Overview 

Aarskog-Scott syndrome is a rare X-linked recessive condition, which means that the mutation that causes it is present on the X chromosome. Because males only have one chromosome it means they are more likely to be affected by Aarskog-Scott syndrome than women, this is due to the fact that women have two X chromosomes and are therefore less likely to have mutations on both chromosomes meaning that there is compensation and this mean that typically women will have less symptoms than men. Aarskog-Scott syndrome is speculated to be caused by several mutations however, the only one that has been confirmed is a mutation in the FGD1 gene.¹

Causes of aarskog-scott syndrome 

Aarskog-Scott syndrome has been linked to the FDG1 gene, which is present on the X chromosome. If there is a mutation in the FDG1 gene, it causes the protein which is produced to be faulty, which in turn causes a disruption in signalling in Cdc42, which is important for the development of the baby before birth. However, it is speculated that other gene mutations are involved because approximately 20% of people with Aarskog-Scott syndrome have mutations in the FDG1 gene; therefore, it is likely that there are other genetic causes that have not been identified yet.

Aarskog-Scott syndrome can occur de novo (which means that it is not passed down by either parent) or it can be passed down genetically, where one of the parents is a carrier and passes the mutation down to their child. Due to the X-linked nature of the syndrome, it means that men cannot pass down the disorder to their daughters unless the mother is also a carrier of the mutation.²

Symptoms of aarskog-scott syndrome³

There are several different symptoms of Aarskog-Scott syndrome, and each patient may have a different degree of the symptoms. Some of which include: 

• Widely spaced eyes are also known as hypertelorism 
• A small nose and/or a long distance between the nose and mouth, also called the Philtrum 
• Widows peak hairline 
• Short stature during childhood, which usually catches up with peers when the child reaches puberty 
• short fingers known as brachydactyly
• Curved pinky fingers known as clinodactyly 
• Webbing of the skin between some fingers is also called cutaneous syndactyly 
• Heart defects 
• Split in the upper lip (cleft lip) and/or opening in the roof of the mouth (cleft palate) 
• Men with Aarskog-Scott syndrome commonly have a shawl scrotum meaning that their scrotum surrounds the penis instead of hanging below the penis, they also can have undescended testicles which is called cryptoorchidism 
• Mild learning difficulties are less common but can be a symptom

Diagnosis before birth 

If there is a family history of Aarskog-Scott syndrome, prenatal health providers may look out for short bone length during prenatal scans. Studies have shown that if there is no short-bone presentation during the first trimester when there is a family history of Aarskog-Scott syndrome, it is unlikely the baby will have Aarskog-Scott syndrome.

There is a lot of overlap between Aarskog-Scott syndrome and other X-linked disorders; therefore, if there is abnormal bone length is observed during a prenatal scan, the healthcare provider may suggest prenatal genetic testing. Genetic specialists will be able to perform laboratory tests such as karyotyping, which means that they will mark for genetic mutations on the chromosomes and determine if there are any mutations present. However, to be able to do this, they will require Fetal cells; therefore, procedures such as amniocentesis or chorionic villus sampling would have to be performed. These procedures are very similar as they both involve sticking a needle into the belly with the aid of an ultrasound and obtaining Fetal cells. The difference is that amniocentesis will be gathering amniotic fluid, which is a fluid that surrounds the baby. Whilst the chorion villus sampling involves obtaining a bit of the placenta. These tests may be recommended to you if there are suspicions that the baby has a genetic disorder. There are risks associated with the procedures that you must consider before making a decision, which include infection and miscarriage. Although these risks are rare, it is important to make a decision that feels best for you. 

A prenatal diagnosis may help you and the healthcare specialists to prepare for the possibility of having a child with a genetic disorder; however, it is important to note that you can perform genetic tests once the baby is born if you feel more comfortable with that decision.

Diagnosis after birth  

Diagnosis after birth is less likely to involve genetic testing, but it may potentially be used to help confirm the diagnosis of Aarskog-Scott syndrome. Some of the ways in which it may be diagnosed after birth are:

• Linking the facial, hand and genital features to the condition 
• X-rays can show the shorter bones that are common for the condition 
• An echocardiogram can show if there are heart defects 
• CT scan of the brain 
• X-ray scan for teeth 
• Ultrasound of the belly to check if the testicles are there instead of being descended

Treatment 

Aarskog-Scott syndrome does not have a cure, and it is not possible to prevent it from occurring. Some of the treatments may include surgery for symptoms; however, it depends on the severity of the symptoms. Growth hormone may be suggested to help patients grow if they have short bones.⁴

Overall 

Aarskog-Scott syndrome is an X-linked disorder that primarily affects males. it has a variety of symptoms and can be diagnosed before or after birth. There are risks of genetic testing that must be considered, and it is important for you to make the best choice for yourself based on the information provided.