Chapter 6: Genetic Disorders Pathology

Genetic Disorders Pathology begins with cytogenetic abnormalities involving autosomes, detailing the pathogenesis and clinical features of common trisomies such as Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Patau syndrome (trisomy 13), alongside structural abnormalities like Robertsonian translocations and chromosomal deletions seen in Cri du chat syndrome. The discussion extends to sex chromosome disorders, specifically delineating the phenotypes of Klinefelter syndrome and Turner syndrome, as well as disorders of sexual development and the principles of X-inactivation. A significant portion of the text focuses on Mendelian disorders resulting from single-gene mutations, classifying them into autosomal recessive, autosomal dominant, and X-linked inheritance patterns. Key autosomal recessive conditions explored include Cystic Fibrosis (caused by CFTR gene mutations), metabolic enzymopathies like Phenylketonuria (PKU), Alkaptonuria, and Albinism, as well as glycogen storage diseases (Von Gierke, Pompe, McArdle) and lysosomal storage diseases such as Tay-Sachs, Niemann-Pick, and Gaucher disease. The chapter also analyzes autosomal dominant pathologies, including Familial Hypercholesterolemia, connective tissue disorders like Marfan syndrome and Ehlers-Danlos syndrome, and tumor suppressor defects seen in Neurofibromatosis and Von Hippel-Lindau disease. Furthermore, the text covers X-linked conditions such as Lesch-Nyhan syndrome, classical hemophilia patterns, and Fragile X syndrome, distinguishing them from trinucleotide repeat disorders like Huntington disease. The summary concludes by explaining non-Mendelian inheritance patterns, including genomic imprinting examples like Prader-Willi and Angelman syndromes, mitochondrial DNA disorders which exhibit exclusive maternal inheritance, and multifactorial conditions influenced by both polygenic and environmental factors.