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The role of endoscopic third ventriculostomy in the treatment of triventricular hydrocephalus seen in children with achondroplasia.

The authors of this paper describe two patients with achondroplasia in whom triventricular hydrocephalus has been successfully treated using endoscopic third ventriculostomy (ETV). The authors performed ETVs in two children with achondroplasia involving a moderate macrocranium and enlarged lateral and third ventricles with intermittent clinical evidence of increased intracranial pressure. The endoscopic procedure revealed a significant deformation of the floor of the third ventricle in both patients caused by longstanding hydrocephalus. Because of the anatomical variations such as empty sella and the persistence of the infundibular recess, the ETV procedure became technically demanding. The standard ventriculostomy on the tuber cinereum was not possible. Ventriculostomies were performed on the part of the third ventricular floor that was hanging ventral to the pons. Both patients became symptom free postoperatively, and phase-contrast cine magnetic resonance (MR) imaging studies confirmed the patency and effectivity of the ventriculostomy sites. The authors suggest that ETVs may constitute an alternative for ventriculoperitoneal shunt therapy as the treatment of choice for patients with achondroplasia who have triventricular hydrocephalus and clinical symptoms. Attention should be paid to the shape of the floor of the third ventricle, however, especially in cases of longstanding hydrocephalus. An association of the empty sella or the persistence of the infundibular recess must be carefully evaluated using MR imaging studies before attempting ETVs in such patients.

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In utero analysis of heterozygous achondroplasia: variable time of onset as detected by femur length measurements.

Seven cases of heterozygous achondroplasia were examined in utero. Although the head shape and growth were normal, the initially normal femur length showed a decrease in growth and fell below the lower 99 per cent confidence limit in all cases. The time of presentation of achondroplasia varied between 21 and 27 gestational weeks. This study suggests that the diagnosis of achondroplasia can be reasonably made when the femur is abnormally short. When the femoral length is appropriate prior to 30 weeks, more caution should be taken in interpretation. Because of the variability in presentation, the fetus could be normal or still could be affected.

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[Gly380Arg and Asn540Lys mutations of fibroblast growth factor receptor 3 in achondroplasia and hypochndroplasia in the Spanish population].

BACKGROUND: Achondroplasia, the most common type of genetic dwarfism characterised by disproportionate short stature and other skeletal anomalies, results from a defect in the maturation of the chondrocytes in the growth plate cartilage. Hypochondroplasia, considered allelic to achondroplasia is clinically and genetically heterogeneous. Recent studies have mapped the gene on chromosome 4p16.3, and frequent mutations in the fibroblast growth factor 3 (FGFR3) have been described in these diseases in other populations. PATIENTS AND METHODS: Analysis of the FGFR3 gene mutations Gly380Arg and Asn540Lys in 20 Spanish patients (10 achondroplasic, 6 hypochondroplasic and 4 with skeletal dysplasias with some phenotypic and radiological characteristics of hypochondroplasia) by PCR and restriction analysis. RESULTS: All the achondroplasic patients have shown the same mutation (Gly380Arg) in the transmembrane domain of the receptor. Five hypochondroplasic patients presented the mutation Asn540Lys in the proximal thirosine kinase domain. CONCLUSIONS: Achondroplasia in this sample from Spanish patients is also homogeneous in its molecular basis. Genetic heterogeneity has been found in hypochondroplasia corresponding with the phenotypic diversity in this disease. Molecular analysis of FGFR3 may be an additional diagnostic tool and facilitates genetic counselling in these chondrodysplasias.

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[Fibroblast growth factor receptor and achondroplasia].

Fibroblast growth factor receptor 3 (FGFR3) has been establishing its position in growth plate cartilage after the identification as a responsible gene for achondroplasia. The major pathway of the pathogenesis in achondroplasia is the suppression of parathyroid hormone-related protein (PTHrP)-parathyroid hormone receptor (PTHR) system, which is mainly mediated by extracellular signal regulated kinase (ERK) activation induced by constitutive active FGFR3. However, intracellular signaling system in FGFR3 is complex and the molecular pathogenesis of achondroplasia and related disorders has not been fully clarified. In this review, I summarized recent consensus in the pathogenesis of FGFR3 related chondrodysplasia.

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A clinical observation of achondroplasia.

Twenty-five cases of achondroplasia followed for a period of recent three years are reviewed. There were 17 males and 8 females. Twelve cases (48%) visited us before one-year-old. Familial vertical transmissions were noted in only three patients (12%) and others were new mutations. Patients usually had typical rhizomelic short stature, large head, frontal bossing and trident fingers. Their heights were around four standard deviations below the 50th percentile of the normal growth curve. The head girths of several patients were above the 97th percentile of the normal growth curve, but were normal in a special growth chart for achondroplasia. No mental problem was noted in our patients. Three of the seven patients older than five years had severe leg bowing and kyphosis, and the oldest one (17-years-old) had nerve compression symptoms. Genetic counselling and the management of complications in achondroplasia are important.

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[A case report on the achondroplasia and its dental findings].

Achondroplasia is characterized by an undergrowth of arms and legs bones, low height and undergrowth of the Basis cranil. The name of this disease was called Chondrodystrohia foetalis before Parrot reported the name of this disease as Achondroplasia, distinguished from other similar diseases. We are reporting in this paper on an 11-year, 2-month-old girl with Achondroplasia. The dental findings as follows: 1) Open bite was observed for the front teeth. 2) The size, number, form and growth of the teeth were usual. 3) The tongue was a little bigger than usual. 4) According to X-ray cephalometric analysis, undergrowth of the Basis cranii and relative anterior cross-bite were visible.

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Levels of creatine kinase activity in cartilage of tubular and nontubular bone in relation to pathogenesis of achondroplasia.

For the purpose of investigating events of energy metabolism in growing cartilages of human tubular and nontubular bones, measurements of creatine kinase (CK), lactate dehydrogenase (LDH), and aldolase of freshly excised cartilages in normal and pathologic conditions were performed. The level of cartilage CK of the normal phalanges (tubular bone) and exostosis was significantly less than those of the normal iliac bones (nontubular bone) and the achondroplasia tubular bone. A similar difference was also found between the tubular and the nontubular bone of an autopsy subject with achondroplasia. There was no statistical difference in the levels of LDH and aldolase in the cartilage between the tubular and the nontubular bone. These observations together with results obtained from iliac and limb cartilages of the newborn rat suggest the hypothesis that CK activity of cartilage of the tubular and the nontubular bone is different; cartilage of achondroplasia tubular bone has CK activity similar to that of normal nontubular bone cartilage.

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[Compression of the cervical spinal cord in achondroplasia].

Two cases of tetraparesis due to cervico-occipital spinal cord compression in infants with achondroplasia are reported. Neurological disorders in achondroplasia are produced by structural anomalies of the cranium and spinal canal. They can be divided into two categories: hydrocephalus and radicular and spinal cord compression syndromes. Cervico-occipital compression is more frequent in childhood and may occur very early, in the first months of life. Early diagnosis of this complication and anatomic evaluation can now be obtained by computed tomography, which shows the exact dimensions of the foramen magnum, and myelography. Achondroplasia requires very close neurologic monitoring and, when findings are abnormal, radiologic investigations of the cervico-occipital zone. This allows for early surgical management which is the only means of obtaining significant therapeutic results.

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Prevention of fixed, angular kyphosis in achondroplasia.

Transient kyphotic deformity arises in most infants with achondroplasia. In a minority, a fixed and angular kyphosis develops, which can cause serious neurologic sequelae later in life. We assessed a protocol for preventing development of such fixed kyphosis in a sequential, unselected series of 66 infants with achondroplasia. This study demonstrates the efficacy of early prohibition of unsupported sitting and, in those in whom such prohibition proves insufficient, use of bracing. When the proposed algorithm was followed, none of the infants had development of a progressive kyphotic deformity. On this basis, it appears that the secondary risks of angular kyphosis, previously estimated to be between 10 and 15% in individuals with achondroplasia, can be completely eliminated.

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Human growth hormone treatment in prepubertal children with achondroplasia.

We studied the effects of recombinant human growth hormone (GH) treatment in 6 prepubertal children with achondroplasia. The patients' age ranged from 2 11/12 to 8 5/12 years and the GH dose was of 0.1 IU/kg/day subcutaneously. Auxological assessments and bone age determinations were performed 6 months before, at the beginning, and after 6 and 12 months of therapy. The growth velocity increase during the whole year of treatment ranged from 1.1 to 2.6 cm/year in 3 patients while in the others no variation was detected. No side effects were observed during the trial apart from a slight advancement of bone age in two patients. MRI at the cervicomedullary junction and CT scan of the base of the skull did not show any variation of the dimensions of the foramen magnum at the end of the trial compared to baseline. Our study shows that r-hGH can safely increase short-term growth velocity in some but not all prepubertal children with achondroplasia. Our data confirm the individual variability in the response to the GH treatment.

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Standard weight for height curves in achondroplasia.

Standard curves developed for the general population cannot be used to assess the growth of an individual who has a condition that results in disproportionate short stature. For this reason, efforts have been made to develop growth curves specific for several of the chondrodysplasias. However, data concerning weight for height have been largely lacking, although they may be of particular importance for conditions such as achondroplasia, where there is some consensus that an increased prevalence of obesity is a particular problem. In this paper we provide standard weight for height curves for males and females with achondroplasia, and discuss the use of several indices which have been applied to the assessment of body fat in the general population.

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An improved methodology for the detection of the common mutation in the FGFR3 gene responsible for achondroplasia.

Homozygous achondroplasia is a neonatal lethal condition which can only be diagnosed in the first trimester of pregnancy by molecular analysis. The vast majority of patients with achondroplasia have a G-->A substitution at position 1138 of the fibroblast growth factor receptor (FGFR3) cDNA sequence, resulting in the substitution of an arginine for a glycine residue at position 380 of the FGFR3 protein. This mutation has typically been detected by SfcI digestion of amplified genomic DNA. We have demonstrated that the SfcI digestion protocol does not consistently distinguish between DNA samples heterozygous and homozygous for the G1138A substitution, and illustrates how the misdiagnosis of a homozygous affected fetus for one carrying only one copy of the G1138A mutation could occur. We report here an improved, simple nonradioactive technique which can reliably and consistently detect the presence of the G1138A mutation both in the heterozygous and homozygous state.

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Occurrence of thanatophoric dysplasia type I (R248C) and hypochondroplasia (N540K) mutations in two patients with achondroplasia phenotype.

We report two patients with clinical and radiological findings of achondroplasia, who had the most common FGFR3 mutation occurring in thanatophoric dysplasia type I and hypochondroplasia, respectively. Thanatophoric dysplasia is usually a lethal condition, but the patient carrying this mutation is alive and presents a medical history similar to that of patients with achondroplasia. The events leading to such a discrepancy between genotype and phenotype are unclear. These rare cases may influence an appropriate medical and genetic counseling.

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Absence of correlation between infantile hypotonia and foramen magnum size in achondroplasia.

Virtually all infants with achondroplasia exhibit variably severe hypotonia in infancy. This hypotonia contributes to delays in motor development and risks for sudden death. Some have proposed that this hypotonia is a direct result of impaired function of long tracts of the spinal cord, secondary to the intrinsic narrowing of the foramen magnum, which also is present in variable severity in all children with achondroplasia. We postulated that if foraminal constriction causes infantile hypotonia, then there should be a strongly positive correlation between foraminal size and severity of hypotonia. Therefore, clinical and computed tomographic data in 71 infants were retrospectively reviewed. We found no correlation. These results suggest that there is no direct relationship and foraminal size does not affect severity of hypotonia. Other potential explanations for this infantile hypotonia are considered.

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Achondroplasia-hypochondroplasia complex.

We report on a 14-year-old girl with the achondroplasia-hypochondroplasia complex. This patient has been reported previously [McKusick et al, 1973], and we offer an update on her condition. The patient has clinical features different from both achondroplasia and hypochondroplasia and is mentally retarded. Radiological changes, which have occurred over 14 years, are included.

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Genetic counselling in unexpected familial recurrence of achondroplasia.

Two additional pedigrees with familial recurrence of achondroplasia are described. Genetic risk for children of sibs of affected individuals or premutation carriers seems to be low, but it is advisable to monitor at risk pregnancies by midtrimester ultrasonography to diagnose fetal achondroplasia.

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Obesity in achondroplasia.

Obesity is a significant and potentially serious health problem in achondroplasia. Body mass indices, weight-to-square of the height ratio (W/H2), and triceps skinfold measurements show that obesity is common. It begins in early childhood and is prevalent at all ages. We recommend that weight be monitored closely in all persons with achondroplasia and that dietary intervention be instituted whenever the body mass indices, W/H2, and triceps skinfold measurements exceed the 95th centile for the general population.

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Growth of the foramen magnum in achondroplasia.

Foramen magnum growth curves in achondroplasia and in the general population are presented. The achondroplastic foramen magnum is small at birth, and during the first year it has a severely impaired rate of growth especially in the transverse dimension. This markedly diminished growth results not only from abnormal endochondral bone growth but also because of abnormal placement and premature fusion of the synchondroses. Evaluation of the foramen magnum in achondroplasia should address absolute size of the transverse and sagittal dimensions, shape, and growth centers to determine growth potential of this area.

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