What is the Difference Between Noonan Syndrome and Turner Syndrome

The key difference between Noonan syndrome and Turner syndrome is that Noonan syndrome is an autosomal dominant genetic disease that affects the development of various parts of the body, causing unusual facies and multiple malformations in both males and females, while Turner syndrome is a genetic disease that occurs due to sex chromosomal abnormality in females.

Noonan syndrome and Turner syndrome are two genetic diseases that share similar clinical features. Noonan syndrome can be misdiagnosed as Turner syndrome. They are growth hormone (GH)-deficient disorders. Both diseases affect the development of various body parts. Noonan syndrome affects both males and females, while Turner syndrome affects only females. In addition, short stature is associated with both genetic diseases.

CONTENTS

1. Overview and Key Difference
2. What is Noonan Syndrome  
3. What is Turner Syndrome
4. Similarities – Noonan Syndrome and Turner Syndrome
5. Noonan Syndrome vs. Turner Syndrome in Tabular Form
6. Summary – Noonan Syndrome vs. Turner Syndrome

What is Noonan Syndrome?

Noonan syndrome is a congenital genetic disorder and a development disorder described by Jacqueline Noonan in 1968. This disorder affects the normal development of various body parts. Major symptoms of Noonan syndrome are unusual facies, congenital heart disease, short stature, and chest deformity. Mental retardation is seen in 25 % of individuals who are affected by this syndrome. The prevalence of this disease is 1 in every 1000–2500 live births.

Patients with Noonan syndrome have a normal karyotype, which is 46 XX or 46 XY. This genetic disease arises due to a mutation on the long arm of chromosome 12. It is inherited in an autosomal dominant manner. The genes that cause Noonan syndrome are members of the RAS-MAPK signal transduction pathway. The first identified gene is PTPN11, and it accounts for about 30–60 % of cases.

This disease affects both males and females. Male patients may show undescended testes and abnormal Leydig cell function, causing hypogonadotropic hypogonadism. Female patients show normal pubertal development. They may have normal ovarian function but can also have delayed pubertal development. Recombinant human growth hormone therapy is one treatment method for Noonan syndrome.

What is Turner Syndrome?

Turner Syndrome is a genetic disease that affects females. It occurs due to the partial or complete absence of one X chromosome or having a structurally abnormal X chromosome. Structural anomalies can happen due to deletions in the short and long arms, duplications, ring chromosomes, or mosaicisms. The chromosomal makeup of these patients can be 45,XO or 45,X with mosaicism. The prevalence of this disease is 1 in 1500 to 2500 live female births.

The main symptoms of Turner syndrome are short stature, webbed neck, and congenital heart defects. Similar to Noonan syndrome, Turner syndrome is also associated with decreased growth hormone (GH) responsiveness. The most constant symptom of Turner syndrome is short stature. Ovarian failure is also a major problem of this disease. Intrauterine growth retardation is also can be seen in patients with Turner syndrome. Some treatment options for Turner syndrome patients are recombinant human GH, anabolic steroids, and estrogen therapy.

What are the Similarities Between Noonan Syndrome and Turner Syndrome?

• Noonan syndrome and Turner syndrome are two genetic disorders.
• Both are congenital disorders.
• They are growth hormone (GH)-deficient disorders that affect the normal development of various body parts.
• Both syndromes are associated with short stature.
• Treatment with recombinant human GH is an option for both diseases.

What is the Difference Between Noonan Syndrome and Turner Syndrome?

Noonan syndrome is a genetic disorder and an autosomal dominant disorder, while Turner syndrome is a genetic disease due to sex chromosome abnormality in females. Thus, this is the key difference between Noonan syndrome and Turner syndrome. Moreover, Noonan syndrome affects both males and females, while Turner syndrome affects only females.

The infographic below presents the differences between Noonan syndrome and Turner syndrome in tabular form for side-by-side comparison.

Summary – Noonan Syndrome vs. Turner Syndrome

Noonan syndrome and Turner syndrome are two genetic diseases that show similar clinical features. However, patients with Noonan syndrome have a normal karyotype, while patients of Turner syndrome have an abnormal karyotype of 45, XO or 45, X with mosaicism. So, this is the key difference between Noonan syndrome and Turner syndrome. Short stature is one of the most prominent clinical features in both diseases. Both diseases can be treated by recombinant human growth hormone therapy.

Reference:

1. Dahlgren, Jovanna, and Kerstin Albertsson-Wikland. “GH Responsiveness in Children with Noonan Syndrome Compared to Turner Syndrome.” Frontiers.
2. “Turner Syndrome: Causes, Symptoms, Diagnosis & Treatment.” Cleveland Clinic.

Image Courtesy:

1. “Noonan Syndrome” By National Human Genome Research (Public Domain) via Flickr
2. “A girl with Turner’s syndrome” By Sküskü15 – Own work (CC BY-SA 4.0) via Commons Wikimedia