Source / episode info

• **Episode:**138
• **Title:**Divine Intervention Episode 138 – The Clutch Genetic Diseases Podcast (especially for Step 2CK and Step 1) + Some Thoughts on The New 2CK Exam
• **Published:**2019-08-21
• Source:Episode page

One-liner

This episode provides a comprehensive review of high-yield genetic disorders, covering aneuploidies (Trisomy 21, 18, 13), sex chromosome abnormalities (47, XXY; 45, X), metabolic defects (PKU, Alkaptonuria, GSDs), and lysosomal storage diseases (Tay-Sachs, Niemann-Pick, Gaucher), emphasizing unique physical exam findings and biochemical mechanisms.

High-yield summary

• Down Syndrome (Trisomy 21): Most common trisomy; associated with endocardial cushion defects (AVSD) and increased risk of Alzheimer's disease by age 40. Maternal non-disjunction is the most common cause, linked to advanced maternal age.
• Autosomal Trisomies: Down Syndrome (Trisomy 21), Edwards Syndrome (Trisomy 18 - prominent occiput, overlapping digits, rocker bottom feet, poor prognosis); Patau Syndrome (Trisomy 13 - microcephaly, polydactyly, cleft lip/palate).
• Sex Chromosome Abnormalities: Klinefelter syndrome (47, XXY) presents with hypogonadism and infertility; Turner syndrome (45, X) presents with primary amenorrhea, short stature, and webbed neck.
• Metabolic Disorders: PKU is due to PAH deficiency, leading to buildup of phenylacetate/phenylpyruvate; Alkaptonuria involves homogentisic acid accumulation causing ochronosis in connective tissues.
• Lysosomal Storage Diseases (LSDs): Characterized by the inability to break down specific macromolecules, leading to cell swelling and organ dysfunction (e.g., Tay-Sachs: GM2 ganglioside; Niemann-Pick: Sphingomyelin).
• Glycogen Storage Diseases (GSDs): Type 1 (Von Gierke) affects the liver (hypoglycemia); Type II (Pompe) causes heart failure; Type III (Cori) affects liver and muscle; Type V (McArdle) affects only muscle.

Learning objectives

• Identify the characteristic physical findings associated with major aneuploidies (Trisomy 21, 18, 13).
• Differentiate between autosomal recessive and sex chromosome disorders based on inheritance patterns and clinical presentation.
• Correlate specific enzyme deficiencies with metabolic storage diseases (e.g., PAH deficiency -> PKU; Hexosaminidase A deficiency -> Tay-Sachs).
• Understand the differential pathophysiology of Glycogen Storage Diseases (GSDs) based on the affected organ/enzyme.
• Recognize the unique clinical features of syndromes like WAGR, Beckwith-Wiedemann, and Klinefelter syndrome.