When the tissue pretreated with potassium permanganate is stained with Congo-red stain, the apple-green birefringence is abolished. The tissue is likely to contain which type of amyloid?

Ans. a (AA amyloidosis) (Ref. Textbook of pathology by Harsh Mohan 5th ed., 22).# The Congo red stain can also be used to distinguish between AA and AL amyloid.# The Congo red staining is the most reliable method for demonstrating amyloid, after electron microscopy.# AA amyloid fails to stain with Congo red if pretreated with potassium permanganate. while AL and other forms do not do so.AMYLOIDOSISDefinition:# Deposition of various types of protein aggregations that share specific traits when examined microscopically and are specifically, extracellular, thioflavin stain positive, and exhibit apple-green birefringence when stained with Congo red and characterized by a cross-beta sheet quaternary structure.# Genetically transmitted amyloid diseases are often inherited in an autosomal dominant fashion.Types of Amyloidosis# Systemic amyloidosis- Primary amyloidosis* Mutations in lysozyme, transthyretin, apolipoprotein B, fibrinogen- Secondary amyloidosis* AA amyloidosis (amyloid A protein, an acute phase protein due to chronic inflammation)* AL amyloidosis (immunoglobulin light chains)* Gelsolin amyloidosis (plasma gelsolin fragments).* Familial or hereditary amyloidosis- Most commonly caused by mutations in the transthyretin protein, but in rare occurrences can also be caused by apolipoprotein Al, gelsolin, fibrinogen, and lysozyme mutations.# Organ-specific amyloidosis- Diabetes mellitus type 2 (amylin, also known as IAPP)- Neurology:* Alzheimer's disease (Ab 39-42)* Parkinson's disease (alpha-synuclein)* Huntington's disease (huntingtin)* Spongiform encephalopathies- Creutzfeldt-Jakob disease (PrP in cerebrum)- Kuru (diffuse PrP deposits in brain)- Fatal familial insomnia (PrP in thalamus)- Bovine spongiform encephalopathy (PrP in cerebrum)* Congophilic angiopathy (Amyloid beta)DiseaseAmyloid typePrimary amylodosis (e.g., plasma cell disorders)Secondary amyloidosis (e.g., neoplasia, RA, TB, SLECrohn's, osteomyelitis, familial Mediterranean fever)AL (Kappa or lambda chains)AA (from serum amyloid A )Renal hemodialysisSenile cerebral amyloidosisAmyloid protein Ab2M and fibrillary protein b2 microglobulinAmyloid protein Ab and fibrillary protein -amyloid precursor protein (BAPP)Cardiac amyloidosisMedullary carcinoma of thyroidType 2 diabetes, pancreatic islet-cell tumorsAmyloid protein ATTR and fibrillary protein transthyretinProcalcitoninAmylinMethods of diagnosis:# Indirect methods:- Iodine stains- Fluorescent stains- Metachromatic stains (Rosaniline dyes)- Stain polarimetry (Congo red staining)- Immunological methods- Circular dichroism, or FTIR# Direct methods:- X-ray crystallography and infrared spectroscopyHistological staining properties:Change in the fluorescence intensity of aromatic dyesSuch as Thioflavin T or Congo Red.Congo red stainOrange colourIn polarized lightThe Congophillic amyloid plaques generally show apple-green birefringence due to cross-beta-pleated sheet configuration.# Amyloid biophysics- The "gold-standard" test to see if a structure is amyloid is by placing a sample in an X-ray diffraction beam.- X-ray crystallography and infrared spectroscopy demonstrate a characteristic cross p-pleated sheet conformation.- By electron microscopy, amyloid is seen as made up largely of non-branching fibrils of indefinite length and a diameter of approximately 7.5 to 10 nm.