Phenotype and genotype in mucolipidoses II and III alpha/beta: a study of 61 probands.

BACKGROUND: Mucolipidoses II and III alpha/beta (ML II and ML III) are lysosomal disorders in which the essential mannose 6-phosphate recognition marker is not synthesised on to lysosomal hydrolases and other glycoproteins. The disorders are caused by mutations in GNPTAB, which encodes two of three subunits of the heterohexameric enzyme, N-acetylglucosamine-1-phosphotransferase. OBJECTIVES: Clinical, biochemical and molecular findings in 61 probands (63 patients) are presented to provide a broad perspective of these mucolipidoses. METHODS: GNPTAB was sequenced in all probands and/or parents. The activity of several lysosomal enzymes was measured in plasma, and GlcNAc-1-phosphotransferase was assayed in leucocytes. Thirty-six patients were studied in detail, allowing extensive clinical data to be abstracted. RESULTS: ML II correlates with near-total absence of phosphotransferase activity resulting from homozygosity or compound heterozygosity for frameshift or nonsense mutations. Craniofacial and orthopaedic manifestations are evident at birth, skeletal findings become more obvious within the first year, and growth is severely impaired. Speech, ambulation and cognitive function are impaired. ML III retains a low level of phosphotransferase activity because of at least one missense or splice site mutation. The phenotype is milder, with minimal delays in milestones, the appearance of facial coarsening by early school age, and slowing of growth after the age of 4 years. CONCLUSIONS: Fifty-one pathogenic changes in GNPTAB are presented, including 42 novel mutations. Ample clinical information improves criteria for delineation of ML II and ML III. Phenotype-genotype correlations suggested in more general terms in earlier reports on smaller groups of patients are specified and extended.

Recessive osteogenesis imperfecta caused by LEPRE1 mutations: clinical documentation and identification of the splice form responsible for prolyl 3-hydroxylation.

BACKGROUND: Recessive forms of osteogenesis imperfecta (OI) may be caused by mutations in LEPRE1, encoding prolyl 3-hydroxylase-1 (P3H1) or in CRTAP, encoding cartilage associated protein. These proteins constitute together with cyclophilin B (CyPB) the prolyl 3-hydroxylation complex that hydroxylates the Pro986 residue in both the type I and type II collagen alpha1-chains. METHODS: We screened LEPRE1, CRTAP and PPIB (encoding CyPB) in a European/Middle Eastern cohort of 20 lethal/severe OI patients without a type I collagen mutation. RESULTS: Four novel homozygous and compound heterozygous mutations were identified in LEPRE1 in four probands. Two probands survived the neonatal period, including one patient who is the eldest reported patient (17 7/12 years) so far with P3H1 deficiency. At birth, clinical and radiologic features were hardly distinguishable from those in patients with autosomal dominant (AD) severe/lethal OI. Follow-up data reveal that the longer lived patients develop a severe osteochondrodysplasia that overlaps with, but has some distinctive features from, AD OI. A new splice site mutation was identified in two of the four probands, affecting only one of three LEPRE1 mRNA splice forms, detected in this study. The affected splice form encodes a 736 amino acid (AA) protein with a "KDEL" endoplasmic reticulum retention signal. While western blotting and immunocytochemical analysis of fibroblast cultures revealed absence of this P3H1 protein, mass spectrometry and SDS-urea-PAGE data showed severe reduction of alpha1(I)Pro986 3-hydroxylation and overmodification of type I (pro)collagen chains in skin fibroblasts of the patients. CONCLUSION: These findings suggest that the 3-hydroxylation function of P3H1 is restricted to the 736AA splice form.

Aminoacylase I deficiency: a novel inborn error of metabolism.

This is the first report of a patient with aminoacylase I deficiency. High amounts of N-acetylated amino acids were detected by gas chromatography-mass spectrometry in the urine, including the derivatives of serine, glutamic acid, alanine, methionine, glycine, and smaller amounts of threonine, leucine, valine, and isoleucine. NMR spectroscopy confirmed these findings and, in addition, showed the presence of N-acetylglutamine and N-acetylasparagine. In EBV transformed lymphoblasts, aminoacylase I activity was deficient. Loss of activity was due to decreased amounts of aminoacylase I protein. The amount of mRNA for the aminoacylase I was decreased. DNA sequencing of the encoding ACY1 gene showed a homozygous c.1057 C>T transition, predicting a p.Arg353Cys substitution. Both parents were heterozygous for the mutation. The mutation was also detected in 5/161 controls. To exclude the possibility of a genetic polymorphism, protein expression studies were performed showing that the mutant protein had lost catalytic activity.

A new type of autosomal recessive spondyloepiphyseal dysplasia tarda.

Repeated occurrence of a hitherto unrecognized form of spondyloepiphyseal dysplasia tarda (SED tarda) has been studied in two independent families. Because parental consanguinity was also present in one family, autosomal recessive inheritance is proposed. The onset was in late childhood. The slowly evolving disorder shared several features of the already known types of SED tarda. The radiographic abnormalities were limited to the spine and proximal femora. The patients' hands were normal. The entity described is set apart not only from the X-linked and autosomal-dominant forms of SED tarda but also from the already delineated autosomal recessive types by significant clinical and radiographic differences. Final genotypic characterization must await the results of genetic linkage studies and of appropriate molecular genetics investigations.

Homozygous Gly555Glu mutation in the nuclear-encoded 70 kDa flavoprotein gene causes instability of the respiratory chain complex II.

A homozygous mutation in the flavoprotein (Fp) gene associated with complex II deficiency was demonstrated in a patient with consanguineous parents. She succumbed at 5(1/2) months of age following a respiratory infection. The c1664G-->A transition detected, predicted the substitution of the small uncharged glycine at position 555 by glutamic acid. Her clinical course was at variance with the Leigh syndrome in three previously reported patients due to Fp gene mutations. In this proband, CRM for flavoprotein as well as iron-containing protein (Ip) was decreased, CRM for the entire complex II (130 kDa) being reduced even more. This observation prompts speculation of a labile interaction between Ip and Fp polypeptides and of a key role of the amino acid at position 555 in the interacting domain.

Dominant inheritance of sialuria, an inborn error of feedback inhibition.

"French type" sialuria, a presumably dominant disorder that, until now, had been documented in only five patients, manifests with mildly coarse facies, slight motor delay, and urinary excretion of large quantities (>1 g/d) of free N-acetylneuraminic acid (NeuAc). The basic defect consists of the very rare occurrence of failed feedback inhibition of a rate-limiting enzyme, in this case uridinediphosphate-N-acetylglucosamine (UDP-GlcNAc) 2-epimerase, by a downstream product, in this case cytidine monophosphate (CMP)-NeuAc. We report a new patient with sialuria who has a heterozygous G-->A substitution in nucleotide 848 of the epimerase gene, which results in an R266Q change. The proband's other allele, as expected, had no mutation. However, the heterozygous R266Q mutation was detected in the patient's mother, who has similarly increased urinary levels of free NeuAc, thereby confirming, for the first time, the dominant mode of inheritance of this inborn error. The biochemical diagnosis of the proband was verified by the greatly increased level of free NeuAc in his cultured fibroblasts, the NeuAc distribution, mainly (59%) in the cytoplasm, and by the complete failure of 100 microM CMP-NeuAc to inhibit UDP-GlcNAc 2-epimerase activity in the mutant cells. These findings call for expansion of the phenotype to include adults and for more-extensive assaying of free NeuAc in the urine of children with mild developmental delay. The prevalence of sialuria is probably grossly underestimated.

Subtelomeric familial translocation t(2;7)(q37;q35) leading to partial trisomy 7q35-->qter: molecular cytogenetic analysis and clinical phenotype in two generations.

Few patients with trisomy of the most distal region of chromosome 7q have been described. We report on a familial translocation t(2;7)(q37;q35) leading to trisomy 7q35-->7qter in a child and her paternal uncle and a minimal deletion of distal 2q as demonstrated by FISH with probes located in the chromosome 2q subtelomeric region. The clinical phenotype included macrocephaly and low-set ears, also found in other reported patients trisomic for the distal part of chromosome 7q. Phenotypic findings probably useful for the clinical diagnosis include normal size at birth, large head with frontal bossing, low-set ears of normal shape, small nose and low nasal bridge, feeding difficulties in infancy, and severe neurodevelopmental delay.

Fungal intracranial aneurysm in a child with familial chronic mucocutaneous candidiasis.

UNLABELLED: We report on a patient who presented at 5 years of age with a hemiparesis due to a middle cerebral artery infarction. An embolism had originated from a mycotic aneurysm located in the internal carotid artery. For several months prior to admission he had been suffering from therapeutically resistant candidiasis of the mouth and nails. Family history revealed chronic mycotic infections of the skin, hair, nails and mouth in the father and paternal grandmother suggestive of chronic mucocutaneous candidiasis with autosomal dominant mode of inheritance. Clipping of the aneurysm, after 3 months of anti-mycotic treatment, followed by sustained treatment with itraconazole and fluconazole, led to a favourable outcome. CONCLUSION: Chronic mucocutaneous candidiasis can be associated with an intracranial aneurysm and complicated by cerebral infarction.

The Meier-Gorlin syndrome, or ear-patella-short stature syndrome, in sibs.

The Meier-Gorlin syndrome, first described by Meier and Rothschild [1959: Helv Paediatr Acta 14:213-216] and further delineated by Gorlin et al. [1975: A Selected Miscellany, p 39-50], is characterized by short stature, slender body build, craniofacial anomalies, microtia, delayed skeletal development, hypogonadism, and absence of the patellae. It has also been called the ear-patella-short stature syndrome [Boles et al., 1994: Clin Dysmorphol 3:207-214]. We report on two brothers with Meier-Gorlin syndrome, the younger of whom was more severely affected. Both patients had severe deafness and congenital labyrinthine anomalies, which have not previously been described as features of this syndrome. The neuromotor and mental development of these patients was adversely affected by late diagnosis, deafness, and their sociocultural environment, but their cognitive ability fell within the range observed in other Meier-Gorlin patients. Neuroradiographic imaging and functional inner ear investigations are recommended in the diagnostic workup of this rather specific, probably autosomal recessive mental retardation syndrome with multiple congenital anomalies.

Bruck syndrome: neonatal presentation and natural course in three patients.

Three unrelated patients with congenital arthrogryposis and brittle bones, the main neonatal signs of Bruck syndrome, are presented. In infancy and early childhood recurrent fractures of ribs and long bones and persistent Wormian bones in the calvarium are reminiscent of osteogenesis imperfecta (OI) even with white sclerae, normal dental quality and normal hearing as important clinical negatives. The diagnosis was made before two years of age in two, and in adolescence in the third patient. The latter's radiologically documented long-term natural course reveals slow progressivity of osteopenia and growth deficiency, worsening tendon contractures and pterygia in addition to increasing spine and pelvis deformation. Mental development remains normal. Bruck syndrome is monogenic and probably due to homozygosity of an as yet unidentified gene. As no alteration in the collagens I and III is detected and molecular screening reveals no mutation in the COL1A1 and COL1A2 genes, the pathogenesis of this severe disorder of connective tissue remains largely unknown.

Prenatal diagnosis of pyruvate carboxylase deficiency by direct measurement of catalytic activity on chorionic villi samples.

Pyruvate carboxylase (PC) deficiency is a rare metabolic disorder in infants and children, most frequently with fatal outcome. Its prenatal diagnosis by radiometric assay in cultured amniocytes has previously been reported. We present and discuss the prenatal diagnosis of PC deficiency by direct measurement of PC activity in chorionic villi, in two subsequent pregnancies in a family who previously lost a child affected by PC deficiency. In the next pregnancy PC was unmeasurably low in chorionic villi whereas in control samples its activity was between 0.8 and 3.3 nmol min-1 mg protein-1. Following elective termination of the pregnancy PC was shown to be totally inactive in post-mortem fetal liver. In the most recent pregnancy of the proband's mother PC was normally active in the chorionic villi. The product of this pregnancy was a normal boy.

MRI findings in a neonate with cerebellar agenesis.

Cerebellar agenesis is a rarely observed malformation that is frequently associated with other defects. We describe a neonate with an isolated cerebellar agenesis. In addition to the absence of recognizable cerebellar tissue, cranial magnetic resonance imaging demonstrated a hypoplastic base of the pons and absence of the normal outline of the inferior olives. Other major cerebral malformations were not found. As a developmental defect, cerebellar agenesis is heterogeneous because it occurs either as an anatomically isolated anomaly or as part of a more complex cerebral malformation. The pathogenesis and molecular basis of isolated cerebellar agenesis is unknown.

Diverse mutations in the gene for cartilage oligomeric matrix protein in the pseudoachondroplasia-multiple epiphyseal dysplasia disease spectrum.

Pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (MED) are autosomal dominant osteochondrodysplasias that result in mild to severe short-limb dwarfism and early-onset osteoarthrosis. PSACH and some forms of MED result from mutations in the gene for cartilage oligomeric matrix protein (COMP; OMIM 600310 [http://www3.ncbi.nlm. nih.gov:80/htbin-post/Omim/dispmim?600310]). We report the identification of COMP mutations in an additional 14 families with PSACH or MED phenotypes. Mutations predicted to result in single-amino acid deletions or substitutions, all in the region of the COMP gene encoding the calmodulin-like repeat elements, were identified in patients with moderate to severe PSACH. We also identified within this domain a missense mutation that produced MED Fairbank. In two families, one with mild PSACH and the second with a form of MED, we identified different substitutions for a residue in the carboxyl-terminal globular region of COMP. Both the clinical presentations of these two families and the identification of COMP-gene mutations provide evidence of phenotypic overlap between PSACH and MED. These data also reveal a role for the carboxyl-terminal domain in the structure and/or function of COMP.

Mutational analysis of the SOX9 gene in campomelic dysplasia and autosomal sex reversal: lack of genotype/phenotype correlations.

It has previously been shown that, in the heterozygous state, mutations in the SOX9 gene cause campomelic dysplasia (CD) and the often associated autosomal XY sex reversal. In 12 CD patients, 10 novel mutations and one recurrent mutation were characterized in one SOX9 allele each, and in one case, no mutation was found. Four missense mutations are all located within the high mobility group (HMG) domain. They either reduce or abolish the DNA-binding ability of the mutant SOX9 proteins. Among the five nonsense and three frameshift mutations identified, two leave the C-terminal transactivation (TA) domain encompassing residues 402-509 of SOX9 partly or almost completely intact. When tested in cell transfection experiments, the recurrent nonsense mutation Y440X, found in two patients who survived for four and more than 9 years, respectively, exhibits some residual transactivation ability. In contrast, a frameshift mutation extending the protein by 70 residues at codon 507, found in a patient who died shortly after birth, showed no transactivation. This is apparently due to instability of the mutant SOX9 protein as demonstrated by Western blotting. Amino acid substitutions and nonsense mutations are found in patients with and without XY sex reversal, indicating that sex reversal in CD is subject to variable penetrance. Finally, none of 18 female patients with XY gonadal dysgenesis (Swyer syndrome) showed an altered SOX9 banding pattern in SSCP assays, providing evidence that SOX9 mutations do not usually result in XY sex reversal without skeletal malformations.

Fibrotic eye muscles, Axenfeld anomaly, flat face, and mild developmental retardation: a new example of the Chitty syndrome.

We have studied a girl with fibrotic extrinsic eye muscles, Axenfeld anomaly, unusual facial appearance, mild hydrocephaly, and neurodevelopmental delay. Her condition is similar to the one described recently in members of a single family by Chitty et al. [1991, Am J Med Genet 40:417-420]. We suggest that she represents a second example of what may be called the Chitty syndrome.

Blomstrand lethal osteochondrodysplasia.

We present the clinical, roentgenographic, and histologic abnormalities in a stillborn infant with Blomstrand osteochondrodysplasia. Parental consanguinity and multiplex occurrence in the patients' sibship confirm the hypothesis of autosomal recessive inheritance of this monogenic lethal entity. The unknown genetic defect interferes severely with skeletal growth through lack of chondrocyte multiplication and apparent uncoupling of the processes of enchondral ossification and skeletal growth.

Pseudoachondroplasia and multiple epiphyseal dysplasia due to mutations in the cartilage oligomeric matrix protein gene.

Pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (MED) are dominantly inherited chondrodysplasias characterized by short stature and early-onset osteoarthrosis. The disease genes in families with PSACH and MED have been localized to an 800 kilobase interval on the short arm of chromosome 19. Recently the gene for cartilage oligomeric matrix protein (COMP) was localized to chromosome 19p13.1. In three patients with these diseases, we identified COMP mutations in a region of the gene that encodes a Ca++ binding motif. Our data demonstrate that PSACH and some forms of MED are allelic and suggest an essential role for Ca++ binding in COMP structure and function.