00:00 / 00:00
Evolution and natural selection
Independent assortment of genes and linkage
Mendelian genetics and punnett squares
Alagille syndrome (NORD)
Familial adenomatous polyposis
Multiple endocrine neoplasia
Polycystic kidney disease
Treacher Collins syndrome
von Hippel-Lindau disease
Gaucher disease (NORD)
Glycogen storage disease type I
Glycogen storage disease type II (NORD)
Glycogen storage disease type III
Glycogen storage disease type IV
Glycogen storage disease type V
Mucopolysaccharide storage disease type 1 (Hurler syndrome) (NORD)
Niemann-Pick disease type C
Niemann-Pick disease types A and B (NORD)
Primary ciliary dyskinesia
Sickle cell disease (NORD)
Tay-Sachs disease (NORD)
Cri du chat syndrome
Fragile X syndrome
Down syndrome (Trisomy 21)
Edwards syndrome (Trisomy 18)
Patau syndrome (Trisomy 13)
Fabry disease (NORD)
Glucose-6-phosphate dehydrogenase (G6PD) deficiency
Mucopolysaccharide storage disease type 2 (Hunter syndrome) (NORD)
Ornithine transcarbamylase deficiency
Autosomal trisomies: Pathology review
Miscellaneous genetic disorders: Pathology review
Muscular dystrophies and mitochondrial myopathies: Pathology review
0 / 8 complete
Cri Du Chat
At the clinic, 30 year old Linda comes with her 2 year old toddler for a yearly pediatric checkup. Linda tells the pediatrician that, while she was bathing her son, she noticed that his testes are unusually large. Clinical examination confirms enlarged testes, and additionally, the pediatrician noticed dysmorphic facial features including a long, narrow face; prominent forehead and jaw; and large, protruding ears. Later that day, 27 year old Samantha comes to the clinic with her 5 year old son because she noticed that he often has strange episodes of laughter and smiling. In addition, she mentions that he had experienced seizures several months ago.
Based on the clinical findings, the pediatrician concludes that both children have some form of genetic disorder, and orders genetic testing to confirm the diagnosis. Now, let’s go over genetic disorders such as fragile X syndrome, imprinting disorders, Cri-du-chat syndrome, and Williams syndrome.
First, let’s start with fragile X syndrome. This is an X-linked disorder caused by inactivation of the FMR1 gene, which is located on the long arm of the X chromosome. These individuals have over 200 CGG trinucleotide repeats on the FMR1 gene, which leads to its hypermethylation and subsequent inactivation. Fragile X syndrome is the most common cause of inherited intellectual disability, and the second most common cause of genetically associated psychiatric disorders, after Down syndrome. Individuals with fragile X syndrome can have delayed speech and motor development. In addition, individuals may have anxiety disorders, autism, and attention deficit-hyperactivity disorder; as well as mitral valve prolapse. For your exam, it’s important to know the key physical findings of fragile X syndrome includes enlarged testes, also known as macroorchidism; and dysmorphic facial features, like a long narrow face, with large protruding ears, and prominent forehead and jaw. The treatment of fragile X syndrome includes speech, occupational, and physical therapy. Clinicians should also focus on the prevention of common medical problems associated with the disorder such as gastroesophageal reflux, sinusitis, and otitis media.
Latest on COVID-19
Nurse Practitioner (NP)
Physician Assistant (PA)
Create custom content
Raise the Line Podcast
Copyright © 2024 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Cookies are used by this site.
Terms and Conditions
USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.