A Rare Case of Systemic AL Amyloidosis with Muscle Involvement: A Misleading Diagnosis

Figure 1

Muscle biopsy general features and the presence of amyloid substance. (a) Hematoxylin and eosin staining: the muscle cells show regular morphological characteristics with the exception of one hypercontracted cell; (b) Gomori staining: normal histological picture; (c) succinate dehydrogenase staining (SDH): the staining shows mild changes in myofibrillar texture; (d) ATPase pH 9.4: normal muscle fiber typing and distribution. Congo red staining without (e) or with polarized light (f): presence of amyloid around/inside the wall of perimysial vessels (×20); (g) Thioflavin S staining with fluorescence microscope: amyloid substance appears bright green in dark field. It completely includes the vessel wall of some perimysial arterioles (×20).

(a)

(b)

(c)

(d)

(e)

(f)

(g)