Cell Tissue Accumulation: Gout and Glycoproteins

• Tissue accumulations in cells are caused by metabolic derangements

Gout

• Gout is a disturbance in purine metabolism
• It leads to the deposition of sodium urate in tissues, increasing its levels in blood and urine
• This mainly affects the skin, kidneys, and joints, particularly the metatarsophalyngeal joint of the big toe
• Primary causes are often familial with a higher prevalence in males and is due to increased purine breakdown or decreased its clearance
• Secondary causes include increased cellular destruction, seen in conditions like polycythemia rubra vera

Glycoproteins and CHate

• Glycogen accumulation occurs in Glycogen storage diseases
• This is caused by abnormal glycogen metabolism
• Microscopically, cells appear swollen with clear cytoplasmic vacuoles
• Mucin accumulation examples include catarrhal inflammation and mucoid carcinoma
• Microscopically, cells are swollen with mucin, appearing as signet-ring cells
• Special stains like PAS (Periodic Acid Schiff) are positive for glycogen
• Cells with mucin may rupture, leading to mucin depletion

Hyalinosis (Hyaline deposition)

• Hyalinosis involves the presence of glassy, refractile, homogenous, and structureless protein material
• This material stains red with eosin
• Examples include Russell's bodies in Rhinoscleroma and Corpora amylacia in prostatic hyperplasia

Amyloidosis

• Amyloidosis is the extracellular deposition of abnormal fibrillary protein, appearing as homogenous eosinophilic material
• It causes progressive organ dysfunction due to vascular compression and pressure atrophy

Classification of Amyloidosis

• Localized forms include nodular deposits affecting the tongue, larynx, or lung
• Systemic (generalized) forms include primary amyloidosis in plasma cell tumors (multiple myeloma)
• Secondary amyloidosis occurs in inflammatory diseases like tuberculosis (TB)
• Other forms include senile (cardiac or cerebral, as in Alzheimer's) and heredofamilial amyloidosis
• Endocrine amyloidosis occurs in endocrine tumors

Diagnosis of Amyloidosis

• Diagnosis involves tissue biopsy
• Hx & E stain shows esinophilic
• Congo red stain turns orange-red
• Under polarized light, Congo red appears apple green

Pathological Calcification

• Pathological calcification is the abnormal deposition of calcium salts in tissue other than bone and teeth
• On macroscopic examination, it appears chalky white and hard (N/E)
• Microscopically, it appears dark blue (M/E)

Types of Calcification

• Dystrophic calcification occurs in nonviable tissue with normal blood calcium levels and is the most common form
• Metastatic calcification occurs in viable tissue with hypercalcemia
• Stone formation occurs in gland ducts

Dystrophic Calcification Examples

• Fat necrosis
• Walls of chronic abscesses
• Old scars
• Dead bilharzial ova
• Fibrosed valves
• Atheroma of large vessels

Metastatic Calcification Causes

• Excess absorption of calcium from the intestine, as in hypervitaminosis D or milk-alkali syndrome.
• Excess mobilization of calcium from bone, as in endocrinal disorders
• Ex: hyperparathyroidism, thyrotoxicosis, and Cushing syndrome
• Prolonged immobilization in bed
• Bone destruction by malignant tumors

Metastatic Calcification Sites

• Kidney (in tubules, known as nephrocalinosis)
• Walls of Arteries
• Mucosa of the stomach
• Lung alveoli

Stone Formation Sites

• Biliary tract
• Urinary tract
• Salivary gland

Pathological Pigmentation

• Pigments are colored substances that stain tissues
• They can be exogenous or endogenous

Exogenous Pigments

• Exogenous pigments enter the body via inhalation (anthracosis from carbon particles)
• Or ingestion (chronic lead poisoning/plumbism)
• Or inoculation (tattooing)

Endogenous Pigments

• Melanin is a pigment that cases hyperpigmentation (localized: nevus, melanoma)
• Melanin is also responsible for generalized hyperpigmentation (prolonged exposure to sunlight)
• Melanin is also responsible for hypopigmentation (localized: vitiligo, generalized: albinism)
• Lipochrome (lipofuscin) is a yellowish-brown, fat-soluble pigment normally present in the heart, testis, seminal vesicles, corpus luteum, and adrenal cortex
• Its accumulation increases with tissue breakdown
• This leads to release of phospholipids that are phagocytosed by neighboring cells, causing intracellular accumulation
• Causes include old age (brown atrophy of the heart), wasting diseases, and cancer cachexia
• Hemosiderin is an iron-containing brown pigment
• Special stains like Prussian Blue are used to stain it
• Localized hemosiderosis occurs due to localized hemorrhage
• Generalized hemosiderosis can be primary (due to inborn errors of metabolism) or secondary
• Secondary: repeated blood transfusions or hemolytic anemias