the appearance of a rippled pattern on the patient’s skin. These individual papules can also coalesce to form infiltrated plaques over time that are difficult to treat. Although the extensor surfaces of the lower extremities are usually the primary location involved in LA, these lesions may occur less frequently on the upper extremities, back, thighs, and face. Intense pruritus is often the chief complaint; however, in a minority of cases the patient is asymptomatic.

The precise etiology of LA is still under debate; however, the largest known risk factor for its development remains frictional rubbing and chronic irritation of the skin. Factors such as race, sex, seasonal changes, autoimmunity, and genetic predisposition are also thought to play a role in the pathogenesis of the disease. Some believe that LA may be a consequence of the intense pruritus because the pruritus often precedes skin findings by years.4-6 Another competing theory suggests a relationship between Epstein-Barr virus and the development of LA, but newer studies are finding the true association between these two harder to delineate. LA has also been associated with other systemic conditions, such as Sjögren syndrome, systemic lupus erythematosus, primary biliary cirrhosis, and multiple endocrine neoplasia type 2A. 3

LA is a keratinocyte-derived cutaneous amyloidosis. The amyloid deposits, which contain primarily keratin, are thought to be necrotic basal keratinocytes that have undergone conversion to amyloids after being exposed to frictional damage.5 Histologic examination reveals eosinophilic globules in the upper dermis.5 Epidermal findings may include hyperkeratosis and acanthosis. The amyloid deposits stained with Congo red exhibit characteristic apple-green birefringence under polarized light.4

Diagnosis of LA is usually based on clinical findings of the characteristic pretibial hyperkeratotic, hyperpigmented papules. The differential diagnosis for LA includes prurigo nodularis, lichen simplex chronicus, pretibial myxedema, and hypertrophic lichen planus.2 In difficult cases, a routine skin biopsy sent for histologic examination reveals the characteristic amyloid deposits discussed above.

Few treatment options provide adequately curative or effective results. If the patient is not bothered by the LA, there is no need for treatment, because LA has no malignant potential. However, most patients desire treatment for cosmetic reasons and for relief of the intense pruritus that is usually associated with LA. The first step in treating LA often involves disrupting the itch-scratch cycle through patient education about how chronic friction precipitates development and exacerbates LA. Patients should be told to stop scratching the lesion and to reduce friction. This can be achieved by the use of potent topical or intralesional corticosteroids that reduce pruritus and improve cosmesis. Other options include topical keratolytic agents such as salicylic acid or topical calcineurin inhibitors.3 Patients may apply topical medications under occlusion for maximized results; occlusion serves to improve the efficacy of the topical medications and reduces frictional irritation. In severe cases of LA, other treatment options such as dermabrasion, light therapy, and oral medications can be used. Dermabrasion has found some utility, as it allows for re-epithelialization in the damaged areas of tissue. Use of psoralen plus ultraviolet A or ultraviolet B phototherapy was shown to have moderate effects in improving pruritus and roughness in 1 study.3 Systemic medications such as acitretin and cyclosporine have shown benefits in a small group of patients.1

The patient in this clinical vignette was diagnosed with LA and educated about the need to stop the itch-scratch cycle and reduce friction to the area. She was prescribed clobetasol ointment (a potent topical steroid) to apply twice daily under occlusion. With the use of steroids under occlusion, the pruritus subsided and her rash started to improve clinically.

Ben Varughese is a medical student at the Baylor College of Medicine, and Christopher Rizk, MD, is a dermatology resident at the Baylor College of Medicine in Houston.

References

  1. Bolognia JL, Jorizzo JL, Schaffer JV, eds. Dermatology. 3rd ed. Philadelphia, PA: Elsevier Saunders; 2012.
  2. Chen JF, Chen YF. Answer: can you identify this condition? Can Fam Physician. 2012;58(11):1234-1235.
  3. James WD, Berger TG, Elston DM, Neuhaus IM, eds. Andrews’ Diseases of the Skin: Clinical Dermatology. 12th ed. Philadelphia, PA: Elsevier; 2016.
  4. Rapini RP. Deposition and metabolic diseases. In: Rapini RP ed. Practical Dermatopathology. 2nd ed. Philadelphia, PA: Elsevier Mosby; 2012:119-137.
  5. Salim T, Shenoi SD, Balachandran C, Mehta VR. Lichen amyloidosis: a study of clinical, histopathologic and immunofluorescence findings in 30 cases. Indian J Dermatol Venereol Leprol. 2005;71(3):166.
  6. Weyers W, Weyers I, Bonczkowitz M, Diaz-Cascajo C, Schill WB. Lichen amyloidosis: a consequence of scratching. J Am Acad Dermatol. 1997;37.6:923-928.

Next hm-slideshow in Dermatology Clinics