Post Type Archives: Topics

Addison disease is a disorder resulting from progressive destruction of the adrenal cortex. Most common cause of chronic adrenal insufficiency/ Addison disease in the Western world (developed world) is the autoimmune adrenalitis, in developing world Tuberculosis is the most common cause. … … Pathogenesis More than 90% of cases of Addison disease can be attributed […]

Alport syndrome is a rare genetic disorder characterized by progressive hereditary nephritis with hematuria secondary to basement membrane disease of the glomeruli. It is a type of hereditary nephritis with high-frequency sensorineural hearing loss (SNHL) and pathognomonic ocular lesions (Lenticonus).
Pathogenesis

The most common mode of inheritance is X-linked, and men are more severely affected (obviously like most X-linked diseases).

Collagen type IV mutation that results in an abnormal basement membrane. Type IV collagen is crucial for normal function of the lens, cochlea, and glomerulus. It is made up of heterotrimers of α3, α4, and α5 chains. Mutation of any one of the α chains results in defective heterotrimer composition and manifest as Alport syndrome.

collagen α5 chain is the most commonly affected one in Alport Syndrome. (60-70% cases).

Clinical manifestation

Renal involvement

Renal biopsy appear unremarkable until late in the course. With progression of illness there will be glomerulosclerosis, vascular sclerosis, tubular atrophy, and interstitial fibrosis. These changes lead to end stage renal disease and renal failure. 

Electron microscopy reveals GBM (glomerular basement membrane thinning and splitting with irregular foci of thickening yielding a “basket weave” appearance. 

Microscopic or frank hematuria persistent from childhood constitutes the clinical clue for its early recognition. Patient presents with hematuria and proteinuria.

Ocular involvement

Anterior lenticonus is a hallmark for ocular manifestation of AS. However, posterior lenticonus is also seen in some cases. Lens capsule has three-dimensional molecular meshwork, primarily of type IV collagen and other extracellular matrix constituents. Mutation in the gene that codes for type IV collagen results in capsule fragility, leading to conical protrusion of the capsule at its weakest point which is giving rise to lenticonus. Anterior lenticonus is more commonly seen than posterior, which leads to progressive lenticular myopia developing by the second decade as seen in our patient.

Dot and fleck retinopathy is also seen in few cases.

Hearing defect

Progressive sensorineural hearing loss beginning with high frequencies.

An insulinoma is NET (neuroendocrine tumors) of the pancreas, derived from beta cells that ectopically secrete insulin, which results in hypoglycemia. Insulinoma is a rare pancreatic islet cell tumor, the most common cause of hypoglycemia related to endogenous hyperinsulinism. Most insulinomas are solitary and benign. The average age of occurrence is 40–50 years old. Clinical […]

Whipple’s disease is a chronic infection caused by Tropheryma whipplei. T. whipplei is a weakly staining gram-positive bacillus. It has predilection for causing disease in middle-aged Caucasian men who are farmers. Whipple’s disease mainly causes malabsorption but may affect other parts of the body including the heart, brain, joints, skin, lungs and the eyes. … […]

Listeria monocytogenes is a facultatively intracellular, gram-positive rod that grows over a broad temperature range, including refrigeration temperatures. This organism is motile during growth at low temperatures, demonstrating tumbling motility at low temperatures. At body temperature (37°C) it induces actin polymerization in host cell actin and forms “rocket tails” that facilitates intracellular movement and cell-to-cell spread across cell membranes, this way it avoids antibodies too.

Fragile X syndrome is the disease in which mutation occurs in a long repeating sequence of three nucleotides. Fragile X syndrome results from a mutation in the FMR1 gene, which maps to Xq27.3. FMR1 gene codes for familial mental retardation protein (FMRP). When the number of trinucleotide repeats exceeds approximately 230, the gene becomes abnormally […]

Sjogren syndrome is a chronic disease caused by immunologically mediated destruction of the lacrimal and salivary glands. It is characterized by dry eyes (keratoconjunctivitis sicca) and dry mouth (xerostomia). Sjogren’s  syndrome is slowly progressing autoimmune disease characterized by lymphocytic infiltration of the exocrine glands. The major infiltrating cells in the affected exocrine glands are activated […]

Type II Hypersensitivity is an antibody mediated process in which IgG and IgM antibodies are directed against antigens on cells or extracellular material. This subsequently leads to cell lysis, tissue damage or loss of function. … … Antibodies – IgG and IgM antibodies Target antigens Intrinsic- The antigens may be normal molecules intrinsic to cell […]

Type 1 hypersensitivity is a tissue reaction that occurs within minutes after the interaction of antigen with IgE antibody bound to the surface of mast cells (sensitized mast cells). The reaction is initiated by entry of an antigen, which is called an allergen because it triggers allergy. Allergens are products for which certain individuals are […]

Chediak-Higashi syndrome is a rare autosomal recessive disorder characterized clinically by partial oculocutaneous albinism due to defects in melanin granules and recurrent pyogenic bacterial infections due to abnormalities in granulocytes. The basic defect is in microtubules resulting in fusion of lysosomal granules. All white blood cells contain abnormally giant granules. … … … What is […]