Introduction
Hanhart syndrome is a rare congenital disorder characterised by an underdeveloped tongue, malformed arms or legs extremities, and missing/shortened fingers or toes and jaw abnormalities. These craniofacial issues can worsen feeding difficulties.1
Hanhart syndrome may be associated with splenogonadal fusion, unilateral renal agenesis, and porencephalic cysts in the brain. Complications include severe physical deformities, intellectual disability, speech impairment, feeding difficulties, and infant death.2
Incidence and prevalence: In a study a researcher mentioned, a patient suffering from palmoplantar keratodermas led to Hanhart syndrome, which was caused by a tyrosine aminotransferase (enzyme) deficiency. The researcher suggested that Hanhart syndrome should be diagnosed early before it leads to major deformation and mental retardation.3
Viglizzo et al. 2006, reported a 2-year-old girl with an incomplete form of Hanhart syndrome, initially presenting with vesicles on her fingertips. These lesions developed into hyperkeratotic plaques on her palms and soles. She experienced photophobia and frequent tearing but had no intellectual impairment. Elevated serum and urine tyrosine levels confirmed the diagnosis. Early diagnosis is crucial to prevent the risk of mental abnormalities.4
In another report, Das et al. 2018, reported an 18-year-old boy with a 13-year history of speech problems. There was no family history of similar conditions, though a history of consanguineous marriage was noted. The patient had limb anomalies but could manage daily activities. Oral examination showed micrognathia, retrognathia, a deep palatal arch, a small tongue with limited mobility, tongue tie, and no chin contour. Investigations, including blood tests and radiology, were normal, but the orthopantomogram (OPG) showed missing teeth and malocclusion. He was diagnosed with Hanhart syndrome based on features like ocular hypertelorism, cleft palate, and conical teeth, with no neurological issue.2
Clinical presentation of deformities
The diagnosis is based on sixth and seventh cranial nerve palsies, which are often incomplete and affect both sides. The sixth nerve palsy results in loss of eye abduction and esotropia, while the seventh nerve palsy leads to facial nerve paralysis, there is no sagging of facial tissue. The lack of facial nerve function gives the characteristics of a mask-like appearance.5
Characteristics like facial features and lack of smiling in response to familiar stimuli confirm the diagnosis later. Systemic abnormalities, especially involving the cranial nerves, can lead to issues with nutrition and speech development. Craniofacial abnormalities can affect oral function and facial structure. Ocular symptoms are diverse, with esotropia being the most common, due to poor function of the lateral rectus muscles. This may result in a face turn or large-angle esotropia, with deviations.5
Treatment and management; surgical
Non-surgical treatment involves detecting and treating amblyopia, corneal exposure, and refractive errors. Minimization of ocular suppression and correcting strabismus surgically gives the patient the best chance of developing low-grade binocular vision.5
The management of Hanhart syndrome is complex and requires individualised surgical approaches, as no single procedure works for all patients. Success depends on realistic expectations, with optimal alignment often achieved only in the primary gaze, while esotropia may persist in the lateral gaze. Pre-surgical testing (forced duction) is crucial to determine if there is a tight medial rectus muscle. If the medial rectus (MR) is tight, simply transporting the vertical rectus muscle may not suffice. A staged approach is used, starting with vertical rectus transposition followed by medial rectal weakening if needed. Standard medial rectus transposition recession alone is rarely effective due to lack of abduction and MR contracture. In large-angle esotropia, significant MR recession may be required after initial surgery.5
In cooperative older patients, staged surgery can be avoided by using an adjustable surgical technique. A recent report on 10 adjustable vertical rectus transpositions in adults highlighted its benefits, and the ability to fine-tune the abducting effect and correct vertical strabismus from asymmetric transpositions. This approach can also be applied to the medial rectus muscle for postoperative adjustment of recession. However, due to the typically young age of most patients, adjustable techniques are often not feasible.5
Post-operative care and rehabilitation
Fanny et al. 2017 mentioned in their research a no-animal protein diet was initiated with amino acids, vitamins, and trace element supplements. Tyrosinemia levels dropped fourfold in 8 days, and cutaneous and ocular lesions resolved within 1 month.6
The treatment of Hanhart syndrome requires a team of specialists, including paediatricians, surgeons, dental experts, speech pathologists, and physical therapists. In infants, feeding difficulties caused by mouth and jaw malformations must be addressed promptly through surgery, prosthetics, or therapy to ensure proper growth. Speech therapy can help with speech difficulties; limb abnormalities may require treatment to improve motor skills, walking, and writing. Treatment is generally supportive and based on the individual's condition. Facial corrections may involve procedures such as reduction rhinoplasty and jaw surgery. The long-term prognosis depends on the severity of the symptoms.2
Hanhart syndrome can be detected before birth through ultrasound, making prenatal screening essential in consanguineous marriages to reduce complications. Early detection allows for timely intervention. Limb and craniofacial abnormalities may be treated with surgery or prosthetics, and affected children may require speech, physical, and occupational therapy.2
Complications
The syndrome affects all aspects of strabismus surgery. Preoperative evaluation is complicated by factors like epicanthic folds and lack of cooperation.5
During surgery, anesthesiologists may face challenges from increased oral secretions and craniofacial abnormalities, complicating intubation, and the surgical field. Surgeons may encounter unexpected muscle abnormalities, such as hypoplasia or fibrous bands, which, while not altering the surgical plan, increase the difficulty of the procedure.5
Summary
Hanhart syndrome is a rare congenital disorder marked by underdeveloped tongues, malformed extremities, and jaw abnormalities, which can lead to feeding difficulties and other complications. Associated conditions include splenogonadal fusion and brain cysts. Diagnosis is often based on physical features and cranial nerve palsies.
Case studies reveal varying manifestations, from 2 years old with skin lesions and elevated tyrosine level to an 18-year-old with limb anomalies and speech issues. Diagnosis often involves assessing facial and oral abnormalities, while treatment requires individualized surgical and supportive care. Early detection through prenatal screening and tailored interventions is crucial for managing symptoms and improving outcomes. Complications in surgery include challenges with anaesthesia and unexpected muscle abnormalities.
References
- Varal IG, Dogan P. Hanhart syndrome: hypoglossia-hypodactylia syndrome. Pan African Medical Journal. 2019;32(1).
- Das S, Mazumdar A, Maity BC, Ghose S. Hanhart syndrome: A rare case report and review of literature. Indian Journal of Case Reports. 2019;5(1):53-5.
- Boularbah S, Douhi Z, Oujdi S, Soughi M, Elloudi S, Baybay H, et al. Richner-Hanhart syndrome. CME. 2023;2(3):1.
- Viglizzo GM, Occella C, Bleidl D, Rongioletti F. Richner–Hanhart syndrome (tyrosinemia II): early diagnosis of an incomplete presentation with unusual findings. Pediatric dermatology. 2006;23(3):259-61.
- Laby DM. Moebius syndrome. Clinical Strabismus Management, Principles and Surgical Techniques: WB Saunders, Philadelphia, PA; 1999. p. 358-62.
- Locatelli F, Puzenat E, Arnoux JB, Blanc D, Aubin F. Richner-Hanhart syndrome (tyrosinemia type II). Cutis. 2017;100(6):E20-E2.
