BMS314 Lecture Notes - Lecture 21: Amyloid Beta, Foreign Body, Osteolysis
PIS
• A miscellaneous group of disorders which are a result of the accumulation of a normal
substance in abnormal amounts OR an abnormal substance, which are either inside cells or
between cells.
• Traditionally they are grouped together due to the histological presence of their material
however there pathogenesis and aetiologies are very diverse
• Related by the result of either intra or extracellular accumulation of material
Where do pigments, infiltrates and storage diseases fit in???
• Something added - cells, fluid, storage material
• Something lost - cells (necrosis)
• Something changes - adaptive responses, congenital anomalies, colour
Diseases that manifest as changes in pigment or accumulations of storage material have diverse
pathogeneses
• Many of these diseases result from metabolic derangements in cells
• They manifest as the intracellular accumulation or infiltration extracellular of abnormal
amounts of a variety of substances that fall into 3 categories
o Normal cellular constituent which accumulates in excess
o An abnormal substance which can be exogenous (formed outside the body) or
endogenous (formed inside the body)
o Pigments
• This slide is an overview of what we will cover
• Tattoos
o The pigments are introduced via a needle into the dermis
• A proportion is removed by macrophages and the rest remains deep in the dermis
• This pigment is often drained into lymph nodes
• Carbon
o The most common exogenous pigment found in animals
o Apart from tattoos the most common route of entry is the inhalation of inert particles
(often causes anthracosis which is the accumulation in the lungs)
• The alveoli contain numerous macrophages which contain lots of carbon particles within their
cytoplasm obscuring their cellular detail
o If this continues to accumulate will cause black discolouration of the pulmonary and
pleural surfaces
• Doesn't always result in gross lesions, can be only a few particles present
• Carbon is inert, therefore will remain but with minimal effects
• Left = melanin
• Right = jaundice due to an excess In billirubin
• Melanin is normally present in the epidermis and multiple other tissues
• Responsible for skin and hair colour
• Melanocytes produce melanin
• In the skin these are present in the basal epidermis and they transfer there pigment to protect
the genetic material within the nuclei from UV damage
• Melanin is formed from the oxidation of tyrosine via the enzyme tyrosinase
• This enzyme contains copper
o Therefore nutritional copper deficiency will results in a fading of colour
• Here is a dermal accumulation of melanin
• It can be normal to have congenital melanosis (black spots forming multifocal areas of
melanin)
• Often seen in the meninges of the brain
• Common in some animals
Document Summary
Something changes - adaptive responses, congenital anomalies, colour. If this continues to accumulate will cause black discolouration of the pulmonary and pleural surfaces: doesn"t always result in gross lesions, can be only a few particles present, carbon is inert, therefore will remain but with minimal effects. Left = melanin: right = jaundice due to an excess in billirubin, melanin is normally present in the epidermis and multiple other tissues, responsible for skin and hair colour, melanocytes produce melanin. The albinos possess melanocytes which are normal histologically in appearance they are just non functional. Disrupt melanocyte function or destroy melanocytes: derived from oxidation and incomplete lysosomal degradation of unsaturated fat from lipid waste products of cell catabolism. Lipofuscin (wear and tear pigment) age related pigment. Looks like a faint yellow brown granular pigment: grossly - if it accumulates in large amounts - it is referred to as "brown atrophy" (doesn"t actually involve atrophy)
