SEARCH RESULTS FOR: Turner-Syndrome-Pathogenesis-and-Clinical-Findings

Turner Syndrome Pathogenesis and Clinical Findings

Turner Syndrome: Pathogenesis and clinical findings Author: Simran Pherwani Ashar Memon, Christy Chong Reviewers: Tara Shannon Simran Sandhu, Mao Ding Danielle Nelson* * MD at time of publication Non-disjunction in phenotypically female gametes (i.e. homologous X-chromosomes or sister chromatids fail to separate) Partial or complete absence of second sex chromosome, leaving only one normal X-chromosome Possible Chromosomal Profiles Other meiotic error → deletion or misdivision of X-chromosomal material Complete loss of one X- chromosome in all cells (45,X) (45%) Skeletal Abnormalities ↓ Expression of SHOX gene (present on X- and Y-chromosomes) ↓ Cellular proliferation in growth plates of bones in extremities during embryonic development Short stature High-arched palate Genu valgum (knock knees) Micrognathia (smaller lower jaw) Broad chest Cubitus valgus (forearm angled outward) Mosaicism (complete loss of one X-chromosome in some cells (e.g., 45,X/46,XXX, etc)) (50%) Congenital Heart Defects (most serious) Single copy of TIMP1 gene and presence of risk TIMP3 allele, and differential expression of KDM6A gene Bicuspid aortic valve Aortic coarctation Aortic dilation (worsened by hypertension) One X-chromosome and presence of Y-chromosomal material in some or all cells (e.g., 45,X/46,XY) Presence of an X- isochromosome (most commonly i(Xq)) Other structural abnormalities of X-chromsome (e.g., Ring Chromosome X, partial deletion of X, X or Y marker chromosome) Endocrine Disorders Turner Syndrome The most common sex chromosomal abnormality in females (affects 1/2000-3000) Results in deletion or non- functioning of one X chromosome Clinical presentations vary depending on chromosome profile Aortic dissection Renal disease Neurocognitive Deficits Mechanism unknown Deficit in social skills Specific (non-verbal) learning disorder (otherwise normal intelligence) ↓ Executive function skills ↓ Visuospatial skills ↓ Attention Accelerated follicular apoptosis (i.e., loss of oocytes from ovaries) → streak gonads Ovaries are unable to respond to high gonadotropins (FSH, LH) Hypergonadotropic hypogonadism Premature ovarian insufficiency ↓ Expression of immune- associated genes on X- chromosome ↑ Autoimmunity Autoimmune diseases (celiac, thyroiditis, IBD, metabolic abnormalities) ↓ Estrogen levels Lack of breast development ↑ Liver enzymes (Additional mechanisms likely) ↓ Bone mineral density Other Dysmorphic Features Lymphedema Webbed (buildup of lymph neck fluidàswelling) Primary amenorrhea Infertility Legend: Pathophysiology Mechanism Sign/Symptom/Lab Finding Complications Published November 25, 2023 on www.thecalgaryguide.com