• The tumors may cause bumps under the skin, colored spots, skeletal problems, pressure on spinal nerve roots , and other neurological problems.
1-Neurofibromas, café-au-lait, Lisch nodules
NEUROFIBROMATOSIS 1- (von Recklinghausen) • Is a tumor disorder that is caused by the mutation of a gene on chromosome 17 that is responsible for control of cell division. • NF-1 causes tumors along the nervous system. • Common symptoms of NF-1 include • scoliosis (curvature of the spine), • learning disabilities, • vision disorders, Lich nodules ( • and epilepsy.
Cutaneous neurofibromas and a 'café au lait spot' Back of an elderly woman with NF-1 Lisch nodules a pigmented hamartomatous nodular aggregate of dendritic melanocytes affecting the iris
NEUROFIBROMATOSIS 2- Bilateral acoustic neuromas and multiple meningiomas • Manifested by the development of symmetric, non- malignant brain tumors in the region of the cranial nerve VIII, • which is the "auditory-vestibular nerve" that transmits sensory information from the inner ear to the brain . • NF II is caused by mutations of the Merline gene which seems to influence the form and movement of cells • Many people with this condition also experience visual problems.
Hereditary Disease Caused by Sex-Linked Recessive Genes • Caused by defective genes carried on the X chromosome • Males affected more than women • Males inherit one defective gene on X from mother to have disorder • Females only affected if they inherit 2 defective genes (one from each parent)
Ex. Hemophilia • Caused by the inheritance of one recessive gene on the X (males) or two recessive genes on both X’s (females) • Affects blood – blood does not clot • Leads to severely increased risk of bleeding from common injuries • Potentially fatal
3. Chromosomal aberrations (cytogenetic disorders) • alternations in the number or structure of chromosomes • autosomes or sex chromosomes • studied by cytogenetics • cell cycle arrested in metaphase (colchicin) - staining by Giemsa method (G-bands) - photographing - karyotype • 2 sets of 23 chromosomes • 22 pairs of autosomes, 2 sex chromosomes (XX or XY) • cytogenetic disorders are relatively frequent ! (1:160 newborns; 50% of spontaneous abortions)
Structural abnormalities • breakage followed by loss or rearrangement • deletion, translocation Generally : • loss of chromosomal material is more dangerous than gain • abnormalities of sex chromosomes are better tolerated than autosomal • abnormalities of sex chromosomes sometimes symptomatic in adult age (e.g. infertility) • usually origin de novo (both parents and siblings are normal)
Numerical abnormalities • euploidy - normal 46 (2n) • polyploidy (3n or 4n) - spontaneous abortion • aneuploidy – trisomy (2n+1) - 47 - compatible with life – monosomy (2n-1) - • autosomal - incompatible with life • sex chromosomal- compatible with life • Deletion • Breakage
COMMON CYTOGENETIC DISEASES • AUTOSOMES – TRISOMY-21 ( DOWN SYNDROME) – 8, 9, 13 (Patau), 18 (Edwards), 22 – 22q.11.2 deletion • SEX CHROMOSOMES – KLINEFELTER : XXY, XXXY, etc.
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- Fall '19