Amyloid purpura

Amyloid purpura is a skin condition characterized by the deposition of amyloid proteins in the skin, leading to purpuric lesions. These lesions are typically non-blanching and can vary in size, appearing anywhere on the body. Amyloid purpura is often associated with systemic conditions involving amyloidosis, where abnormal protein deposits accumulate in various organs and tissues, disrupting their normal function.

Etiology

Amyloid purpura results from the deposition of amyloid proteins in the dermal and subcutaneous vessels. Amyloidosis itself can be classified into several types, but the most common ones associated with skin manifestations, including amyloid purpura, are primary (AL) and secondary (AA) amyloidosis. In AL amyloidosis, the amyloid deposits are composed of light chains, whereas in AA amyloidosis, they are composed of serum amyloid A protein.

Clinical Presentation

Patients with amyloid purpura typically present with purpuric lesions that do not blanch upon pressure. These lesions may be accompanied by other signs of amyloidosis, such as macroglossia, fatigue, weight loss, and organ dysfunction, depending on the organs involved. The skin lesions can range from small petechiae to larger ecchymoses and may be localized or widespread.

Diagnosis

The diagnosis of amyloid purpura involves a combination of clinical evaluation, histopathological examination, and possibly imaging studies. A biopsy of the affected skin is crucial for confirming the presence of amyloid deposits. Special staining techniques, such as Congo red staining, which shows apple-green birefringence under polarized light, are used to identify amyloid. Further investigations to determine the type of amyloid and the extent of systemic involvement may include blood tests, urine tests, and imaging studies like echocardiography or MRI.

Treatment

Treatment of amyloid purpura focuses on managing the underlying amyloidosis and relieving symptoms. For primary amyloidosis, treatment options may include chemotherapy and stem cell transplantation. For secondary amyloidosis, treating the underlying inflammatory disease can help reduce amyloid protein production. Symptomatic treatments for the skin lesions may include topical corticosteroids or laser therapy, although their effectiveness can be limited.

Prognosis

The prognosis of amyloid purpura largely depends on the extent of systemic involvement and the type of amyloidosis. Early diagnosis and treatment of the underlying condition can improve outcomes, but systemic amyloidosis can be a progressive and potentially fatal condition.

See Also

• Purpura
• Amyloidosis
• Skin lesion