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Archive: February 2021

Fibrous Body

Fibrous Body, neuro path, arkana laboratories, Muscle biopsy
A 75-year-old female patient presents with proximal muscle weakness, characteristic skin rash, and dysphagia. Laboratory workup reveals elevated CPK 3500. A skeletal muscle biopsy is performed from the right thigh and shows findings diagnostic of dermatomyositis.  The muscle biopsy also shows rare vacuolated muscle fibers with Modified Gomori Trichrome stain.  Electron microscopy is pursued.  What is the ultrastructural finding seen in the electron photomicrograph shown below?   Answer: The electron photomicrograph shows a Fibrous (filamentous) body, which is a nonspecific finding that may be seen in a variety of clinical settings, including inflammatory myopathies, such as dermatomyositis, as well as...

Diagnose This (February 22, 2021)

amyloidosis, Amyloid Spicules on Jones Silver Stain, amyloid spicules with eyelashes, renal pathology
What is your leading diagnosis when seeing this finding along the glomerular capillary loops?     ​ ​   ​   ​ ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​   ​ ​   ​ ​   ​ ​   ​...

Congophilic Inclusions

congophilic inclusions, sporadic Inclusion Body Myositis, neuropathology, arkana laboratories, neuro notes
A 68-year-old man presents with insidiously progressive proximal left thigh weakness with atrophy, left foot drop, and right hand grip strength weakness.  Laboratory work-up reveals elevated CPK 850 and negative myositis panel.  A muscle biopsy of the left thigh is performed, and shows a polymyositis-type injury pattern with myofibers containing rare rimmed vacuoles.  Using the movie below, what characteristic finding is seen with Congo red stain in this case? Answer: The images show different modalities examining a Congo red special histochemical stain demonstrating characteristic congophilic inclusions of sporadic Inclusion Body Myositis (sIBM). With a Congo red stain, the skein-like inclusions...

Renaut Body

Renaut body, neuro notes, muscle biopsy, neuropathology
Figure 1: Cross section of sural nerve with Renaut Body (arrow) and background moderate diffuse axonopathic process.  Plastic embedded thick section stained with Toluidine blue, original magnification x400. A 65-year-old female presents with complaint of numbness and tingling in her hands and feet with gradual progressive onset. She is diabetic, and clinical work-up shows no positive autoantibodies. Nerve conduction studies show electrodiagnostic findings of a mixed sensory and motor polyneuropathy.  The clinical differential diagnosis includes diabetic polyneuropathy versus chronic inflammatory demyelinating polyradiculoneuropathy (CIDP).  A sural nerve biopsy is performed.  What is the structure indicated by the arrow in this image...

Twitter Poll (February 3, 2021)

SAP, Serum amyloid protein P, twitter poll, renal pathology, arkana laboratories
Answer: C) SAP Serum amyloid protein P (SAP) has been found to be a highly sensitive and specific marker for the diagnosis of Membranous-Like Glomerulopathy with Masked IgG Kappa Deposits. Of note, while these cases show light chain restriction by immunofluorescence, most patients do not have evidence of an underlying paraprotein. For further information about this interesting entity, please see the following references. References Larsen CP, Sharma SG, Caza TN, et al. Serum amyloid P deposition is a sensitive and specific feature of membranous-like glomerulopathy with masked IgG kappa deposits. Kidney Int 2020 Mar;97(3): 602-608. Larsen CP, et al. Membranous-like...