FGFR3 mutations and the skin: report of a patient with a FGFR3 gene mutation, acanthosis nigricans, hypochondroplasia and hyperinsulinemia and review of the literature

Fibroblast growth factor receptor 3 (FGFR3) gene mutations in the germline are well-known causes of skeletal syndromes. Somatic FGFR3 mutations have been found in malignant neoplasms and more recently in several cutaneous elements. We present a 14-year-old girl with mild hypochondroplasia who developed acanthosis nigricans. The report of a K650Q mutation in the FGFR3 gene in a similar case prompted us to conduct a point mutation analysis. The K650Q mutation was confirmed, but in contrast to the previous case, we additionally report findings of hyperinsulinemia. In the recent literature, an increasing number of different cutaneous elements have been found to harbor mutations of FGFR3, suggesting that FGFR3 plays a role in the pathogenesis of these elements. We review the present literature, describing studies in which FGFR3 mutations have been investigated in skin lesions: primarily seborrheic keratoses and epidermal nevi, but also other benign skin tumors and a single case of a squamous cell carcinoma. In addition, an overview of the FGFR3 point mutations in relation to each cutaneous element is given. Based on the current knowledge, it seems likely that these cutaneous lesions have a common genetic background. Our case shows that FGFR3 mutation analysis should be considered in case of the coexistence of acanthosis nigricans and a skeletal dysplasia. Testing for hyperinsulinemia is essential, also if a gene mutation is confirmed.

Leukocyte cDNA analysis of NSD1 derived from confirmed Sotos syndrome patients

BACKGROUND

Haploinsufficiency of the NSD1 gene leads to Sotos syndrome (Sos), which is characterised by excessive growth, especially during childhood, distinct craniofacial features and variable degree of mental impairment. A wide spectrum of NSD1 mutations have been described in Sos patients, ranging from more than 100 different single nucleotide changes, to partial gene deletions, and to microdeletions of various sizes comprising the entire NSD1 locus.

OBJECTIVE

To investigate the NSD1 cDNA sequence in genetically confirmed Sos patients harbouring truncating and missense mutations.

METHOD

Total RNA was isolated from a 250 mul standard EDTA blood sample from nine genetically verified Sos patients, and subsequent reverse-transcribed into cDNA followed by PCR and direct sequencing of specific NSD1 cDNA sequences.

RESULTS

All nine mutations, including missense, nonsense and whole exon deletions, previously identified in genomic DNA, could confidently be detected in cDNA. Several NSD1 transcript splice variants were detected.

CONCLUSION

Despite the fact that Sos is caused by haploinsufficiency, NSD1 transcripts containing nonsense and frame shift mutations can be detected in leukocyte-derived cDNA. The possibility therefore exists that certain NSD1 mutations are expressed and contribute to the phenotypic variability of Sos. NSD1 cDNA analysis is likely to enhance mutation detection in Sos patients.

Carnitine transporter and holocarboxylase synthetase deficiencies in The Faroe Islands

Carnitine transporter deficiency (CTD) and holocarboxylase synthetase deficiency (HLCSD) are frequent in The Faroe Islands compared to other areas, and treatment is available for both disorders. In order to evaluate the feasibility of neonatal screening in The Faroe Islands we studied detection in the neonatal period by tandem mass spectrometry, carrier frequencies, clinical manifestations, and effect of treatment of CTD and HLCSD. We found 11 patients with CTD from five families and 8 patients with HLCSD from five families. The natural history of both disorders varied extensively among patients, ranging from patients who presumably had died from their disease to asymptomatic individuals. All symptomatic patients responded favourably to supplementation with L: -carnitine (in case of CTD) or biotin (in case of HLCSD), but only if treated early. Estimates of carrier frequency of about 1:20 for both disorders indicate that some enzyme-deficient individuals remain undiagnosed. Prospective and retrospective tandem mass spectrometry (MS/MS) analyses of carnitines from neonatally obtained filter-paper dried blood-spot samples (DBSS) uncovered 8 of 10 individuals with CTD when using both C(0) and C(2) as markers (current algorithm) and 10 of 10 when using only C(0) as marker. MS/MS analysis uncovered 5 of 6 patient with HLCSD. This is the first study to report successful neonatal MS/MS analysis for the diagnosis of HLCSD. We conclude that CTD and HLCSD are relatively frequent in The Faroe Islands and are associated with variable clinical manifestations, and that diagnosis by neonatal screening followed by early therapy will secure a good outcome.

Xanthurenic aciduria due to a mutation in KYNU encoding kynureninase

Massive urinary excretion of xanthurenic acid, 3-hydroxykynurenine and kynurenine, known as xanthurenic aciduria or hydroxykynureninuria, in a young Somali boy suggested kynureninase deficiency. Mutation analysis of KYNU encoding kynureninase of the index case revealed homozygosity for a c.593 A > G substitution leading to a threonine-to-alanine (T198A) shift. A younger brother was found to have a similar excretion pattern and the same genotype. At present, neither of the two boys has symptoms of niacin deficiency. This is the first report linking xanthurenic aciduria to a mutation in the gene encoding kynureninase.

Reinvestigation of trihydroxycholestanoic acidemia reveals a peroxisome biogenesis disorder

OBJECTIVE

To determine the enzymatic defect in a patient with ataxia, dysarthric speech, dry skin, hypotonia, and absent reflexes. The patient was previously diagnosed with a presumed deficiency of trihydroxycholestanoyl-CoA oxidase.

BACKGROUND

Peroxisomes harbor a variety of metabolic functions, including fatty acid beta-oxidation, etherphospholipid biosynthesis, phytanic acid alpha-oxidation, and L-pipecolic acid oxidation. This patient was previously described with an isolated peroxisomal beta-oxidation defect caused by a deficiency of the enzyme trihydroxycholestanoyl-CoA oxidase. This was based on the pattern of accumulating metabolites.

METHODS

Measurement of beta-oxidation enzymes, peroxisomal biochemical analysis in body fluids and cultured skin fibroblasts, and DNA analysis of the PEX12 gene were performed.

RESULTS

An isolated beta-oxidation defect in this patient was excluded by measurement of the various beta-oxidation enzymes. The authors found that the patient had a peroxisome biogenesis disorder caused by mutations in the PEX12 gene, although all peroxisomal functions in cultured skin fibroblasts were normal.

CONCLUSIONS

The absence of clear peroxisomal abnormalities in the patient's fibroblasts, including a normal peroxisomal localization of catalase, implies that even when all peroxisomal functions in fibroblasts are normal, a peroxisome biogenesis disorder cannot be fully excluded, and further studies may be needed. In addition, the authors' findings imply that there is no longer evidence for the existence of trihydroxycholestanoyl-CoA oxidase deficiency as a distinct disease entity.

Causality of myelodysplasia and acute myeloid leukemia and their genetic abnormalities

New insights into causative factors for the development of myelodysplasia (MDS) and acute myeloid leukemia (AML), with associations to specific cytogenetic and genetic abnormalities have been obtained primarily from studies of patients with the therapy-related subsets of the two diseases. Current knowledge now makes it possible to distinguish between at least seven major genetic subgroups of MDS and AML, and has directed research towards more specific causative factors also for de novo MDS and AML.

Prepubertal growth in congenital disorder of glycosylation type Ia (CDG-Ia)

AIMS

To delineate the pattern of growth in prepubertal children with congenital disorder of glycosylation type Ia (CDG-Ia) in order to identify critical period(s) and possible cause(s) of growth failure.

METHODS

Longitudinal measurements of weight, length/height, and head circumference from birth to 10 years of age in 25 CDG-Ia patients with the R141H/F119L PMM2 genotype were analysed. The data and derived body mass indices (BMI) were compared with standards and expressed as standard deviation scores (SDS). A linear mixed effects model was fitted to each set of data, and mean curves were estimated.

RESULTS

The mean weight SDS decreased from -0.3 at birth to -3.0 at 7 months of age and remained low or increased slightly. The mean length SDS decreased from zero at birth to -2.4 at 7 months of age followed by a slight increase to a maximum of -1.8 SDS at the end of the second year of life. After age 2 the mean length/height SDS decreased again. The mean BMI SDS at birth was -0.7 and declined to a minimum of -2.8 at the end of the second year of life followed by a gradual increase. The mean head circumference SDS declined gradually from 0 at 3 months of age to -1.9 at age 5.

CONCLUSION

CDG-Ia patients with the R141H/F119L genotype have normal fetal growth and an immediate postnatal onset of severe growth failure. A notable decline in weight end length SDS takes place during the first seven months of life with no prepubertal catch up.

Congenital disorder of glycosylation type Ia (CDG-Ia): phenotypic spectrum of the R141H/F119L genotype

AIMS

To delineate common and variable features and outcome of children with congenital disorder of glycosylation type Ia (CDG-Ia) caused by the frequent R141H/F119L PMM2 genotype.

METHODS

Clinical data on 25 patients (mean age 7.6 years, range 0-19) were analysed.

RESULTS

All patients had an early presentation with severe feeding problems and failure to thrive, hypotonia, hepatic dysfunction, inverted nipples, and abnormal subcutaneous fat pads. Eighteen patients were hospitalised in the neonatal period. Developmental delay was obvious before age 6 months. During the first seven months mean standard deviation score (SDS) for weight and length decreased 2.7 (SD = 2) and 2.4 (SD = 2), respectively. Mental retardation, ataxia, muscular atrophy, and febrile seizures were consistent features after infancy. Variable features included pericardial effusions, afebrile seizures, and stroke like episodes. Computed tomography/magnetic resonance imaging of the brain was normal in two patients examined before 4 months of age, but 18 children examined after 3 months of age had cerebellar atrophy, and 10 children also had supratentorial atrophy. Subsequent imaging showed progression of the cerebellar and supratentorial atrophy in eight and four of 10 children, respectively. Mean head circumference SDS declined from zero to -1.9 SD from age 3 months to 5 years. Motor ability ranged from none to walking with a rolator, and vocabulary ranged from none to comprehensible speech. The overall mortality ascribed to CDG-Ia was 18%.

CONCLUSION

Patients with the R141H/F119L genotype have an early uniform presentation including severe failure to thrive, but their functional outcome is variable. This genotype may well cause clinical manifestations in the severe end of the spectrum of CDG-Ia.

Neonatal screening for galactosemia by quantitative analysis of hexose monophosphates using tandem mass spectrometry: a retrospective study

BACKGROUND

Classic galactosemia (OMIM 230400) is an inherited disorder in the metabolism of galactose caused by deficiency of the enzyme galactose 1-phosphate uridyl transferase (EC 2.7.7.12). Galactosemia leads to accumulation of galactose and galactose 1-phosphate (gal-1-P) in blood and tissues and, if untreated, produces neonatal death or severe mental retardation, cirrhosis of the liver, and cataracts. Hence, the disorder is included in many neonatal screening programs.

METHODS

We retrospectively analyzed filter-paper blood samples obtained 4-8 days postpartum for routine neonatal screening from 12 galactosemia patients and 2055 random controls. Total hexose monophosphates (HMPs) were used as a marker of gal-1-P and were assayed by negative-ion mode electrospray tandem mass spectrometry (tandem MS) with settings biased toward gal-1-P detection. The predominant precursor/product ion pair m/z 259/79 was used to quantify total HMPs by external standardization.

RESULTS

Linear calibration curves were obtained in the range 0-8 mmol/L gal-1-P. The detection limit was 0.1 mmol/L HMP, and total CVs ranged from 13% at the detection limit to <8% at >1 mmol/L HMP. The method was in agreement with an alkaline phosphatase-galactose dehydrogenase method. All samples from galactosemia patients contained increased HMP concentrations (range for patients, 2.6-5.2 mmol/L; range for reference group, <0.10-0.94 mmol/L). The diagnostic sensitivity and specificity were 100% at a cutoff of 1.2 mmol/L HMP. A Duarte/classic galactosemia compound heterozygous sample could be discriminated clearly from both patient and reference samples.

CONCLUSION

Quantitative analysis of HMPs by tandem MS can be used in laboratory investigations of galactosemia.

Design of a pilot study to evaluate tandem mass spectrometry for neonatal screening

In recent years, tandem mass spectrometry has generated great interest as a method for neonatal screening. The basic principle is electronically controlled separation of analytes by their mass-to-charge ratio. The advantage of this detection system is speed, the capability to analyze for many different compounds in a single analysis, and a minimal need for auxilliary assay reagents. The prevailing screening technique uses stable isotope dilution, butylesterification, and MS/MS analysis to quantify amino acids and acylcamitines in neonatal dried blood spot samples. This allows detection of more than 30 inborn errors of metabolism of amino acids, fatty acids, and other organic acids. In Denmark, a large-scale pilot study is being implemented to evaluate the screening potential of tandem mass spectrometry. National patient registers and medical records from clinical genetics units are used to identify cohorts of healthy infants and infants with selected inborn errors of metabolism. The neonatal screening samples of these infants are retrieved from a biobank and are assayed for amino acids and acylcarnitines using tandem mass spectrometry. This study yields decision values for neonatal screening, which will be evaluated in a subsequent 2-year prospective pilot study, offering the test to 140,000 neonates as a voluntary adjunct to the existing screening program. The organization consists of integrated units for neonatal screening and clinical genetics. The effect of the program will be assessed in terms of screening efficiency, cost and short term clinical outcome.

Molecular genetic basis and prevalence of glycogen storage disease type IIIA in the Faroe Islands

Glycogen storage disease type IIIA (GSD IIIA) is caused by mutations of the amyloglucosidase gene (AGL). For most populations, none of the AGL mutations described to date is particularly frequent. In this paper, we report that six children with GSD IIIA from the Faroe Islands were found to be homozygous for the novel nonsense mutation c.1222C>T (R408X) of the AGL gene. This mutation is easily detected by restriction enzyme digest with NsiI after mismatch PCR. Investigating five intragenic polymorphisms, we could show that this mutation was always associated with the same haplotype. The c.1222C>T mutation could be detected on two chromosomes of another 50 unselected GSD IIIA patients of other European or North American origin which means that this mutation plays a minor role worldwide. From the fact that we are currently aware of a total of 14 GSD IIIA cases in the Faroese population of 45 000, the observed prevalence is 1 : 3100. While the novel AGL mutation c.1222C>T was not detectable among 198 German newborns, nine out of 272 children from the Faroese neonatal screening program were found to be heterozygous for this mutation. Thus, the calculated prevalence is 1 : 3600 (95% CI 1:700-1:6400). We conclude that due to a founder effect, the Faroe Islands have the highest prevalence of GSD IIIA world-wide. The detection of the molecular defect has facilitated the diagnosis and has offered the opportunity for prenatal diagnosis in this patient group.

Genetic and metabolic analysis of the first adult with congenital disorder of glycosylation type Ib: long-term outcome and effects of mannose supplementation

We report the diagnosis and follow-up of two sibs reported in 1980 with recurrent venous thromboses and protein-losing enteropathy; one sib with biopsy-proven hepatic fibrosis died at age 5. The combination of symptoms was suggestive of the recently characterized congenital disorder of glycosylation type Ib (CDG-Ib), which is caused by a deficiency of the enzyme phosphomannose isomerase (PMI). An abnormal serum transferrin isoelectric focusing (IEF) pattern and a reduced PMI activity confirmed the diagnosis of CDG-Ib. Furthermore, mutational analysis of the MPI gene revealed two missense mutations, 419 T --> C (I140T) and 636 G --> A (R219Q), a single base substitution in intron 5, 670 + 9G --> A, as well as a polymorphism 1131A --> C (V377V) in both sibs. The surviving 33-year-old sib has had no further symptoms following childhood. Short-term low-dose oral mannose supplementation improved her transferrin IEF pattern and normalized her antithrombin III activity, further substantiating the beneficial effect of mannose in CDG-Ib. When her mannose blood level was measured, she showed a lower steady-state level but a faster mannose clearance rate. These results suggest that the clinical manifestations of PMI deficiency, although serious in childhood, can improve with age, even without mannose therapy, and allow for a normal adult life. However, the long-term prognosis may vary from patient to patient.

[Homocysteine and cardiovascular disease]

Treatment of highly increased plasma concentrations of homocysteine in patients with rare inborn errors of metabolism reduces their risk of vascular thromboses. Many, but not all, epidemiological studies show a relation between slightly increased plasma homocysteine and ischaemic cardiovascular disease. Folic acid supplements reduce plasma homocysteine. The results of ongoing studies of the effect of folic acid and other vitamins on the incidence of cardiovascular disease are expected within the next five years. The available data support the measurement of plasma homocysteine as a part of screening of patients with early and/or frequent vascular thromboses and a disparity between established risk factors and symptoms. Plasma homocysteine > 30 mumol/l in such patients should prompt a search for an inborn error of metabolism.

Classic, atypically severe and neonatal Marfan syndrome: twelve mutations and genotype-phenotype correlations in FBN1 exons 24-40

Mutations in the gene for fibrillin-1 (FBN1) cause Marfan syndrome, an autosomal dominant disorder of connective tissue with prominent manifestations in the skeletal, ocular, and cardiovascular system. There is a remarkable degree of clinical variability both within and between families with Marfan syndrome as well as in individuals with related disorders of connective tissue caused by FBN1 mutations and collectively termed type-1 fibrillinopathies. The so-called neonatal region in FBN1 exons 24-32 comprises one of the few generally accepted genotype-phenotype correlations described to date. In this work, we report 12 FBN1 mutations identified by temperature-gradient gel electrophoresis screening of exons 24-40 in 127 individuals with Marfan syndrome or related disorders. The data reported here, together with other published reports, document a significant clustering of mutations in exons 24-32. Although all reported mutations associated with neonatal Marfan syndrome and the majority of point mutations associated with atypically severe presentations have been found in exons 24-32, mutations associated with classic Marfan syndrome occur in this region as well. It is not possible to predict whether a given mutation in exons 24-32 will be associated with classic, atypically severe, or neonatal Marfan syndrome.

Isolated 2-methylbutyrylglycinuria caused by short/branched-chain acyl-CoA dehydrogenase deficiency: identification of a new enzyme defect, resolution of its molecular basis, and evidence for distinct acyl-CoA dehydrogenases in isoleucine and valine metabolism

Acyl-CoA dehydrogenase (ACAD) defects in isoleucine and valine catabolism have been proposed in clinically diverse patients with an abnormal pattern of metabolites in their urine, but they have not been proved enzymatically or genetically, and it is unknown whether one or two ACADs are involved. We investigated a patient with isolated 2-methylbutyrylglycinuria, suggestive of a defect in isoleucine catabolism. Enzyme assay of the patient's fibroblasts, using 2-methylbutyryl-CoA as substrate, confirmed the defect. Sequence analysis of candidate ACADs revealed heterozygosity for the common short-chain ACAD A625 variant allele and no mutations in ACAD-8 but a 100-bp deletion in short/branched-chain ACAD (SBCAD) cDNA from the patient. Our identification of the SBCAD gene structure (11 exons; >20 kb) enabled analysis of genomic DNA. This showed that the deletion was caused by skipping of exon 10, because of homozygosity for a 1228G-->A mutation in the patient. This mutation was not present in 118 control chromosomes. In vitro transcription/translation experiments and overexpression in COS cells confirmed the disease-causing nature of the mutant SBCAD protein and showed that ACAD-8 is an isobutyryl-CoA dehydrogenase and that both wild-type proteins are imported into mitochondria and form tetramers. In conclusion, we report the first mutation in the SBCAD gene, show that it results in an isolated defect in isoleucine catabolism, and indicate that ACAD-8 is a mitochondrial enzyme that functions in valine catabolism.

Mutation of the gene encoding the ROR2 tyrosine kinase causes autosomal recessive Robinow syndrome

Robinow syndrome is a short-limbed dwarfism characterized by abnormal morphogenesis of the face and external genitalia, and vertebral segmentation. The recessive form of Robinow syndrome (RRS; OMIM 268310), particularly frequent in Turkey, has a high incidence of abnormalities of the vertebral column such as hemivertebrae and rib fusions, which is not seen in the dominant form. Some patients have cardiac malformations or facial clefting. We have mapped a gene for RRS to 9q21-q23 in 11 families. Haplotype sharing was observed between three families from Turkey, which localized the gene to a 4. 9-cM interval. The gene ROR2, which encodes an orphan membrane-bound tyrosine kinase, maps to this region. Heterozygous (presumed gain of function) mutations in ROR2 were previously shown to cause dominant brachydactyly type B (BDB; ref. 7). In contrast, Ror2-/- mice have a short-limbed phenotype that is more reminiscent of the mesomelic shortening observed in RRS. We detected several homozygous ROR2 mutations in our cohort of RRS patients that are located upstream from those previously found in BDB. The ROR2 mutations present in RRS result in premature stop codons and predict nonfunctional proteins.

Osteogenesis imperfecta: mosaicism and refinement of the genotype-phenotype map in OI type III. Mutations in brief no. 242. Online

Non-lethal OI III (OMIM 259420) is caused by structural aberrations of collagen I. We report four novel glycine substitutions, one in the a1 (I) chain of collagen I (G688S) and three in the a2 (I) chain (G241D, G247C, G883V). In each of two families (G241D and G883V), we found parental mosaicism for the substitution explaining recurrence and intrafamilial variability of OI. The G247C and the G883V are the most N-terminally and C-terminally, respectively, placed cysteine and valine substitutions reported. The new substitutions add important information to the genotype-phenotype map and in particular the importance of a-chain stoichiometry is underlined. Data regarding the G688S substitution may suggest a different effect of the two a-chains in the development of dentinogenesis imperfecta (DI).

(G586V) substitutions in the alpha 1 and alpha 2 chains of collagen I: effect of alpha-chain stoichiometry on the phenotype of osteogenesis imperfecta?

Osteogenesis imperfecta (OI) is a congenital disease of connective tissue, most often caused by single amino acid substitutions of glycine residues within the triple helical region of collagen I. Collagen I consists of two alpha 1 chains and one alpha 2 chain. Thus, a substitution in the alpha 1(I) chain is thought to affect the function of the collagen molecule more than would a similar substitution in the alpha 2(I) chain, thereby causing more severe OI. Theoretically this hypothesis may be tested by comparing patients with identical substitutions in different alpha-chains. We present a Gly586Val substitution in the alpha 1(I) chain, and compare our findings to those resulting from Gly586Val substitutions in the alpha 2(I) chain (Forlino et al., 1994; Bateman et al., 1991). Our proband had lethal OI type II. Most alpha-chains of collagen I produced by his cultured fibroblasts were overmodified. The denaturation temperature of the abnormal collagen was 1.5 degrees C below normal. Cyanogen bromide cleavage and subsequent sequencing revealed a G-to-T base substitution at nucleotide 2420 of COL1A1, resulting in a Gly586Val substitution. The collagen findings were almost identical to those reported by Bateman et al. (1991) and Forlino et al. (1994), but the clinical phenotypes were different: the patients with the alpha 2(I) substitutions had OI type IV and III and not the lethal OI type II of our proband. It is known that identical biochemical aberrations in the same chain may have different phenotypic effects, both within families and between non-related patients. This must be taken into account in our cautious proposal that substitutions in the alpha 1(I) chain may have more serious consequences than similar substitutions in the alpha 2(I) chain.

Clustering of mutations associated with mild Marfan-like phenotypes in the 3' region of FBN1 suggests a potential genotype-phenotype correlation

Mutations in the gene for fibrillin-1 (FBN1) cause Marfan syndrome, a dominantly inherited disorder of connective tissue that primarily involves the cardiovascular, ocular, and skeletal systems. There is a remarkable degree of variability both within and between families with Marfan syndrome, and FBN1 mutations have also been found in a range of other related connective tissue disorders collectively termed type-1 fibrillinopathies. FBN1 mutations have been found in almost all of the 65 exons of the FBN1 gene and for the most part have been unique to one affected patient or family. Aside from the "hot spots" for the neonatal Marfan syndrome in exons 24-27 and 31-32, genotype-phenotype correlations have been slow to emerge. Here we present the results of temperature-gradient gel electrophoresis analysis of FBN1 exons 59-65. Six mutations were identified, only one of which had been previously reported. Two of the six mutations were found in patients with mild phenotypes. Taken together with other published reports, our results suggest that a sizable subset (ca. 40%) of mutations in this region is associated with mild phenotypes characterized by the lack of significant aortic pathology, compared with about 7% in the rest of the gene. In two cases, mutations affecting analogous positions within one of the 43 cbEGF modules of FBN1 are associated with mild phenotypes when found in one of the 6 C-terminal modules (encoded by exons 59-63), but are associated with classic or severe phenotypes when found in cbEGF modules elsewhere in the gene.

[Child abuse and osteogenesis imperfecta. How do we distinguish?]

Osteogenesis imperfecta is a hereditary connective tissue disorder. Typical manifestations are fragile bones with multiple bone fractures and bone deformities. A history of minimal or no trauma and recurrent fractures is a feature of OI, but is also typical of non-accidental injury (NAI). OI and NAI are relevant differential diagnoses when a child presents with unexplained fractures. The differential diagnostic problems are reviewed, all of which are important for the child both in terms of treatment and for prognosis, socially and medicolegally. We conclude that comprehensive clinical evaluation is adequate for differential diagnosis and that both OI and NAI can be diagnosed by positive anamnestic and objective signs. Mild OI IV without other signs than fracture(s) is very rare and the new entity temporary brittle bone disease is hypothetical; the diagnosis of these two clinical pictures is unacceptable in small children. Routine analysis of collagens should not be performed.

Abnormal timing in the prenatal ossification of vertebral column and hand in Crouzon syndrome

We report on a radiographically examined fetus (gestational age 13 weeks) with Crouzon syndrome caused by a mutation in the gene encoding the fibroblast growth factor 2 (FGFR2). We found an approximately 2-week delay in vertebral body and hand ossification with normal vertebral arch ossification, suggesting that regionally delayed skeletal maturation might be a manifestation of FGFR2 mutation syndromes. The findings support other studies indicating that different signaling pathways control skeletal maturation in vertebral bodies and vertebral arches.

Carbohydrate-deficient glycoprotein syndrome type 1A: expression and characterisation of wild type and mutant PMM2 in E. coli

We have identified the PMM2 genotypes of 22 unrelated Danish patients with carbohydrate-deficient glycoprotein syndrome type 1A: R141H/F119L (18), R141H/C192G (1), F119L/F119L (1), F119L/G117R (1) and D223E/T237R (1). The lack of patients homozygous for R141H is statistically highly significant, but unexplained. In order to investigate the effect of PMM2 mutations on phosphomannomutase (PMM2) activity, PMM2-cDNA was cloned into a pET3a vector. Following introduction of mutations into PMM2-cDNA by site-specific mutagenesis, wild type and mutant PMM2-cDNA were expressed in E. coli Bl21(DE3) cells, and the activity of PMM2 was determined by an enzymatic assay using mannose 1-phosphate as substrate. Recombinant R141H, G117R, and T237R PMM2 had no detectable catalytic activity, and the F119L PMM2 had 25% of the activity of the wild type. The activity of the C192G and D223E PMM2 was in the normal range, but the affinity for their substrate was lower, and the proteins were more sensitive to increased temperatures. Each patient has at least one mutation which retains residual PMM2 activity. Our results support the hypotheses that a genotype conveying residual PMM2 catalytic activity is required for survival, and that homozygosity for R141H impairs PMM2 to a degree incompatible with life.

Bone mineral content and collagen defects in osteogenesis imperfecta

Whole-body and spine dual-energy X-ray absorptiometry was done in 63 patients with osteogenesis imperfecta aged 5 to 63 y, and the results were compared with OI types and collagen defects. Bone mineral content (BMC)-for-age, bone area (BA)-for-age, bone mineral density (BMD)-for-age, and BMC-for-BA were reduced, especially in patients with OI III/IV and/or in those with a qualitative collagen defect. BA-for-height was normal. Some patients with OI I and/or a quantitative collagen defect had BMD at or above -2 z-scores. We conclude (i) that both BMC and BMD differ significantly between OI types and collagen defects, (ii) that reduced BMC-for-age in OI patients is due mainly to reduced height ("short bones") and reduced BMC-for-BA ("light bones"), whereas BA-for-height ("bone width") is normal, (iii) that most OI patients have lower than average BMC, but in some mildly affected patients brittleness may exist with only small reductions in BMC.

Oral manifestations of Schimmelpenning syndrome: case report and review of literature

Schimmelpenning syndrome (SS) is characterised by specific skin manifestations, skeletal defects, and central nervous system abnormalities. Here, the SS is briefly reviewed, and the oral and dental manifestations are described in a patient whose medical findings were previously published and included severe hypophosphatemic rickets. Significant oral and dental features included papillomatous lesions of the gingiva, hemihyperplasia (hemihypertrophy) of the tongue, bone cysts, aplasia of teeth, enlarged pulp chambers, hypoplastic or absent enamel, and an odontodysplasia-like permanent tooth.

Anthropometry of patients with osteogenesis imperfecta

Standing height, sitting height, armspan, subischial leg length, head circumference, and growth hormone-insulin-like growth factor I (IGF-I) axis were determined in 86 patients with osteogenesis imperfecta. The aim of this study was to determine standing height and body proportions and their variability among osteogenesis imperfecta types and collagen defects. Mean standing height was reduced in all groups of patients, to the greatest extent and variability in osteogenesis imperfecta type III/IV and in those with qualitative collagen defects. The mean standing height of patients with osteogenesis imperfecta was lower than that of their unaffected first degree family members. Truncal height of patients with osteogenesis imperfecta was reduced; head size was increased, and this was more pronounced in patients with osteogenesis imperfecta type III/IV and qualitative collagen defects than in patients with osteogenesis imperfecta type I and quantitative collagen defects. Mean concentrations of IGF-I and IGF binding protein 3 (IGFBP-3) were low, but most values were within age specific reference values. The reduction of standing height appears to correlate with osteogenesis imperfecta type and the type of collagen defect. A relatively short trunk is typical and head circumference and body length are disproportionate.

Recurrent fetal polycystic kidneys associated with glutaric aciduria type II

A woman had two pregnancies terminated in the 20th and 21st weeks of gestation after ultrasonographic detection of enlarged hyperechoic kidneys in both fetuses. The combination of polycystic kidneys and steatotic liver found at autopsy suggested glutaric aciduria type II (GA II), which was confirmed by biochemical investigation. GA II or multiple acyl-CoA dehydrogenase deficiency is an autosomal recessively inherited defect of mitochondrial energy metabolism, which usually results in neonatal death. When pregnancy is terminated because of enlarged hyperechoic kidneys in the fetus, autopsy is crucial for establishing the correct diagnosis. The combination of polycystic kidneys and steatotic liver should bring GA II to mind, and prompt appropriate biochemical investigations so that genetic counselling and first trimester diagnosis can be offered in future pregnancies.

Collagen-derived markers of bone metabolism in osteogenesis imperfecta

Markers of bone formation [C-terminal and N-terminal propeptides of procollagen I (PICP, PINP), osteocalcin and alkaline phosphatase] and bone resorption [C-terminal cross-linked telopeptide of collagen I (ICTP) and hydroxypyridinium cross-links, pyridinoline (Pyr) and deoxypyridinoline (Dpyr)] were measured in 78 osteogenesis imperfecta (OI) patients to investigate bone metabolism in vivo and relate marker concentrations to phenotype and in vitro collagen I defects, as shown by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). PICP and PINP were generally low, and the serum levels were lower in all children and adults with mild OI and a quantitative collagen defect than in patients with severe OI and a qualitative collagen I defect. ICTP, Pyr and Dpyr were generally normal or reduced, but elevated in severely affected adults with a qualitative collagen I defect. The in vivo findings correlated with in vitro results of collagen I SDS-PAGE. Bone turnover is reduced in OI children and mildly affected OI adults, whereas bone resorption is elevated in severely affected adults. These findings may prove helpful for diagnosis and decision-making regarding therapy in OI.

Failure of short-term mannose therapy of patients with carbohydrate-deficient glycoprotein syndrome type 1A

Carbohydrate-deficient glycoprotein syndrome type 1A (CDGS1A) is an inherited disorder with multisystemic abnormalities resulting from failure to generate sufficient lipid-linked oligosaccharide precursor or to transfer the sugar chain to many glycoproteins. Cultured fibroblasts from these patients have reduced incorporation of mannose into glycoproteins which can be corrected by adding D-mannose to the culture medium. Providing dietary mannose to elevate mannose concentrations in vivo therefore might remedy some of the underglycosylation in the patients. Five children with CDGS1A aged 15 months to 14 y completed a protocol of enteral supplementation with D-mannose 100 mg/kg every 3 h for 9 d. The mean S-mannose level increased from 32 microM (range 22-42 microM) to a trough value of 72 microM (range 39-103 microM). No serious side effects were observed. Surprisingly, the mean serum concentration of four glycoproteins (transferrin, alpha1-antitrypsin, antithrombin, and thyroxine-binding globulin) tended to decrease, and the mean serum concentration of carbohydrate-deficient transferrin (CDT) increased. Furthermore, the initially present abnormal isoforms of these glycoproteins and of protein C became more prominent and/or additional abnormal isoforms appeared. This short-term trial does not support a benefit of mannose to the deficient glycosylation of CDGS1A patients.

Absence of homozygosity for predominant mutations in PMM2 in Danish patients with carbohydrate-deficient glycoprotein syndrome type 1

Carbohydrate-deficient glycoprotein syndrome type 1 (CDG1; McKusick No. 212065) is an autosomal recessively inherited disease characterised clinically by central nervous system dysfunction and biochemically by hypoglycosylation of many serum proteins. Most patients with CDG1 have deficient activity of phosphomannomutase. The locus for this enzyme has been mapped to 16p13, and a gene, PMM2, encoding phosphomannomutase has been isolated. We identified 34 mutations on 36 disease chromosomes in 18 unrelated Danish patients with CDG1. All patients have less than 15% residual activity of phosphomannomutase. Two mutations account for 88% of all mutations: F119L and R141H were each found in 16 out of 36 CDG1 alleles. These two mutations were found to be in linkage disequilibrium with two different alleles of the marker D16S3020, suggesting that there is one ancestral origin for each mutation. Two new mutations, G117R and D223E, were identified also. Surprisingly, no patient was homozygous for either of the two common mutations, suggesting that homozygosity for these mutations is either lethal or so benign that such patients are not detected.

Folate and neural tube defects. Recommendations from a Danish working group

A working group was established to evaluate the need for an increased folate intake in Danish women to decrease the risk of neural tube defects (NTDs). NTD are birth defects which include anencephaly, encephalocele and spina bifida. In Denmark the incidence is about 1.4 per 1,000 pregnancies. Folate is a B-vitamin found in most food groups. In case-control studies and randomised studies, a protective effect of folic acid supplements on NTDs has been found. The studies show that a periconceptional folic acid supplement of 360 micrograms to 4 mg daily decreases the recurrence rate of NTDs. Likewise, in the few studies which calculate folate intake from the diet, a lower risk of NTD with higher intake of folate from the diet has been found. The folate intake can be increased by the diet, by folic acid supplements or by fortification of food with folic acid. It is concluded that the incidence of NTDs in Denmark will decrease if the folate intake in fertile women increases. All women planning pregnancy should receive dietary counselling. Women who do not eat according to the Nordic Nutrition Recommendations, and women with an increased risk due to diseases are recommended a supplement of 400 micrograms folic acid daily from a multivitamin/folic acid tablet. Women who have had a child with NTD and women who themselves have NTDs are recommended a supplement of 5 mg folic acid daily. Dietary changes and supplements should be initiated when pregnancy is planned.

Dental manifestations of osteogenesis imperfecta and abnormalities of collagen I metabolism

The in vitro protein-chemical features and the molecular background of osteogenesis imperfecta (OI), a heritable disorder of collagen I metabolism, have been elucidated in recent years. The aim of our study was to find the prevalence of dentinogenesis imperfecta (DI) and other dental anomalies in 88 patients with OI, to compare clinical with radiologic abnormalities, and to correlate these clinical/radiologic findings with the results of gel electrophoresis and molecular studies of collagen I. Twenty-eight percent of OI patients had DI. Most patients with DI had radiologic abnormalities, but some patients had radiologic signs compatible with DI, but no clinical signs of DI. OI type I patients with DI were more severely affected by OI than those without DI. In OI type III and IV, in contrast, there was no difference in overall severity between patients with and without DI. DI was not associated with any particular molecular aberration in any OI type. If defining DI from the presence of both clinical and radiologic signs, collagen I produced by cultured fibroblasts was qualitatively abnormal from all OI patients with DI. Some OI patients had dental abnormalities not resembling DI. A qualitative collagen abnormality could not be found in any of these patients. Denticles, i.e., calcifications within the pulpal cavity, were found more frequently in OI patients than in control subjects.

Anophthalmia-microphthalmia-oblique clefting syndrome: confirmation of the Fryns anophthalmia syndrome

We describe a patient with bilateral extreme microphthalmia with bilateral congenital glaucoma, bilateral medial oblique facial cleft ending in lid colobomas, bilateral stenosis of the choanae, bifid uvula, frontal encephalocele, and premature craniosynostosis. The cause is unknown, but the phenotype resembles the Fryns anophthalmia-plus syndrome, which may be a recessive trait, although intrauterine environmental factors cannot be excluded.

Abnormal metabolism of mannose in families with carbohydrate-deficient glycoprotein syndrome type 1

Patients with carbohydrate-deficient glycoprotein syndrome (CDGS) Type 1 underglycosylate many glycoproteins by failing to add entire N-linked carbohydrate chains to them. The primary defect in these patients has been reported as a > 90% deficiency in phosphomannomutase activity (PMM), the enzyme that converts mannose-6-phosphate to mannose-1-phosphate. This lesion reduces both the amount and the size of the lipid-linked oligosaccharide precursor. We have now analyzed the activity of PMM and the level of glycosylation in cultured fibroblasts as well as the level of blood mannose in seven CDGS Type 1 patients and their parents. All of these patients were approximately 95% deficient in PMM activity and their parents had an average of 51% of control PMM activity. Furthermore, parental fibroblasts showed reduced glycosylation and a higher proportion of truncated N-linked chains compared to those made by control fibroblasts. Addition of 0.25 mM mannose to the culture medium corrected both the underglycosylation and size of the oligosaccharide chains in CDGS Type 1 patients and their parents. Finally, serum from CDGS patients had considerably reduced mannose levels (5-40 microM) compared to normal controls (40-80 microM) and some parents were below normal (16-103 microM). These results suggest that the reduced blood mannose level is a consequence of the PMM deficiency. This is the first inherited disorder in human metabolism that shows a decrease in available mannose. Increasing blood mannose levels might correct some protein underglycosylation in these patients.

Parental mosaicism and autosomal dominant mutations causing structural abnormalities of collagen I are frequent in families with osteogenesis imperfecta type III/IV

Protein-chemical and molecular studies were conducted on all osteogenesis imperfecta (OI) type III/IV patients referred to our hospital during the last 15 y. Of a total of 16 OI type III/IV patients studied, 15 patients were heterozygous for a mutation in one of the two genes coding for collagen I, COL1A1 or COL1A2. Cultured fibroblasts from these 15 patients produced both normal and abnormal collagen I molecules, pointing to a dominant-negative effect of the mutation. Nine mutations had not been described previously. Parental mosaicism was demonstrated in three families. In the 16th child the causative mutation was not found. In conclusion, OI type III/IV in most patients of Western European ancestry is caused by dominant mutations in the genes for collagen I, and recurrence of OI is caused in most cases by parental gonadal mosaicism.

Oral ingestion of mannose elevates blood mannose levels: a first step toward a potential therapy for carbohydrate-deficient glycoprotein syndrome type I

Carbohydrate-deficient glycoprotein syndrome type I (CDGS) is an inherited metabolic disorder with multisystemic abnormalities resulting from a failure to add entire N-linked oligosaccharide chains to many glycoproteins. Fibroblasts from these patients also abnormally glycosylate proteins, but this lesion is corrected by providing 250 microM mannose to the culture medium. This correction of protein glycosylation suggests that providing dietary mannose to elevate blood mannose concentrations might also remedy some of the underglycosylation observed in these patients. We find that ingested mannose is efficiently absorbed and increases blood mannose levels in both normal subjects and CDGS patients. Blood mannose levels increased in a dose-dependent fashion with increasing oral doses of mannose (0.07-0.21 g mannose/kg body weight). Peak blood mannose concentrations occurred at 1-2 h following ingestion and the clearance half-time was approximately 4 h. Doses of 0.1 g mannose/ kg body weight given at 3-h intervals maintained blood mannose concentrations at levels 3- to 5-fold higher than the basal level in both normal controls (approximately 55 microM) and CDGS patients. No side effects were observed for this dosage regimen. These results establish the feasibility of using mannose as a potential therapeutic dietary supplement (nutraceutical) to treat CDGS patients.

Fine mapping of the gene for carbohydrate-deficient glycoprotein syndrome, type I (CDG1): linkage disequilibrium and founder effect in Scandinavian families

Carbohydrate-deficient glycoprotein syndrome type I (CDG I) is characterized clinically by severe nervous system involvement and biochemically by defects in the carbohydrate residues in a number of serum glycoproteins. The CDG1 gene was recently localized by us to a 13-cM interval in chromosome region 16p13. In this study 44 CDG I families from nine countries were analyzed with available markers in a region ranging from marker D16S495 to D16S497, and haplotype and linkage disequilibrium analyses were performed. One specific haplotype was found to be markedly overrepresented in CDG I patients from a geographically distinct region in Scandinavia, strongly indicating that CDG I families in this region share the same ancestral CDG1 mutation. furthermore, analysis of the extent of the common haplotype in these families indicates that the CDG1 gene is located in the region defined by markers D16S513-AFMa284wd5-D16S768-D16S406-D16S502 . The critical CDG1 region, in strong linkage disequilibrium with markers AFMa284wd5, D16S768, and D16S406, thus constitutes less than 1 Mb of DNA and less than 1 cM in the very distal part of the CDG1 region defined by us previously.

Investigation of deletions at 7q11.23 in 44 patients referred for Williams-Beuren syndrome, using FISH and four DNA polymorphisms

Williams syndrome (WS) is associated with a submicroscopic deletion of the elastin gene (ELN) at 7q11.23. The deletion encompasses closely linked DNA markers. We have investigated 44 patients referred for possible WS using fluorescence in situ hybridization (FISH) analysis with a P1 clone containing an insert from the ELN, as well as performing genotype analysis of patients and parents with four DNA polymorphisms. Twenty-four patients were found to have deletions, 19 of whom were found clinically to have typical WS. The facial features were especially characteristic. None of the patients without detectable deletions was reported to have typical WS features, although one had supravalvular aortic stenosis, hypercalcemia, and mental retardation. No evidence was found in this material for variability of the size of the deletion. Our study supports the usefulness of analysis of ELN deletion in WS patients, both for confirmation of diagnosis and for genetic counselling.

Quantification, by solid-phase minisequencing, of the telomeric and centromeric copies of the survival motor neuron gene in families with spinal muscular atrophy

In an analysis of 30 families affected by spinal muscular atrophy (SMA) we have used the solid-phase minisequencing method to determine the ratio between the number of telomeric and centromeric copies of the survival motor neuron gene (SMN and cBCD541 respectively) on normal and SMA chromosomes. This has enabled us to establish haplotypes with regard to SMN and cBCD541, and estimate their frequencies, on both types of chromosomes. Six predominant haplotypes were identified, three for normal chromosomes and three for SMA chromosomes, characterized by having 0, 1, or 2 copies, respectively, of cBCD541. We found evidence for the presence of patients homozygous for a deletion of SMN and with only one copy of cBCD541, but found none deleted for all copies of this gene. Several asymptomatic carriers of SMA with only a single copy of SMN and no copy of cBCD541 were identified. We could not confirm the hypothesis that the presence of more copies of cBCD541 is correlated to a less severe course of the disease. The frequencies of haplotypes characterized by having 0, 1, or 2 copies, respectively, of cBCD541 were found to differ significantly between normal and SMA chromosomes. This distribution can be explained by an underrepresentation of the haplotype completely lacking SMN genes, which is expected to cause early embryonic death in homozygotes. This first report of a direct haplotype analysis of SMN and cBCD541 should help clarify the role of cBCD541 in the pathogenesis of SMA.

Variable clinical expression in a family with OI type IV due to deletion of three base pairs in COL1A1

We have studied a family with autosomal dominant osteogenesis imperfecta (OI) type IV. Electrophoresis of collagen produced by cultured fibroblasts revealed a slower migrating population of collagen I. Cyanogen bromide peptide mapping localised the structural defect to the area of the alpha 1(1)CB3 peptide. Subsequent sequencing revealed a deletion of nucleotides 1964-1966 in exon 27 of COL1A1. By means of restriction enzyme analysis, the deletion could be detected in all affected family members. This in-frame deletion resulted in the removal of alanine-438 and Glu437Asp substitution in the pro alpha 1(I) collagen chain. Clinical variation was considerable among affected family members. The most consistent clinical features were reduced height and extraosseous manifestations of OI.