Persistent diarrhea with petechial rash - unusual pattern of light chain amyloidosis deposition on skin and gastrointestinal biopsies: A case report

Figure 3 Histopathology of abdominal fat pad biopsy. A: H&E stain at 4 × of skin biopsy with eosinophilic deposits in the upper papillary dermis and periadnexal dermis; B: Periodic Acid-Schiff stain at 10 × shows the deposition to be negative for lipoid proteinosis; C: Cytokeratin 5/6 immunostain at 10 × is blush positive but interpreted as negative, an important stain considering differential includes primary cutaneous amyloidosis of macular or lichen subtype; D: Congo red stain at 4 × under polarization showing apple green birefringence, rarely seen in cutaneous amyloidosis but always present in amyloid light amyloidosis.