1/53. hypophosphatasia. review of 24 cases.Radiographic analysis of 24 cases of hypophosphatasia (H) from 9 Paediatric Centres was performed. 3 cases were of neonatal (lethal), 18 cases of infantile (severe) and 3 cases of late (benign) type. Some of the patients were in reality borderline cases between these groups. In the authors' material all the patients showed radiographic signs of the disease. These were divided into diagnostic, characteristic and suggestive features. All of the patients had in common generalised (usually irregular) osteoporosis, generalised (usually irregular) metaphyseal changes, craniostenosis (13 of 18 infantile cases) or widened cranial sutures and ofter bowing of the long bones. Besides the well know radiographic features of hypophosphatasia some less well known, rare or 'new' ones such as, 1. spurs of the long bones (Bowdler sign), 2. distal femoral central metaphyseal defects and epiphyseal defects, 3. S-like deformities of the tibiae, 4. abnormal shape of the distal phalanges of the fingers, 5. multiple rib fractures and slender bones, 6. wedging of the lower thoracic and upper lumbar vertebrae, 7. partial premature fusion of the epiphyses, 8. nephrocalcinosis, 9. loss of lamina dura around the teeth, 10. variation in radiographic appearances of a pair of siblings with lethal form, and, 11. rapid changes in roentgen appearances. are discussed. In two of our patients (siblings) phosphoethanolamine was undetectable in the urine. The authors doubt if a normal skeletal survey may be present at any stage in any of the three major types of hypophosphatasia.- - - - - - - - - - ranking = 1keywords = bone (Clic here for more details about this article) |
2/53. Mild hypophosphatasia mimicking severe osteogenesis imperfecta in utero: bent but not broken.We describe a fifth instance of hypophosphatasia presenting with prenatal findings suggestive of a very severe bone dysplasia but with a subsequently benign course. Spontaneous improvement of long-bone angulation began prenatally. The postnatal course has been encouraging. This sixth clinical form of hypophosphatasia, which we suggest should be called the benign prenatal form of hypophosphatasia, should be added to the differential diagnostic possibilities considered when angulation or bowing of long bones is discovered prenatally.- - - - - - - - - - ranking = 1keywords = bone (Clic here for more details about this article) |
3/53. hypophosphatasia: the importance of alkaline phosphatase in bone mineralization.The authors describe a neonate who was diagnosed with "perinatal hypophosphatasia". The clinical manifestations in this patient were small head size, soft calvarium (caput membranaceum), and short bowing forearms and legs. Laboratory investigations revealed hypercalcemia at 12.7 mg/dl, hyperphosphatemia 8.6 mg/dl, and extremely low alkaline phosphatase 0 unit/L. Roentgenographic studies of the skull showed calcification only at frontal bone and base of the skull. Spines were small and flattened. Long bones were hypomineralized and deformed. The functions of alkaline phosphatase to bone development and mineralization were reviewed. Because perinatal hypophosphatasia is a fatal condition and inherited as an autosomal recessive pattern, prenatal diagnosis is necessary. The most reliable and suitable method in our facility is serial ultrasonography from which the diagnosis can be made by the second trimester.- - - - - - - - - - ranking = 2.3333333333333keywords = bone (Clic here for more details about this article) |
4/53. Asp361Val Mutant of alkaline phosphatase found in patients with dominantly inherited hypophosphatasia inhibits the activity of the wild-type enzyme.hypophosphatasia is characterized by the hypomineralization of bone associated with the mutation of the tissue-nonspecific alkaline phosphatase (TNSALP) gene. Although the disease is usually autosomal recessive, an autosomal dominant form is also recognized. Approximately 50 mutations have been found in the TNSALP gene in patients with hypophosphatasia. However, the mutations identified to date do not seem to account for the dominantly inherited form of the disease. We have examined a German family in which the father and all 4 children were affected with hypophosphatasia, whereas the mother was healthy. The affected members of this family showed premature loss of deciduous teeth at or shortly before 2 yr of age and low levels of serum ALP with elevated levels of urinary phosphoethanolamine. dna analysis by direct sequencing revealed a heterozygous missense mutation that caused the conversion of amino acid Asp to Val at position 361 (D361V) in the patients. Another substitution was detected in exon 12 (Val to Ala conversion at codon 505: V505A) in 1 allele of the mother and 3 children, indicating no association of the substitution with the disease. Reconstruction experiments demonstrated that the D361V mutant protein lost its enzymatic activity and that it inhibited the function of wild-type enzyme when coexpressed in COS-7 cells. On the other hand, the V505A mutant exhibited enzymatic activities equal to those of the wild-type ALP. It is likely that the mutant D361V protein forms dimers with the wild-type protein, and the protein-protein interaction contributes to the dominant effect of the mutant D361V. The mutation that causes D361V is the first one proven to be associated with the dominant form of hypophosphatasia.- - - - - - - - - - ranking = 0.33333333333333keywords = bone (Clic here for more details about this article) |
5/53. A molecular approach to dominance in hypophosphatasia.hypophosphatasia is an inherited disorder characterized by defective bone mineralization and a deficiency of tissue-nonspecific alkaline phosphatase (TNSALP) activity. The disease is highly variable in its clinical expression, because of various mutations in the TNSALP gene. In approximately 14% of the patients tested in our laboratory, only one TNSALP gene mutation was found, despite exhaustive sequencing of the gene, suggesting that missing mutations are harbored in intron or regulatory sequences or that the disease is dominantly transmitted. The distinction between these two situations is of importance, especially in terms of genetic counseling, but dominance is sometimes difficult to conclusively determine by using familial analysis since expression of the disease may be highly variable, with parents of even severely affected children showing no or extremely mild symptoms of the disease. We report here the study of eight point mutations (G46 V, A99T, S164L, R167 W, R206 W, G232 V, N461I, I473F) found in patients with no other detectable mutation. Three of these mutations, G46 V, S164L, and I473F, have not previously been described. pedigree and/or serum alkaline phosphatase data suggested possible dominant transmission in families with A99T, R167 W, and G232 V. By means of site-directed mutagenesis, transfections in COS-1 cells, and three-dimensional (3D) modeling, we evaluated the possible dominant effect of these eight mutations. The results showed that four of these mutations (G46 V, A99T, R167 W, and N461I) exhibited a negative dominant effect by inhibiting the enzymatic activity of the heterodimer, whereas the four others did not show such inhibition. Strong inhibition resulted in severe hypophosphatasia, whereas partial inhibition resulted in milder forms of the disease. Analysis of the 3D model of the enzyme showed that mutations exhibiting a dominant effect were clustered in two regions, viz., the active site and an area probably interacting with a region having a particular biological function such as dimerization, tetramerization, or membrane anchoring.- - - - - - - - - - ranking = 0.33333333333333keywords = bone (Clic here for more details about this article) |
6/53. Perinatal hypophosphatasia: radiology, pathology and molecular biology studies in a family harboring a splicing mutation (648 1A) and a novel missense mutation (N400S) in the tissue-nonspecific alkaline phosphatase (TNSALP) gene.We report on a postmortem diagnosis of perinatal lethal hypophosphatasia, an inborn error of metabolism characterized by a liver/bone/kidney alkaline phosphatase (ALP)-related defective bone mineralization due to mutations in the tissue-nonspecific alkaline phosphatase (TNSALP) gene. Radiological and pathological studies identified a perinatal lethal hypophosphatasia showing a generalized bone mineralization defect including asymmetry of the cervical vertebral arches in a 22 4 weeks' gestation fetus. Both parents revealed low serum ALP activities supporting the diagnosis. Sequencing analysis of the TNSALP gene showed two heterozygous mutations, 648 1A, a mutation affecting the donor splice site in exon 6, and N400S, a novel missense mutation in exon 11, located near the active site and very close to histidins 364 and 437, two crucial residues of the active site. Sequencing of exons 6 and 11 in the parents showed that 648 1A was from maternal origin and N400S from paternal origin. dna-based prenatal testing in the subsequent pregnancy following a chorionic villous sampling performed at 10 weeks of gestation showed no mutation and a healthy infant was born at term.- - - - - - - - - - ranking = 1keywords = bone (Clic here for more details about this article) |
7/53. hypophosphatasia-study on two autopsy cases.The autopsy findings of two cases of infantile hypophosphatasia are described and compared with those of 16 previously reported cases. Histochemical and biochemical tissue analysis for alkaline phosphatase showed a marked decrease in activity in liver, kidney, and bones. However, intestinal alkaline phosphatase possessed normal or slightly elevated activity. nephrocalcinosis is a frequent complication and its development depends on hypercalcemia and length of survival of the patient. Electron microscopic findings are illustrated, and a mechanism for the development of nephrocalcinosis is proposed. For the first time, marked elevations of parathyroid hormone was detected. This finding, coupled with the extreme difficulty in locating the parathyroid glands in cases of hypophosphatasia, is enigmatic. Areas for furture investigation are suggested.- - - - - - - - - - ranking = 0.33333333333333keywords = bone (Clic here for more details about this article) |
8/53. pyridoxine-dependent seizures associated with hypophosphatasia in a newborn.pyridoxine dependency and congenital hypophosphatasia are unusual metabolic disorders. We report a female infant born from healthy consanguineous parents with shortening of limbs, detected during pregnancy by ultrasonography. Immediately after delivery, the baby was admitted to the neonatal intensive care unit because of respiratory distress. A bone radiograph showed hypomineralization of all bones, and serum alkaline phosphatase was very low (10 U/L). Within the first day of life, seizures (focal clonic and tonic) started. The seizures were refractory to phenobarbital and other antiepileptic drugs. The first electroencephalogram (EEG) showed a burst-suppression pattern. pyridoxine was administered (50 mg/kg) and completely controlled the seizures. Antiepileptic drugs were discontinued, and a maintenance dose of pyridoxine (10 mg/day) was established. A postpyridoxine EEG revealed the disappearance of the burst-suppression pattern. The patient died at age 26 days. pyridoxine-dependent seizures, when recognized early and treated, have a more favorable prognosis. However, hypophosphatasia detected at birth almost always has a lethal outcome.- - - - - - - - - - ranking = 0.66666666666667keywords = bone (Clic here for more details about this article) |
9/53. hypophosphatasia associated with increased nuchal translucency: a report of two affected pregnancies.Perinatal hypophosphatasia is a lethal autosomal recessive skeletal abnormality with a birth prevalence of about 1 per 100 000. It is characterized by deficiency of the tissue-nonspecific isoenzyme of alkaline phosphatase causing abnormal bone mineralization. In the two affected fetuses from the same family ultrasound examination at 14 and 12 weeks, respectively, demonstrated increased nuchal translucency thickness, hypomineralization of the skull and spine, narrowing of the chest and shortening of the limbs.- - - - - - - - - - ranking = 0.33333333333333keywords = bone (Clic here for more details about this article) |
10/53. Severe hypophosphatasia due to mutations in the tissue-nonspecific alkaline phosphatase (TNSALP) gene.hypophosphatasia is a rare autosomal recessive inborn error of metabolism characterized by a defective bone mineralisation and deficiency of serum and tissue liver/bone/kidney alkaline phosphatase activity. We report the characterisation of tissue-nonspecific alkaline phosphatase (TNSALP) gene mutation in a patient affected by infantile hypophosphatasia. This boy was the first child of non affected, non related parents. At 1 month of age he presented with palsy of the left upper limb with hypotonia. Length was - 2SD. The anterior fontanel was large. There was a markedly decreased ossification of all bones. All limbs were shortened. Ultrasonographic examination of the kidneys showed nephrocalcinosis. Level of alkaline phosphatases was decreased in the child as well as in the parents. bone density was decreased. At 2 years of age development was delayed. Weight was - 3,5 SD and OFC - 3SD. The child had craniosynostosis. Molecular studies showed 2 missense mutations, both in exon 6 of the TNSALP gene.- - - - - - - - - - ranking = 1keywords = bone (Clic here for more details about this article) |
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