| Abstract|| |
Achondroplasia is a genetic disorder that is due to mutation of fibroblast growth factor receptor (FGFR3) gene and it results in dwarfism. It is inherited as an autosomal dominant trait. The classical clinical features seen are disproportionate dwarfism, rhizomelic shortening (proximal limbs), short fingers and toes with trident hands, large head with prominent forehead (frontal bossing), small mid face with flattened nasal bridge, spinal kyphosis or lordosis, varus (bowleg), and valgus (knock knee) deformities. Oral findings include macroglossia, tongue thrust swallowing pattern, posterior crossbite, anterior open bite, anterior reverse overjet, etc., This case report present the features and oral treatment protocol for Achondroplasia.
Keywords: Achondroplasia, disproportionate dwarfism, kyphosis, mutation, rhizomelia
|How to cite this article:|
Swathi K V, Maragathavalli G. Achondroplasia: A form of disproportionate dwarfism - A case report. Indian J Dent Res 2020;31:794-8
|How to cite this URL:|
Swathi K V, Maragathavalli G. Achondroplasia: A form of disproportionate dwarfism - A case report. Indian J Dent Res [serial online] 2020 [cited 2021 Jan 18];31:794-8. Available from: https://www.ijdr.in/text.asp?2020/31/5/794/306447
| Introduction|| |
The word Achondroplasia comes from the Greek word meaning “without cartilage formation”. Cartilaginous tissues become bone during fetal development whereas in achondroplastic individuals, an anomalous process occurs during growth especially in the long bones. Achondroplasia is the most common form of skeletal dysplasia characterized by short limb dwarfism that affects the growth of spine, skull, and tubular bones. It is the most common form of rhizomelic dwarfism and is caused due to mutation of fibroblast growth factor receptor-3 (FGFR3). In Achondroplasia there is abnormality in endochondral ossification. Fibroblast growth factors are structurally related proteins associated with cell growth, migration, wound healing, and angiogenesis. The mutation of FGFR3 causes limitation of endochondral ossification. The FGFR3 is a negative regulator of the chondrocytes proliferation and differentiation in growth plate. The characteristic features of Achondroplasia include short stature, a relatively large head with frontal bossing and midface hypoplasia, rhizomelic shortening of the limbs, trident hands, muscular hypotonia, and thoraco-lumbar kyphosis. There is also mild discrepancy between the muscular development and skeleton and there is an excess of soft tissues compared to bone length. The abdomen has a mild convexity with lumbar hyperlordosis, compensated by a lower dorsal kyphosis. The joints have a large articular amplitude due to ligament laxity. This pattern is widespread in infants and adults at the knees (genu recurvatum). At the hoses of the elbows and hips, there is limited joint extension capability. The spinal canal is small due to the narrowness of the posterior vertebral arches and decrease of the space between pedicles where the spinal cord is located which may lead to spinal cord compression. The oral findings include macroglossia, tongue thrust swallowing pattern, posterior crossbite, anterior open bite, anterior reverse overjet. There is longitudinal growth arrest of the bone, remainder of the growth mechanism (spine formation, hypertrophy, calcification, and ossification) occurs normally but the amount of bone that is formed is significantly less in cases of Achondroplasia. The health problems commonly associated with Achondroplasia include episodes of apnea, obesity, and recurrent ear infections. In childhood, Achondroplastic individuals have a pronounced and permanent lordosis and bowed legs. Some individuals also develop kyphosis and back pain. A potentially serious complication of Achondroplasia is spinal stenosis, which is a narrowing of the spinal canal that can cause compression of the upper part of the spinal cord. Spinal stenosis is associated with pain, tingling, and weakness in the legs that can cause difficulty in walking. Another uncommon but serious complication of Achondroplasia is hydrocephalus, which is fluid buildup in the brain that can lead to increased head size and brain-related abnormalities. The diagnosis of Achondroplasia can be done before birth by using prenatal ultrasound wherein there is progressive discordance between femur length and biparietal diameter. DNA test can be done before birth for detection of homozygosity. A skeletal survey is required to confirm the diagnosis of Achondroplasia. The skull is large, skull base is relatively small with narrow foramen magnum. The vertebral bodies are short and flattened. The iliac wings are small and squared. The tubular bones are short and thick with metaphyseal cupping. Fibular overgrowth may be seen. There is no particular treatment for achondroplasia however usage of human growth hormone, limb lengthening, gene therapies have been tried to improve the quality of life in individuals affected with this disorder. This case reports the characteristic clinical findings and oral care rendered to the patient affected with this genetic disorder.
| Case Report|| |
A 50-year-old male patient reported with the chief complaint of missing teeth in the upper and lower jaw in the anterior tooth region and desired replacement for the same. He had progressive mobility of his teeth with subsequent loss of teeth leading to the present partially edentulous condition. He worked as a circus comedian to earn his livelihood. History revealed his sibling (sister) also has the same short physical features as him.
On extraoral examination, he was of short stature (disproportionate dwarfism), frontal bossing, depressed saddle shaped nose, hypertelorism, skeletal class III profile [Figure 1]. His hands and feet were trident, short and stubby [Figure 2].
|Figure 1: (a-c) Features suggestive of disproportionate rhizomelic shortening|
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On intraoral examination, soft tissue examination revealed areas of brownish black pigmentation with hyperkeratosis seen in relation to both right and left buccal mucosa suggestive of smokers' melanosis. The structure, color, and attachment were normal. The tongue was wide and large with respect to the jaws suggestive of macroglossia; however, tongue movements were normal [Figure 3]. He was partially edentulous in relation to 11, 12, 13, 15, 21, 22, 23, 25, 31, 32, 36, 41, 42, 46. The remaining teeth had tobacco stains and were also periodontally compromised. Presence of high arched palate and reverse overjet were also seen [Figure 4].
|Figure 3: (a and b): Smokers' melanosis seen in relation to right and left buccal mucosa|
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|Figure 4: (a): Features of alveolar atrophy. (b): Features of macroglossia|
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Orthopantomogram revealed multiple missing 11, 12, 13, 15, 21, 22, 23, 25, 31, 32, 36, 41, 42, 46. Generalised horizontal bone loss involving crestal and middle 1/3rd of alveolar bone seen. Lateral cephalogram revealed prognathic mandible and retrognathic maxilla with reverse overjet. There was increased upper facial height. Posteroanterior view of the skull revealed frontal bossing and mid face hypoplasia [Figure 5].
|Figure 5: (a): Orthopantomogram (OPG) revealed horizontal bone resorption involving crestal, middle 1/3rd of alveolar bone. (b): Lateral cephalogram revealed skeletal class III profile. (c): PA view of skull showed features of large prominent forehead (frontal bossing) and midface hypoplasia|
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The positive familial history, characteristic clinical and radiographic features suggest a most likely disorder of cartilage formation and is diagnosed as Achondroplasia. This patient was advised extraction of the remaining periodontally compromised teeth followed by removable prosthesis.
| Discussion|| |
The prevalence of Achondroplasia is approximately 1 in 20,000 livebirths. Patients with Achondroplasia have a gain-of-function mutation in the fibroblast growth factor receptor 3 gene and there are two specific mutations that occur in the same nucleotide in the FGFR3 gene i.e., 1138G > A (98%) and 1138G > C (1%) resulting in glycine-to-arginine substitution in amino acid 380 (p. Gly380Arg) in the transmembrane domain of the FGFR3 gene. This type of mutation activates the FGFR3 receptor which causes the inhibition of the proliferation of chondrocytes leading to an impaired endochondral bone formation, growth restriction, and other skeletal anomalies. In Achondroplasia, the quality of life can be affected through stigmatization mainly due to lack of self-esteem. Apart from that there are other comprehensive factors like scoliosis, kyphosis which can affect them to perform daily activities of life [Table 1]. Certain other complications like otitis media, respiratory difficulty, and spinal stenosis can also be associated. Hence, this physical and psychological elements can deter the overall quality of life in these individuals. Although the endochondral bone formation is affected in these patients, the intramembranous, and periosteal ossification is normal. Reconstructive surgery such as lower limb lengthening can be done to achieve the physiological proportions. The limb lengthening procedure had been termed as extensive limb lengthening (ELL). The benefits from ELL may be in terms of functional, psychosocial, and therapeutic conditions. The functional benefits include increase in stature. Psychological benefits include a complete change in body image. The rhizomelic pattern of dwarfism lends itself favorably to limb lengthening to restore a more normal body proportionality. Achondroplastic individuals have a normal joint structure, so the height gained from limb lengthening improves function as well as aesthetics. Achondroplastic patients show increased ligament and joint laxity, their muscle length exceeding bone length before lengthening. Thereby, the lengthening process can be facilitated by ELL. The trunk limbs and rhizomelic disproportions are less pronounced. ELL has some prophylactic and therapeutic benefits such as hyperlordosis reduction can reduce spinal stenosis; knee alignment can reduce the onset of arthritis, both on knee, and hip level, etc. In some cases of achondroplasia an additional feature of polydactyly can be seen which results from defective patterning of anterior–posterior axis of the limb during development. Achondroplastic children are at a high risk of persistent or recurrent otitis media which may lead to conductive hearing loss which may be linked to midface hypoplasia, shortened Eustachian tube More Detailss, small pharynx, and relative enlargement of the tonsils and adenoids. The treatment options for Achondroplasia may include support groups and growth hormone therapy. Adequate efforts should be taken to prevent complications such as obesity, hydrocephalus, obstructive sleep apnoea, middle ear infections, and spinal stenosis. Nutritional counseling like smaller meal portion sizes should be implemented early to help reduce the later effects of obesity in adult life. Cervical cord compression at the cervicomedullary junction is frequently observed radiographically in children with achondroplasia. Significant compression at the foramen magnum can lead to severe neurological complications such as sleep apnea, disordered respiration, myelopathy, hydrocephalus, and sudden infant death. Hydrocephalus, observed as ventriculomegaly and excessive extra-axial fluid should be evaluated by frequent monitoring of the occipital-frontal circumference (OFC) during the first 12 months of life by evaluating with specialized head circumference growth charts for children with achondroplasia. Surgical options like decompressive laminectomy may be used to treat spinal canal stenosis in individuals with achondroplasia. Due to the high prevalence of otitis media and hearing loss in this population, routine early hearing tests and referral for speech and language review for infants and young children with achondroplasia should be done to prevent these complications.
|Table 1: Summary of literature evidence of demographic data, clinical, radiographic findings, investigations and management of achondroplasia|
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| Conclusion|| |
Achondroplasia is a genetic disorder of absence of cartilage formation. The clinical and radiographic features of this case were characteristic of Achondroplasia. The incidence of Achondroplasia is 1 in 20,000 livebirths and most of the Achondroplastic individuals are professionally circus entertainers. The quality of life is affected as a result of physical manifestations due to musculoskeletal, neurological, cardiovascular, and respiratory complications as well as psychological aspects in these individuals can also be compensated, hence a multidisciplinary approach is required by periodic review with physiotherapist, early screening and recognition to address the physical complications and proper counseling and guidance through various social welfare organizations or support groups is necessary for improving the self-confidence and esteem for promoting their overall quality of life and well-being. Newer drug therapies like C-natriuretic peptide (CNP), which acts by antagonizing the downstream effects of the aberrant FGFR3 signal has been shown to normalize bone growth in rodent models of achondroplasia. This drug is currently under Phase II clinical trial and further scope and potential of this drug needs to be evaluated.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
We would like to thank the Department of Oral Medicine and Radiology, Saveetha Dental College for supporting us to perform radiographic and biochemical investigations pertaining to the case.
Financial support and sponsorship
Department of Oral Medicine and Radiology, Saveetha Dental College.
Conflicts of interest
There are no conflicts of interest.
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Dr. G Maragathavalli
Department of Oral Medicine and Radiology, Saveetha Dental College, No. 162, Poonamallee High Road, Chennai - 600 077, Tamil Nadu
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]