Cri du chat syndrome

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Cri du chat syndrome


Genetic disorders


Alagille syndrome (NORD)

Familial adenomatous polyposis

Familial hypercholesterolemia

Hereditary spherocytosis

Huntington disease

Li-Fraumeni syndrome

Marfan syndrome

Multiple endocrine neoplasia

Myotonic dystrophy


Polycystic kidney disease

Treacher Collins syndrome

Tuberous sclerosis

von Hippel-Lindau disease




Cystic fibrosis

Friedreich ataxia

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


Krabbe disease


Mucopolysaccharide storage disease type 1 (Hurler syndrome) (NORD)

Niemann-Pick disease type C

Niemann-Pick disease types A and B (NORD)

Phenylketonuria (NORD)

Polycystic kidney disease

Primary ciliary dyskinesia

Sickle cell disease (NORD)

Tay-Sachs disease (NORD)

Wilson disease

Cri du chat syndrome

Williams syndrome

Angelman syndrome

Prader-Willi syndrome

Beckwith-Wiedemann syndrome

Mitochondrial myopathy

Klinefelter syndrome

Turner syndrome

Fragile X syndrome

Friedreich ataxia

Huntington disease

Myotonic dystrophy

Down syndrome (Trisomy 21)

Edwards syndrome (Trisomy 18)

Patau syndrome (Trisomy 13)

Alport syndrome

Fragile X syndrome

Fabry disease (NORD)

Glucose-6-phosphate dehydrogenase (G6PD) deficiency


Lesch-Nyhan syndrome

Mucopolysaccharide storage disease type 2 (Hunter syndrome) (NORD)

Muscular dystrophy

Ornithine transcarbamylase deficiency

Wiskott-Aldrich syndrome

X-linked agammaglobulinemia

Autosomal trisomies: Pathology review

Miscellaneous genetic disorders: Pathology review

Muscular dystrophies and mitochondrial myopathies: Pathology review


Cri du chat syndrome


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USMLE® Step 1 questions

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High Yield Notes

4 pages


Cri du chat syndrome

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USMLE® Step 1 style questions USMLE

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A 3-hour-old female neonate is being evaluated in the newborn nursery for hypotonia. The infant was born via vaginal delivery to a 25-year-old mother, who did not have a perinatal follow-up. Family history is non-contributory. The patient’s birth weight is below the 5th percentile, height at the 6th percentile, and head circumference at the 3rd percentile. On examination, the child appears hypotonic, and her cry is high-pitched and cat-like. In addition, she has a moon face, hypertelorism, a flat nose, and a prominent nasal bridge. Which of the following is most likely responsible for this patient’s condition?  

External References

First Aid








Cri-du-chat syndrome p. 62

Epicanthal folds

cri-du-chat syndrome p. 62


cri-du-chat syndrome p. 62

Ventricular septal defect (VSD) p. 305, 728

cri-du-chat syndrome p. 62


Cri du chat syndrome is a rare genetic disorder caused by a genetic mutation where a portion of chromosome 5 is deleted, or missing. The name is a French term that refers to the characteristic high-pitched cry of the affected babies, which sounds like the cry of a cat or “le cri du chat”.

Alright, let’s break this down. Our DNA is packaged up into 46 chromosomes, which contains the genes that are pretty much instructions for making proteins. These proteins control everything from growth and development to the day-to-day functioning of the cells. Each of the 46 chromosomes is actually made up of a pair of chromosomes and you get one from each parent, so 23 pairs. Now, these chromosomes have two rod-shaped arms, one short and one long, hooked together in the middle by a centromere. These two short arms are referred to as p arms from the French term “petit” that means small. In cri du chat syndrome, a part of one of the short arms of chromosome 5 is missing and so cri du chat syndrome is also known as 5p deletion syndrome, or 5p minus.

Okay, so 80-85% of the cases of cri du chat syndrome are the result of de novo deletion, which means they occur on their own without being inherited. However, in 10% of the cases, the deletion is inherited from a parent who has a balanced translocation. Translocation means that a part from one chromosome switches places with a part from another chromosome. and it’s balanced when there is no genetic material gained or lost, so the person doesn’t experience any adverse affect. As an example, let’s say this woman has 23 pairs of normal chromosomes. And here is her boyfriend, and in his karyotype we can see that a part of chromosome 5 has switched places with a part of chromosome 11. But he remains normal because no genetic material is gained or lost. But if these two have a baby, the baby will randomly inherit 2 copies of each chromosome, one from mom and one from dad. Now since both mom and dad have two copies of each chromosome, if the dad passes on the translocated chromosome 5, but the normal chromosome 11, the translocated information from chromosome 5 will be lost. So in this case, the balanced translocation in the father will become unbalanced translocation in the child because some genetic material from chromosome 5 is lost and this baby will have cri du chat syndrome.

Alright now symptoms of cri du chat syndrome vary and depend upon the amount of missing genetic material. The most specific feature is obviously the cat-like cry and it’s due to structural abnormalities of the larynx. Surprisingly, someone can have cri du chat syndrome without having this characteristic “meowing”. Also, they usually have characteristic facies with a small, round face with full cheeks, hypertelorism, or increased distance between the eyes, prominent supraorbital arches, which are the bony ridges above the orbits, and epicanthal folds, or skin folds of the upper eyelids that cover the inner angles of the eyes. In addition, the nose is usually flat with a wide nasal bridge, the ears are low-set, there’s dropped jaw due to increased facial laxity, and dental malocclusion, or misalignment of the teeth. Besides abnormalities in the head and neck, It causes congenital heart defects such as ventricular septal defects. There’s also neurological problems including moderate to severe intellectual disability and slower motor development, leading to delayed walking and clumsiness. Other common characteristics of babies with cri du chat syndrome include failure to thrive and hypotonia, or weak muscle tone, which may become hypertonia later in life. These babies tend to have chronic medical problems include feeding problems because they have difficulty swallowing, constipation, and recurrent infections like otitis media, respiratory infections and urinary tract infections.


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