A Skin Biopsy of the Abdominal Wall Without a Rash Is Safe and Effective in the Diagnosis of Systemic Amyloidosis

The diagnosis of systemic amyloidosis is decided through histologic materials from biopsy from different organs. This is a retrospective study from the institutional database of our hospital and consisted of patients to being judged to need skin biopsy for the purpose of diagnosing systemic amyloidosis visiting dermatology between April 2005 and August 2022. A total of 30 patients underwent the skin biopsy of dermis and fatty tissue on abdominal wall without rash and a total of 36 specimens were obtained. A total of 14 of these specimens showed amyloid deposition histologically. Among the 14 specimens, amyloid immunoglobin light chain amyloidosis in 8 samples (57.1%) was the most diagnosed, the others being wild-type amyloid transthyretin amyloidosis in 5 samples (35.8%) and amyloid A amyloidosis in 1 sample (7.1%). The skin biopsy has an 87.5% (14 of 16) sensitivity and 100% (20 of 20) specificity, with 12.5% (2 of 16) false negatives and 0% (0 of 20) false positives in diagnosis of systemic amyloidosis. Skin biopsy from normal abdominal wall skin to evaluate dermis and fatty tissue is a safe, sensitive, and specific procedure to the diagnosis of systemic amyloidosis.