A 62-year-old man with type 2 diabetes mellitus, who had been on insulin therapy for the past 20 years, was found to have subcutaneous mass formation in the abdomen during a workup of worsened glycemic control. Because of suspected amyloid deposition, he was advised to avoid injections to the mass, which led to improvement of glycemic control. However, he strongly requested mass excision and was hospitalized. After evaluation using ultrasonography and computed tomography, a total mass excision was performed, and a diagnosis of insulin-derived amyloidosis was made. Comparison of the ultrasonographic and histopathological findings demonstrated that the location of the amyloid deposition nearly corresponded to the hypoechoic region. This case highlights that ultrasonography, which is a noninvasive imaging modality, can be useful for detection of insulin-derived amyloidosis.
Insulin-derived amyloidosis (IDA) has been described as a cutaneous complication occurring at insulin injection sites and is known to cause impaired absorption of insulin [
62-year-old man with diabetes mellitus was diagnosed in 1984, treated with four injections per day of insulin since 1994. Outpatient treatment at Manda Memorial Hospital was started in 2004. In May 2011 his HbA1c was 6.7% (National Glycohemoglobin Standardization Program) and stable, but subsequently his blood glucose levels gradually increased, requiring gradual increase in the insulin dosage. In December 2012, his HbA1c worsened to 8.3%, and the total daily dose of insulin was increased to 79 units (lispro 39 units and glargine 40 units). In January 2013, injection site assessment revealed palpable subcutaneous masses in the left and right subumbilical regions. An interview at this point revealed that he had noticed the presence of them since approximately half a year earlier. He was advised to rotate the injection sites, which led to frequent occurrence of hypoglycemia. Thus, the total daily dose of insulin was then reduced by 41 units to 38 units (lispro 22 units and glargine 16 units). In July 2014, his HbA1c improved to 5.8%. These masses were strongly suggested to be IDA, for which follow-up observation was initially advised. In September 2014, however, he had worsening of subcutaneous hemorrhage on the surfaces of the masses and spontaneous pain due to pressure from a trousers belt. Thus, in accordance with his strong request, in November 2014 he was admitted to this hospital for detailed examination and mass resection. Upon admission, laboratory test values showed no particular abnormalities (i.e., fasting plasma glucose 98 mg/dL, HbA1c 5.8%, fasting C-peptide immunoreactivity 1.01 ng/mL, C-reactive protein 0.03 mg/dL, glutamic acid decarboxylase antibody < 0.4 U/mL, insulin antibody < 125 U/mL, nonspecific immunoglobulin E (IgE) 79 IU/mL, and human insulin specific IgE < 0.1 UA/mL). The body mass index was 23.9 kg/m2 (body weight, 57.5 kg). Physical examination of the affected area revealed two movable, hard, subcutaneous masses, each measuring 50 mm, in the left and right subumbilical regions. The masses had smooth surfaces, partly with subcutaneous hemorrhage and tenderness (Figure
Physical examination of the affected area: two subcutaneous masses were present, each measuring 50 mm, in the left and right subumbilical regions, with minor subcutaneous hemorrhage and tenderness (indicated by broken-lined ovals).
Contrast-enhanced CT of the abdomen (equilibrium phase): in the left and right subumbilical regions, subcutaneous masses with irregular margins are observed, each measuring approximately 60 mm. The density is heterogeneous and higher than that of the surrounding adipose tissue, without contrast-enhancement effect (indicated by arrows).
Comparison of preoperative abdominal ultrasound findings (a) and Congo red-stained histopathological findings (b). The high magnification figures (×200) of Congo red staining (c) and its green birefringence (d). (a) On ultrasonography, the subcutaneous mass is shown as a somewhat heterogeneous, hypoechoic area under the dermis. (b) Congo red-stained section of the mass shows diffuse, irregular, lumpy amyloid deposition (indicated by broken-lined ovals). When the material was stained with Congo red staining (c) and seen with polarized light, we saw green birefringence (d), diagnostic of amyloid.
Total excision of the left subcutaneous mass under local anesthesia was finally decided with the consent of the patient. After ultrasonographic assessment to determine the resection margin, under local anesthesia it was completely excised along with the adjacent epidermis and subcutaneous fat layer. The histopathological picture (Congo red staining) is shown in Figure
The diagnosis of IDA is made based on clinical evidence of a palpable subcutaneous mass and histopathological evidence of amyloid deposition [
With regard to relevant cases assessed using ultrasonography, Perciun reported a patient treated with insulin for 34 years who had a hypertrophic area at a subumbilical injection site [
Written informed consent was obtained from the patient for publication of this case report and any accompanying images.
None of the authors have any potential conflicts of interest associated with this research.
All authors contributed to the management of the patient and drafting of the manuscript, and all have approved the final submission.