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Biomedical subjects

B Steinmann

Publications and source records attributed to B Steinmann.

At least 19 recordsLinked to original sources
PubMed1999

Recombinant families locate the gene for non-type I cystinuria between markers C13 and D19S587 on chromosome 19q13.1.

Cystinuria is an autosomal recessive aminoaciduria in which three urinary phenotypes have been described. The gene responsible for type I, SLC3A1, encodes the amino acid transporter rBAT. This gene is not responsible for types II or III. Recently the type III locus (CSNU3) was mapped by two groups to overlapping 6-Mb regions on chromosome 19q. In the present study, we restrict the critical region for non-type I cystinuria to 2.4 Mb by recombination analysis in Italian, German, and Spanish families. For this purpose, we have used the microsatellite markers described in the region plus new microsatellites that we have developed. Our results locate the non-type I cystinuria gene in an interval flanked by the markers C13 and D19S587, which are about 2.8 cM apart.

Chromosome Mapping↗
PubMed1999

Missense mutations in SGLT1 cause glucose-galactose malabsorption by trafficking defects.

Glucose-galactose malabsorption (GGM) is an autosomal recessive disorder caused by defects in the Na+/glucose cotransporter (SGLT1). Neonates present with severe diarrhea while on any diet containing glucose and/or galactose [1]. This study focuses on a patient of Swiss and Dominican descent. All 15 exons of SGLT1 were screened using single stranded conformational polymorphism analyses, and aberrant PCR products were sequenced. Two missense mutations, Gly318Arg and Ala468Val, were identified. SGLT1 mutants were expressed in Xenopus laevis oocytes for radiotracer uptake, electrophysiological experiments, and Western blotting. Uptakes of [14C]alpha-methyl-d-glucoside by the mutants were 5% or less than that of wild-type. Two-electrode voltage-clamp experiments confirmed the transport defects, as no noticeable sugar-induced current could be elicited from either mutant [2]. Western blots of cell protein showed levels of each SGLT1 mutant protein comparable to that of wild-type, and that both were core-glycosylated. Presteady-state current measurements indicated an absence of SGLT1 in the plasma membrane. We suggest that the compound heterozygote missense mutations G318R and A468V lead to GGM in this patient by defective trafficking of mutant proteins from the endoplasmic reticulum to the plasma membrane.

Cell Membrane↗
PubMed1999

Characterization of eleven novel mutations (M45L, R119H, 544delG, G145V, H154Y, C184Y, D289V, 862+5A, 1172delC, R411X, E459K) in the tissue-nonspecific alkaline phosphatase (TNSALP) gene in patients with severe hypophosphatasia. Mutations in brief no. 217. Online.

Hypophosphatasia is a rare inherited disorder characterized by defective bone mineralization and deficiency of serum and tissue liver/ bone/kidney tissue alkaline phosphatase (L/B/K ALP) activity. We report the characterization of tissue-nonspecific alkaline phosphatase (TNSALP) gene mutations in a series of 9 families affected by severe hypophosphatasia. Fourteen distinct mutations were found, 3 of which were previously reported in the North American or Japanese populations. Seven of the 11 new mutations were missense mutations (M45L, R119H, G145V, C184Y and H154Y, D289V, E459K), the four others were 2 single nucleotide deletions (544delG and 1172delC), a mutation affecting donor splice site (862 + 5A) and a nonsense mutation (R411X).

Alkaline Phosphatase↗
PubMed1999

Type I osteogenesis imperfecta: diagnostic difficulties.

A 65-year-old woman presented with vertebral fractures of the lumbar spine and a history of pathological fractures following minor trauma, which had occurred before the onset of menopause. Her past medical history was significant for intermittent low back pain since childhood, which was attributed to thoracolumbar scoliosis. A diagnosis of unclassifiable osteoporosis was made until invasive diagnostic procedures suggested a mild form of type I osteogenesis imperfecta (OI). In unclear or atypical perimenopausal osteoporosis and diagnosis of OI should be considered.

Absorptiometry, Photon↗
PubMed1999

Ehlers-Danlos syndrome type VII: clinical features and molecular defects.

We evaluated the clinical features, molecular defects, and problems associated with the management of two patients who had type-VII Ehlers-Danlos syndrome and reviewed the cases of eighteen patients with this condition who had been reported on previously. The typical clinical features associated with this syndrome include bilateral congenital dislocation of the hip; severe generalized hypermobility of the joints; multiple dislocations of joints other than the hip; muscular hypotonia; and hyperelasticity, fragility, and a doughy texture of the skin. Collagen and DNA analyses demonstrated that both of our patients had type-VIIB Ehlers-Danlos syndrome, which is caused by heterozygous new mutations of the COL1A2 gene that encodes the proalpha2(I) chain of type-I procollagen. The obligatory GT dinucleotide at the splice donor site of intron 6 was altered in both of our patients: one patient (Case 1) had an A substitution of the G nucleotide, and the other patient (Case 2) had a C substitution of the T nucleotide. Abnormal splicing resulted in the loss of the exon 6-encoded N-telopeptide, which includes the N-proteinase cleavage site. Despite multiple operative procedures, one of our patients, who was thirty-seven years old at the time of the most recent follow-up, continued to have persistent subluxation of the right hip and osteoarthritis of the left hip. Closed reduction of the dislocated hips, regardless of the type of immobilization used, was unsuccessful in all twenty patients. The results of open reduction were improved when capsulorrhaphy was combined with iliac or femoral osteotomy, or both.

Adult↗
PubMed1999

Recessively inherited multiple epiphyseal dysplasia with normal stature, club foot, and double layered patella caused by a DTDST mutation.

We have observed over 25 different mutations in the diastrophic dysplasia sulphate transporter gene (DTDST) in association with the recessive disorders achondrogenesis 1B, atelosteogenesis 2, and diastrophic dysplasia. The c862t (R279W) transition is the most common mutation in non-Finnish patients, but in these disorders it is usually combined with other DTDST mutations. We had not seen a case of homozygosity for c862t (R279W) until we analysed DNA from a 36 year old male with tall-normal stature (180 cm) who asked for genetic counselling for suspected multiple epiphyseal dysplasia. He was treated for club foot and hip dysplasia at birth. Skeletal changes consistent with multiple epiphyseal dysplasia, with the peculiar finding of a double layered patella, were recognised during childhood. Cleft palate, swelling of the ear pinna, and hitch hiker thumb were absent. He was found to be homozygous, and both healthy parents heterozygous, for the R279W mutation in DTDST, and his fibroblasts showed a sulphate incorporation defect typical of DTDST disorders. Counselling was given for a recessive disorder, thereby considerably reducing the probability of affected offspring. Multiple epiphyseal dysplasia is more frequently caused by dominant mutations in the COMP (EDM1, McKusick 132400) and COL9A2 genes (EDM2, McKusick 600204). A few other patients and families with features similar to our proband have been described previously and considered to have autosomal recessive MED (EDM4, McKusick 226900). This observation confirms the existence of this entity and assigns it to the phenotypic spectrum associated with mutations at the DTDST locus.

Adult↗
PubMed1998

Sibs affected with both Ehlers-Danlos syndrome type IV and cystic fibrosis.

We report on the unprecedented combination of two recessively inherited disorders, the kyphoscoliosis type of Ehlers-Danlos syndrome (EDS type VI) and cystic fibrosis (CF), in two sibs born to consanguineous Turkish parents. Because of failure to thrive and bronchitis CF was diagnosed in the index patient early whereas EDS VI was recognized only very late. Both patients had marked muscular hypotonia at birth, delayed gross motor development, progressive kyphoscoliosis, joint dislocations, Marfanoid habitus, hypertrophic and atrophic scars, and osteopenia. EDS VI was proven by collagen studies and the pathognomonic pattern of urinary pyridinolines. Because the genes coding for the two disorders are located on different chromosomes and a chromosomal rearrangement was excluded, we conclude that their combination is a chance association. The cardiopulmonary impairment common to both diseases makes the prognosis dismal.

Amino Acids↗
PubMed1998

Schwartz-Jampel syndrome type 2 and Stüve-Wiedemann syndrome: a case for "lumping".

Recent studies demonstrated the existence of a genetically distinct, usually lethal form of the Schwartz-Jampel syndrome (SJS) of myotonia and skeletal dysplasia, which we called SJS type 2. This disorder is reminiscent of another rare condition, the Stüve-Wiedemann syndrome (SWS), which comprises campomelia at birth with skeletal dysplasia, contractures, and early death. To test for possible nosologic identity between these disorders, we reviewed the literature and obtained a follow-up of the only two surviving patients, one with SJS type 2 at age 10 years and another with SWS at age 7 years. Patients reported as having either neonatal SJS or SWS presented a combination of a severe, prenatal-onset neuromuscular disorder (with congenital joint contractures, respiratory and feeding difficulties, tendency to hyperthermia, and frequent death in infancy) with a distinct campomelic-metaphyseal skeletal dysplasia. The similarity of the clinical and radiographic findings is so extensive that these disorders appear to be a single entity. The follow-up observation of an identical and unique pattern of progressive bone dysplasia in the two patients (one with SJS type 2, one with SWS) surviving beyond infancy adds to the evidence in favor of identity. The hypothesis that SWS and SJS type 2 are the same disorder should be testable by molecular methods.

Abnormalities, Multiple↗
PubMed1998

Ehlers-Danlos syndromes: revised nosology, Villefranche, 1997. Ehlers-Danlos National Foundation (USA) and Ehlers-Danlos Support Group (UK).

Categorization of the Ehlers-Danlos syndromes began in the late 1960s and was formalized in the Berlin nosology. Over time, it became apparent that the diagnostic criteria established and published in 1988 did not discriminate adequately between the different types of Ehlers-Danlos syndromes or between Ehlers-Danlos syndromes and other phenotypically related conditions. In addition, elucidation of the molecular basis of several Ehlers-Danlos syndromes has added a new dimension to the characterization of this group of disorders. We propose a revision of the classification of the Ehlers-Danlos syndromes based primarily on the cause of each type. Major and minor diagnostic criteria have been defined for each type and complemented whenever possible with laboratory findings. This simplified classification will facilitate an accurate diagnosis of the Ehlers-Danlos syndromes and contribute to the delineation of phenotypically related disorders.

Ehlers-Danlos Syndrome↗
PubMed1998

Persistence of the intestinal defect in abetalipoproteinaemia after liver transplantation.

A 16-year-old girl is described with abetalipoproteinaemia who underwent liver transplantation for hepatic cirrhosis. After this procedure her serum lipoprotein profile was corrected; however, fat malabsorption and steatorrhea persisted because the primary defect, a mutant microsomal triglyceride-transfer protein, remains expressed in the intestine.

Abetalipoproteinemia↗
PubMed1998

Fanconi-Bickel syndrome--the original patient and his natural history, historical steps leading to the primary defect, and a review of the literature.

UNLABELLED: Fanconi-Bickel syndrome (FBS) is a rare autosomal recessive disorder of carbohydrate metabolism recently demonstrated to be caused by mutations in Glut2, the gene for the glucose transporter protein 2 expressed in liver, pancreas, intestine and kidney. The disease was first described in a 3-year-old Swiss boy in 1949. Here we report a follow up of this original patient over more than 50 years and show that the typical clinical and laboratory findings of FBS (hepatomegaly secondary to glycogen accumulation, glucose and galactose intolerance, fasting hypoglycaemia, a characteristic proximal tubular nephropathy and severe short stature) persist into adulthood. We further summarize the historical observations that eventually led to the identification of the basic defect of FBS and give an overview of the 82 cases from 70 families in the published literature and from personal communications. CONCLUSION: Although with the first description of a congenital defect of facilitative glucose transport the main steps in the pathophysiology of Fanconi-Bickel syndrome have been elucidated, numerous pathophysiological mechanisms are far from clear and thus encourage the ongoing study of patients with this disorder.

Child, Preschool↗
PubMed1998

Proteoglycan sulfation in cartilage and cell cultures from patients with sulfate transporter chondrodysplasias: relationship to clinical severity and indications on the role of intracellular sulfate production.

Mutations in the diastrophic dysplasia sulfate transporter (DTDST) gene have been associated with a family of chondrodysplasias that includes diastrophic dysplasia (DTD), atelosteogenesis type 2 (AO2) and the lethal condition achondrogenesis type 1B (ACG1B). There is a correlation between the nature of the mutations and the clinical phenotype, but our understanding of the pathophysiology of the disorder, which involves defective sulfation of cartilage proteoglycans, is far from complete. To evaluate the degree of proteoglycan undersulfation in vivo, we have extracted chondroitin sulfate proteoglycans from cartilage of twelve patients with sulfate transporter chondrodysplasias and analyzed their disaccharide composition by HPLC after digestion with chondroitinase ABC. The amount of non-sulfated disaccharide was elevated in patients' samples (controls, 5.5%+/-2.8 (n=10); patients, 11% to 77%), the highest amount being present in ACG1B patients, indicating that undersulfation of chondroitin sulfate proteoglycans occurs in cartilage in vivo and is correlated with the clinical severity. To investigate further the biochemical mechanisms responsible for the translation of genotype to phenotype, we have studied fibroblast cultures of patients with DTD, AO2 and ACG1B, and controls, by double-labelling with [35S]sulfate and [3H]glucosamine. The incorporation of extracellular sulfate, estimated by the 35S/3H ratio in proteoglycans, was reduced in all patients' cells, with ACG1B cells showing the lowest values. However, disaccharide analysis of chondroitin sulfate proteoglycans showed that these were normally sul fated or only moderately undersulfated; marked undersulfation was observed only after addition of the artificial glycosaminoglycan-chain initiator, beta-D-xyloside, to the culture medium. These results suggest that, while utilization of extracellular sulfate is impaired, fibroblasts can replenish their intracellular sulfate pool by oxidizing sulfur-containing compounds (such as cysteine) and thus partially rescue PG sulfation under basal conditions. This rescue pathway becomes insufficient when GAG synthesis rate is stimulated by beta-D-xyloside. These findings may explain why phenotypic consequences of DTDST mutations are restricted to cartilage, a tissue with high GAG synthesis rate and poor vascular supply, and imply that pharmacological therapy aimed at restoring the intracellular sulfate pool might improve PG sulfation in DTD and related disorders.

Anion Transport Proteins↗
PubMed1998

Ehlers-Danlos Syndrome Type VI (EDS VI): problems of diagnosis and management.

Ehlers-Danlos Syndrome Type VI (EDS VI) is a rare autosomal recessively inherited connective tissue disorder, which poses several problems of diagnosis and management. We report on a patient who developed severe kyphoscoliosis long before the diagnosis was reached. We conclude that early biochemical diagnosis and a timely operative procedure by extensive posterior instrumentation is the basis for successful management of this disorder.

Adolescent↗
PubMed1997

In vivo and in vitro characterization of neonatal hyperparathyroidism resulting from a de novo, heterozygous mutation in the Ca2+-sensing receptor gene: normal maternal calcium homeostasis as a cause of secondary hyperparathyroidism in familial benign hypocalciuric hypercalcemia.

We characterized the in vivo, cellular and molecular pathophysiology of a case of neonatal hyperparathyroidism (NHPT) resulting from a de novo, heterozygous missense mutation in the gene for the extracellular Ca2+ (Ca2+(o))-sensing receptor (CaR). The female neonate presented with moderately severe hypercalcemia, markedly undermineralized bones, and multiple metaphyseal fractures. Subtotal parathyroidectomy was performed at 6 wk; hypercalcemia recurred rapidly but the bone disease improved gradually with reversion to an asymptomatic state resembling familial benign hypocalciuric hypercalcemia (FBHH). Dispersed parathyroid cells from the resected tissue showed a set-point (the level of Ca2+(o) half maximally inhibiting PTH secretion) substantially higher than for normal human parathyroid cells (approximately 1.8 vs. approximately 1.0 mM, respectively); a similar increase in set-point was observed in vivo. The proband's CaR gene showed a missense mutation (R185Q) at codon 185, while her normocalcemic parents were homozygous for wild type (WT) CaR sequence. Transient expression of the mutant R185Q CaR in human embryonic kidney (HEK293) cells revealed a substantially attenuated Ca2+(o)-evoked accumulation of total inositol phosphates (IP), while cotransfection of normal and mutant receptors showed an EC50 (the level of Ca2+(o) eliciting a half-maximal increase in IPs) 37% higher than for WT CaR alone (6.3+/-0.4 vs. 4.6+/-0.3 mM Ca2+(o), respectively). Thus this de novo, heterozygous CaR mutation may exert a dominant negative action on the normal CaR, producing NHPT and more severe hypercalcemia than typically seen with FBHH. Moreover, normal maternal calcium homeostasis promoted additional secondary hyperparathyroidism in the fetus, contributing to the severity of the NHPT in this case with FBHH.

Calcium↗