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There are two broadcategories of pigments,
endogenous andexogenous
Pigments
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Endogenous pigmentsMelanin
Melanin is the brown-black, non-haemoglobin derived pigment present in the hair, skin, choroidof the eye, meninges and adrenal medulla.Various disorders of melanin pigmentation cause
generalized and localized hyperpigmentation:i) Generalized hyperpigmentation e.g. in Addison's
disease, chloasma observed during pregnancy.ii) Focal hyperpigmentation e.g. caf-eu-lait spots,
melanotic tumours.iii) Generalised Hypopigmentation: albinism is an
extreme degree of generalised hypopigmentation.iv) Localised hypopigmentation e.g. leucoderma,
vitiligo.
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Alkaptonuria
This is a rare autosomal recessivedisorder in which there is deficiencyof an oxidase enzyme required for
break down of homogentisic acidwhich then accumulates in thetissues and is excreted in the
urine(homogentisic aciduria). Thepigment is melanin-like and isdeposited both intracellularly and
intercellularly in the cartilages,
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Haemoprotein-derived pigments
Haemoproteins are the mostimportant endogenous pigmentsderived from haemoglobin,
cytochromes and their break-downproducts. In disordered ironmetabolism and transport,
Haemoprotein-derived pigmentsaccumulate in the body. Thesepigments are haemosiderin, acid
haematin(haemozoin), bilirubin, and
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parenchymatous deposition of haemosiderin in liver, pancreas,kidney, and heart.Reticuloendothelial deposition in
the liver, spleen, and bonemarrow. Generalised or systemicoverload of iron may occur due to
the following causes:i) Increased erythropoietic activityii) Excessive intestinal absorption of
iron
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ACIDHAEMATIN(HAEMOZOIN)
It is a Haemoprotein-derived-brown-blackpigment containing haemiron in ferric form in acidic
medium. Haematinpigment is seen most
commonly in chronic
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BILIRUBINBilirubin is the normal non-ironcontaining pigment present in the bile. Itis derived from porphyrin ring of thehaem moiety of haemoglobin. Excess of
bilirubin or hyperbilirubinaemia causesan important clinical condition called
jaundice. Jaundice may appear in one of
the following 3 ways:a) prehepatic or haemolyticb) Posthepatic or obstructive
c) hepatocellular
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PORPHYRINSPorphyrins are normal pigmentpresent in haemoglobin,
myoglobin and cytochrome.Porphyria refers to anuncommon disorder of inborn
abnormality of porphyrinmetabolism. Porphyrias are of two broad types:
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po usc n wear an ear pigment)
Lipofuscin or lipochrome isyellowish-brown intracellular lipid pigment. The pigment isoften found in atrophied cells of old age and hence name wear and tear pigment. It is seen inthe myocardial fibres,hepatocytes, leydig cells of thetestes and in neurons in senile
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Microscopic appearance
The pigment is coarse, golden-brown granular and often
accumulates in the central partof the cells around the nuclei. Inthe heart muscle, the change is
associated with wasting of themuscle and is commonlyreferred to as brown atrophy of
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PIGMENTSEXOGENOUS pigments are the pigments introduced intothe body from outside such as inhalation, ingestion or inoculation.
INHALED PIGMENTS Anthracosis(deposition of carbon particles) is seen in
almost every adult lung and generally provokes noreaction of tissue injury
INGESTED PIGMENTSChronic ingestion of some metals may produce
pigmentation, e.g. argyria, chronic lead poisoning,melanosis and carotenaemia .
INJECTED PIGMENTS(TATTOOING)Pigments like India ink, cinnabar and carbon are injected in
the process of tattooing.