Introduction

Hanhart syndrome is a rare congenital genetic disorder. It belongs to the group of overlapping medical conditions, known as ‘Oromandibular Limb Hypogenesis syndrome (OLHS)’ characterised by developmental anomalies of the mouth, face and limbs.¹ The syndrome is called “Hanhart syndrome” as it was first described by Dr. Hanhart in the 1960s. It is categorised as a limb reduction type of condition because it primarily affects the limbs, but it also includes classic oral and facial defects.². Though the prevalence of Hanhart syndrome is low, it significantly affects the physical appearance and muscular movements of an individual with this condition. Individuals with this condition may have a combination of more than one symptom depending on the extent and severity. 

This article aims at understanding the oral and facial symptoms of Hanhart syndrome, its diagnosis, treatment and supportive care required by individuals suffering from the condition.

Notable figures

Nicholas (Nick) Santonastasso and Gabe Adams-Wheatley are famous internet sensations. Nick was born with only one arm and no legs, he is a bodybuilder and motivational speaker, Gabe was born with no hands or legs. He is an influencer and works across the world to help those with various disabilities and conditions.

Causes of hanhart syndrome

Though the exact cause and genes associated with the syndrome are not identified,⁷ it has been linked to multiple hypotheses:

• It has been reported in children of blood relatives (consanguinity) that may be inherited through autosomal recessive (two abnormal genes of the same trait, one from each parent) pattern¹
• Some scientists believe that the syndrome may manifest due to blood clots disrupting the blood flow to tissues and organs during formative stages leading to developmental abnormalities¹
• Exposure to drugs during pregnancy⁴

Oral and facial defects

Oral defects

• Smallmouth ⁸
• Small jaws 
• Abnormally receding jaw 
• Short, underdeveloped tongue 
• Cleft palate
• Narrow, high arched palate⁸
• Cleft tongue
• Partial absence of lower jaw teeth 

Facial defects

• Facial asymmetry
• Abnormal lower eyelids
• More than normal distance between the inner corners of the eyes 
• Broad nose
• Facial palsy
• Ear abnormalities
• Underdeveloped or incompletely developed nasal cartilage

Diagnostic approaches

A diagnosis of Hanhart syndrome involves physical examination, imaging, and genetic testing. 

The findings are reviewed by a team of geneticists, paediatricians, oral surgeons, orthodontists, plastic surgeons, etc. 

Implications

The orofacial defects if not treated result in a wide range of implications such as

• Feeding difficulties: In infants with oral defects, feeding poses a common problem affecting their nutrition. Planned surgical correction, feeding plans and prostheses can be helpful⁸
• Recurrent ear infections: If the facial structures are underdeveloped, they may result in underdeveloped ear anatomy, causing ear infections
• Poor speech: Small or underdeveloped tongue and lower jaw, abnormal and misaligned teeth or missing teeth all result in poor speech
• Difficulties in chewing: The oral defects affect the biting and chewing 
• Difficulties in swallowing: If the oral structures are underdeveloped to a greater extent, it may make swallowing difficult and painful
• Difficulties in vision: If the facial nerves are affected, there could be vision challenges
• Delayed eruption of teeth: It is a classic symptom of Hanhart syndrome 
• Crooked teeth: The position and structure of the jaws cause teeth to become crooked and misaligned
• Poor dental hygiene: Crowded and crooked teeth and absence or underdeveloped limbs. Missing fingers make oral hygiene maintenance difficult
• Gum infection: Poor oral hygiene results in bleeding and inflamed gums
• Dental cavities: Poor oral hygiene and crooked teeth increase the chances of dental cavities
• Psychological effects: Individuals with this condition face many psychological effects due to appearance and functional limitations
• Difficulty in breathing: If the orofacial structure is severely underdeveloped, it may lead to breathing problems

Management and treatment

Management and treatment of the clinical findings are based on the severity of the condition. Early intervention, counselling, surgical rehabilitation and continued supportive care are the standard approach. A multidisciplinary team of specialists including but not limited to paediatricians, oral surgeons, plastic surgeons, physical therapists, speech therapists, psychologists, and audiologists are involved in the treatment planning and management.¹¹

Infants with Hanhart syndrome may have feeding difficulties resulting from oral cavity defects. They could be surgically corrected and prosthetically rehabilitated to ensure proper nutrition.

Cleft lip and cleft palate require surgical correction. When diagnosed at an early age and corrected surgically, it improves feeding, speech and physical appearance. Jaw and teeth may be repositioned and realigned surgically to improve appearance, bite and speech. Children with Hanhart syndrome largely benefit from speech therapy.

FAQs

What is hanhart syndrome?

A rare condition present since birth presenting with developmental defects of the oral cavity, face and limbs.

What causes hanhart syndrome?

The cause of Hanhart syndrome is not fully understood. It occurs randomly and without any direct association. However, research suggests that it could be due to abnormal genes from both parents, due to certain drugs taken during pregnancy or to blood clots that resulted in inadequate blood supply to the organs and tissues during development in utero.

How common is hanhart syndrome?

Hanhart syndrome is classified as a rare medical condition. Due to its rarity, the exact prevalence might not be available, but currently, it is estimated to affect 1 in 1,000,000 live births worldwide.

Other names of hanhart syndrome?

Hypoglossia-hypodactylia syndrome (hypoglossia- small tongue, hypodactylia- absent or missing fingers and/or toes)

Summary 

Hanhart syndrome is a rare medical condition caused by genetic mutations and characterised by an abnormally developed or underdeveloped tongue, jaw, face, absent or partially missing fingers and/or toes, and malformed arms and/or legs. The exact cause and the gene mutation causing Hanhart syndrome are not known to date. The treatment and management of each case depends upon the extent of severity and usually involves a multidisciplinary approach. Early intervention, surgical rehabilitation and ongoing supportive care can significantly improve the outcomes and quality of life for individuals affected by Hanhart syndrome. The prognosis and outcome depend on the severity of an individual’s condition. Famous personalities with Hanhart syndrome have successfully overcome challenges associated with it through early intervention, counselling, and supportive care. Families of individuals with Hanhart syndrome benefit from counselling and therapy to navigate through these challenges together.