1/52. Severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN): phenotypic analysis of a new skeletal dysplasia caused by a Lys650Met mutation in fibroblast growth factor receptor 3.We previously discovered a novel missense mutation (Lys650Met) in the tyrosine kinase domain of the fibroblast growth factor receptor 3 (FGFR3) gene in four unrelated individuals with a condition we called "severe achondroplasia with developmental delay and acanthosis nigricans" (SADDAN) [Tavormina et al., 1999: Am. J. Hum. Genet. 64:722-731]. Here we present a more detailed clinical account of the SADDAN phenotype. The FGFR3 Lys650Met mutation results in severe disturbances in endochondral bone growth that approach and overlap those observed in thanatophoric dysplasia, type I. However, this mutation is most often compatible with survival into adulthood. Other unusual bone deformities, such as femoral bowing with reverse (i.e., posterior apex) tibial and fibular bowing and "ram's horn" bowing of the clavicle, are also seen in some patients. In addition to skeletal dysplasia, progressive acanthosis nigricans, and central nervous system structural anomalies, seizures and severe developmental delays are observed in surviving SADDAN patients. Despite its location within the same FGFR3 codon as the thanatophoric dysplasia type II mutation (Lys650Glu) and a similar effect on constitutive activation of the FGFR3 tyrosine kinase, the Lys650Met is not associated with cloverleaf skull or craniosynostosis.- - - - - - - - - - ranking = 1keywords = receptor (Clic here for more details about this article) |
2/52. Insulin receptor antibodies and insulin resistance.The presence of insulin receptor antibodies is a rare cause of insulin resistance. patients usually have a combination of hyperglycemia, insulin resistance, acanthosis nigricans, and autoimmune features. We report a patient with systemic lupus erythematosus and severe insulin resistance due to insulin receptor antibodies. The most striking aspect of the clinical presentation is the resistance to insulin therapy, with our patient unresponsive to doses of up to 154,075 units in a day. While on a low-dose glucocorticoid therapy, the patient had clinical improvement, and glucose levels subsequently became normal even without insulin and glucocorticoid.- - - - - - - - - - ranking = 1.2keywords = receptor (Clic here for more details about this article) |
3/52. A gene for congenital generalized lipodystrophy maps to human chromosome 9q34.Congenital generalized lipodystrophy (CGL, Berardinelli-Seip syndrome, OMIM # 269700) is a rare autosomal recessive disorder characterized by near complete absence of adipose tissue from birth. Affected individuals have marked insulin resistance, hypertriglyceridemia and acanthosis nigricans, and develop diabetes mellitus during teenage years. The genetic defect for CGL is unknown. A semi-automated genome-wide scan with a set of highly polymorphic short tandem repeats (STR) was carried out in 17 well-characterized pedigrees and identified a locus for CGL to chromosome 9q34. The maximum two-point lod score obtained was 3.6 at D9S1818 (theta(max) = 0.05). There was evidence for genetic heterogeneity (alpha = 0.73) and 2 of the pedigrees were unlinked. Multipoint linkage analysis excluding the 2 unlinked families yielded a peak lod score of 5.4 between loci D9S1818 and D9S1826. The CGL1 critical region harbors a plausible candidate gene encoding the retinoid x receptor alpha (RXRA) that plays a central role in adipocyte differentiation. Identification of the CGL gene(s) will contribute to our understanding of the adipocyte differentiation and elucidation of the mechanisms of insulin resistance in disorders of adipose tissue.- - - - - - - - - - ranking = 0.2keywords = receptor (Clic here for more details about this article) |
4/52. insulin resistance and acanthosis nigricans. Report of a case with antibodies to insulin receptors.A 64-year-old black man presented with the syndrome of acanthosis nigricans and insulin-resistant diabetes mellitus requiring up to 3000 units of insulin per day. The patient's plasma contained circulating antibodies to insulin receptors thought to be responsible for the insulin resistance. The marked insulin resistance, the manifestations of acanthosis nigricans, the evidence of immunologic dysfunction by the absence of expected circulating antibodies to insulin, and the demonstration of circulating antibodies to insulin receptors put this patient in Kahn's category B of insulin resistance and acanthosis nigricans. There was no evidence of malignancy, lipodystrophy, or endocrine abnormality. The occurrence of acanthosis nigricans with insulin resistance due to binding of cell membrane insulin receptors by antibodies has been reported exclusively in women. This case report is the first description of a male patient with the syndrome of insulin resistance and acanthosis nigricans and focuses attention on features that might mislead one to suspect other causes of insulin resistance.- - - - - - - - - - ranking = 1.4keywords = receptor (Clic here for more details about this article) |
5/52. Subtle radiographic findings of achondroplasia in patients with Crouzon syndrome with acanthosis nigricans due to an Ala391Glu substitution in FGFR3.A unique type of craniofacial dysostosis, Crouzon syndrome with acanthosis nigricans (CAN), has been attributed to a specific substitution (Ala391Glu) in the fibroblast growth factor receptor 3 (FGFR3) gene. At birth, individuals with this disorder have craniosynostosis, ocular proptosis, midface hypoplasia, choanal atresia, hydrocephalus, and they experience the onset of acanthosis nigricans during childhood. We report three cases and compare the clinical characteristics of our cases with the previously reported cases of this disorder. Since the Ala391Glu substitution in FGFR3 is close to the substitutions in the transmembrane domain that result in achondroplasia, we carefully reviewed the skeletal findings in six patients. We identified subtle radiographic findings of achondroplasia in all six cases including narrow sacrosciatic notches, short vertebral bodies, lack of the normal increase in interpediculate distance from the upper lumbar vertebrae caudally, and broad, short metacarpals and phalanges. Even before acanthosis nigricans appears, the presence of choanal atresia and hydrocephalus in an individual with features of Crouzon syndrome should suggest the diagnosis of CAN, and subtle skeletal findings can lend further support to this diagnosis.- - - - - - - - - - ranking = 0.2keywords = receptor (Clic here for more details about this article) |
6/52. Clinical and biochemical findings of a patient with thanatophoric dysplasia type I: additional finding of dicarboxylic aciduria.OBJECTIVE: A long-surviving thanatophoric dysplasia type I patient to age of 6 years is presented. RESULTS AND CONCLUSIONS: Molecular studies revealed a heterozygous point mutation, S249C in the fibroblast growth factor receptor 3 gene. Most of the clinical course was similar to previous reports, including hearing loss and acanthosis nigricans. Abnormal urinary excretion of dicarboxylic acids and 3-hydroxydicarboxylic acids was observed. We hypothesize that this was a consequence of the FGFR3 mutation.- - - - - - - - - - ranking = 0.2keywords = receptor (Clic here for more details about this article) |
7/52. An arginine to cysteine(252) mutation in insulin receptors from a patient with severe insulin resistance inhibits receptor internalisation but preserves signalling events.AIMS/HYPOTHESIS: We examined the properties of a mutant insulin receptor (IR) with an Arg(252) to Cys (IR(R252C)) substitution in the alpha-subunit originally identified in a patient with extreme insulin resistance and acanthosis nigricans. methods: We studied IR cell biology and signalling pathways in Chinese Hamster ovary cells overexpressing this IR(R252C). RESULTS: Our investigation showed an impairment in insulin binding to IR(R252C) related mostly to a reduced affinity of the receptor for insulin and to a reduced rate of IR(R252C) maturation; an inhibition of IR(R252C)-mediated endocytosis resulting in a decreased insulin degradation and insulin-induced receptor down-regulation; a maintenance of IR(R252C) on microvilli even in the presence of insulin; a similar autophosphorylation of mutant IR(R252C) followed by IRS 1/IRS 2 phosphorylation, p85 association with IRS 1 and IRS 2 and Akt phosphorylation similar to those observed in cells expressing wild type IR (IRwt); and finally, a reduced insulin-induced Shc phosphorylation accompanied by decreased ERK1/2 phosphorylation and activity and of thymidine incorporation into dna in cells expressing IR(R252C) as compared to cells expressing IRwt. CONCLUSION/INTERPRETATION: These observations suggest that: parameters other than tyrosine kinase activation participate in or control the first steps of IR internalisation or both; IR-mediated IRS 1/2 phosphorylation can be achieved from the cell surface and microvilli in particular; Shc phosphorylation and its subsequent signalling pathway might require IR internalisation; defective IR endocytosis correlates with an enhancement of some biological responses to insulin and attenuation of others.- - - - - - - - - - ranking = 2.2keywords = receptor (Clic here for more details about this article) |
8/52. A case of Beare-Stevenson cutis gyrata syndrome confirmed by mutation analysis of the fibroblast growth factor receptor 2 gene.This paper reports a case of Beare-Stevenson cutis gyrata syndrome confirmed by dna analysis of the patient's fibroblast growth factor receptor (FGFR) genes. At birth, the patient had ocular proptosis, a red nevus with skin tags on her forehead and an umbilical stump. She developed craniosynostosis, craniofacial dysmorphism and hydrocephalus. Her treatment included forehead and facial advancement and a ventriculoperitoneal shunt. Analysis of the FGFR genes revealed that she was heterozygous for a missense mutation in exon 10 for the FGFR2 protein, resulting in an amino acid substitution of cysteine for tyrosine at residue 375 (Tyr375Cys). This is the fourth case of Beare-Stevenson cutis gyrata syndrome confirmed by mutation analysis of the FGFR genes.- - - - - - - - - - ranking = 1keywords = receptor (Clic here for more details about this article) |
9/52. Autosomal dominant insulin resistance syndrome due to postbinding defect.We investigated a family in which at least 4 men in 3 generations had a syndrome of obesity, mild mental retardation, delayed puberty, macroorchidism, acanthosis nigricans, hyperinsulinemia, and later overt insulin-resistant diabetes mellitus (non-insulin-dependent diabetes mellitus, NIDDM). The patients have markedly curly scalp hair, deficient face and body hair. Their teeth were healthy and normal in size and position. The clinical and biochemical findings and characteristics of the insulin receptors investigated in fibroblasts are reported. There was normal insulin binding to fibroblasts in the 2 brothers and their father. However, insulin-stimulated rna synthesis was decreased as compared to that of normal control individuals. These findings suggest a postbinding defect of insulin action. The pedigree documents an autosomal dominant mode of inheritance. The diagnosis is of practical importance since it enables medical supervision of gene carriers in a preclinical state of atherosclerotic complications and overt diabetes. The findings in this family have relevance also to the explanation of familial mild mental retardation and to the study of different forms of insulin resistance due to a disturbance in biosignal transfer.- - - - - - - - - - ranking = 0.2keywords = receptor (Clic here for more details about this article) |
10/52. Somatic and germline mosaicism for a R248C missense mutation in FGFR3, resulting in a skeletal dysplasia distinct from thanatophoric dysplasia.In this communication, we report the identification of a mosaic R248C missense mutation in the IgII-III linker region of the gene encoding the fibroblast growth factor receptor-3 (FGFR3), in an individual who manifests a skeletal dysplasia and epidermal hyperplasia. By means of Denaturing High Performance Liquid chromatography (DHPLC), we determined that 25% of her lymphocytes are heterozygous for this particular missense mutation in FGFR3, and that 12.5% of her lymphocyte-derived genomic dna encodes a cysteine residue at this position. The proposita has disproportionate short stature, radial head dislocation, coxa vara, and bowing of some of the long bones, associated with an S-shaped deformity of the humerus, accompanied by widespread acanthosis nigricans in the integument. These features do not match any previously described skeletal dysplasia. Further, the proposita's only pregnancy ended in the delivery of a fetus manifesting a lethal short-limbed dwarfism with pulmonary hypoplasia, strongly suggestive of an undiagnosed thanatophoric dysplasia. These findings confirm the proposita to be a somatic and germline mosaic for this particular missense mutation in FGFR3. Thus far, all reported FGFR3 R248C mutations have resulted in thanatophoric dysplasia type I (TDI).- - - - - - - - - - ranking = 0.2keywords = receptor (Clic here for more details about this article) |
| | Next -> |