What Is Hanhart Syndrome?

Overview

Hanhart syndrome, also known as hypoglossia-hypodactylia syndrome, aglossia-adactylia syndrome, or oromandibular limb hypogenesis syndrome, is a rare disorder of an unknown cause that primarily affects the development of the lower face and limbs in newborns. 

This condition is characterised by the absence or underdevelopment of the tongue as well as the absence or malformation of fingers or toes. It may also involve other abnormalities, such as cleft palate, abnormal ears, and heart disorders. The severity of the signs and symptoms can vary among patients. 

Hanhart syndrome requires individualised treatment to address a patient’s specific signs and symptoms, which may include improving impaired speech and addressing feeding difficulties.^1,2,3

Causes of Hanhart syndrome

The exact cause of Hanhart syndrome is not known. Some suspect that it has a genetic basis, although a specific gene associated with Hanhart syndrome has not been identified as of yet.^1,2

Ultimately, the underlying cause of Hanhart syndrome leads to issues during foetal development, resulting in the characteristic abnormalities that manifest in a newborn.²

Signs and symptoms of Hanhart syndrome

The key signs and symptoms of Hanhart syndrome include the absence or underdevelopment of the tongue, as well as the absence or malformation of fingers or toes. However, several other signs and symptoms may accompany these features:^1,2

• Impaired speech
• Difficulty in forming facial expressions
• Feeding difficulties
• Absent teeth
• Anormal ears
• Abnormal lip
• Cleft palate
• Absence or malformation of hands and feet
• Absent kidney
• Absent anal opening
• Disorders of the heart

Signs and symptoms of Hanhart syndrome can vary depending on the patient.^1,2,3

Diagnosis of Hanhart syndrome

Hanhart syndrome is often diagnosed by a doctor inspecting the newborn and sometimes using imaging techniques to detect the condition’s characteristic abnormalities. Several conditions should be ruled out when diagnosing Hanhart syndrome:^1,2

• Glossopalatine and ankylosis syndrome
• Splenogonadal fusion-limb defect syndrome
• Mobius syndrome

Inspecting the newborn

A doctor can inspect the newborn, allowing the condition’s characteristic abnormalities to be detected. While most signs and symptoms can be detected soon after birth, others, like impaired speech, difficulty in forming facial expressions, and absent teeth, may present later in an infant’s development.^1,2

Imaging techniques

Standard X-rays can be used to detect defects in limb development. Standard X-rays are a quick, painless procedure involving images being taken of the body.²

Computerised tomography, also known as a CT scan or CAT scan, can be useful in detecting jaw abnormalities. It uses X-rays but can create more detailed images than standard X-rays. Additionally, while standard X-rays only take a couple of minutes to complete, CT scans require 10 to 20 minutes of the patient lying still, and sometimes being asked to hold their breath at points, to capture body images. This makes them more challenging to perform in infants.²

Magnetic resonance imaging, also known as an MRI scan, produces detailed pictures of the body. In Hanhart syndrome, MRI scans can be useful in detecting tongue abnormalities. The procedure involves the patient lying still inside a machine, and at times, being asked to hold their breath to capture images of the body. Although it provides the most detailed images, MRI scans are the longest imaging technique, taking 15 to 90 minutes depending on the number of images needed. Some patients may find the enclosed space and loud noises of MRI scans distressing, but it is important to know that these are normal parts of the procedure and not dangerous.^2,4,5

Management and treatment of Hanhart syndrome

Management and treatment of Hanhart syndrome is not one-size-fits-all; instead, it  depends on a patient’s specific signs and symptoms. The severity of a patient’s signs and symptoms determine the urgency of management and treatment, with newborns sometimes requiring intensive care.^1,2

Surgery

Surgery can be performed to correct specific defects of Hanhart syndrome. When signs and symptoms of Hanhart syndrome cause problems with breathing, eating, feeding, and swallowing, surgery may be more urgently required to resolve these issues.²

Surgery may be particularly useful in correcting jaw deformities, with a range of techniques available depending on the specific issue.² Ultimately, there are various  surgeries available to correct the condition’s characteristic abnormalities, which can help a patient feel more comfortable in their appearance and physical ability. Consulting with a surgeon can help determine whether surgery is necessary and what the associated risks and benefits are.

Speech and language therapy

Some patients with Hanhart syndrome experience impaired speech.² Speech and language therapy can help resolve this issue. It involves a speech and language therapist working with a patient to plan a programme of sessions that aims to help the patient develop their speech and communication skills.

Occupational therapy

Completing day-to-day tasks may be more challenging for those with Hanhart syndrome due to a range of physical defects.² However, occupational therapy can help patients establish techniques to promote their participation in society and live more independently. Occupational therapy, led by an occupational therapist, often occurs over multiple sessions, identifying strategies for the patient to improve their function and  ways to adapt their environment to make it easier for them to engage with. Occupational therapists can collaborate with the patient’s family, teachers, and employers to create sustainable strategies for the patient.⁶

Prosthetics

Prosthetics are devices attached to the body to help people move, especially beneficial for those with missing limbs.¹² Prosthetics have been used to replace missing limbs in patients with Hanhart syndrome, helping patients to move more easily and perform tasks that they might otherwise be unable to do.⁷

FAQs

How common is Hanhart syndrome?

Hanhart syndrome is a rare condition.² It affects less than one in 20,000 children, with only 30 cases being reported in research on the condition between 1932 to 1991. The prevalence of the condition does not appear to differ between those assigned female at birth and those assigned male at birth. 

Is Hanhart syndrome a genetic condition?

While some suspect that Hanhart syndrome is a genetic condition, particularly because it presents at birth, a specific gene associated with the condition has not yet been discovered.^1,2

Can Hanhart syndrome be detected during pregnancy?

Ultrasound scans during pregnancy can detect abnormalities in a baby’s development, which may indicate the possibility of Hanhart syndrome. However, a definitive diagnosis of Hanhart syndrome is typically made after birth through a doctor’s inspection of the newborn and imaging techniques.^1,2,8

Are there any long-term complications associated with Hanhart syndrome?

Hanhart syndrome's characteristic abnormalities can significantly impact the ability to  carry out day-to-day tasks due to restricted movement. This can pose many challenges for patients throughout their lives. Furthermore, Hanhart syndrome has been associated with disorders of the heart.^1,2

Can Hanhart syndrome be prevented?

As the cause of Hanhart syndrome is not known, there are no established methods to prevent the condition. Nonetheless, genetic counselling is recommended for parents to provide them with information on the risk of their future child having a genetic disease.^1,2

Are there any risk factors for Hanhart syndrome?

Risk factors for Hanhart syndrome are not well established. However, some research suggests that children of close blood relatives are more vulnerable to the condition.

Summary

Hanhart syndrome is a rare disorder that manifests at birth, with an unknown cause. It is characterised by the absence or underdevelopment of the tongue and the absence or malformation of fingers or toes. Malformations in other parts of the body, especially the jaw and limbs, often accompany Hanhart syndrome’s characteristic abnormalities. 

The diagnosis can be made by simply inspecting a patient, though imaging techniques may be employed to confirm it. 

As signs and symptoms of Hanhart syndrome vary among patients, management and treatment can vary, and may include surgery, speech and language therapy, occupational therapy, and prosthetics.