Maple syrup urine disease: further evidence that newborn screening may fail to identify variant forms.

Newborn screening (NBS) by tandem mass spectrometry (MS/MS) has allowed for early detection and initiation of treatment in many patients with maple syrup urine disease (MSUD) (OMIM 248600), however, a recent report suggests that variants forms may be missed. Information on these patients is limited. We present clinical, biochemical and molecular information on patients with variant forms of MSUD not detected by the California Newborn Screening Program. Between July 2005 and July 2009, 2200,000 newborns were screened in California by MS/MS. Seventeen cases of MSUD were detected and three (two siblings) were missed. Additionally, the NBS cards of two siblings with late onset MSUD, who were born pre-expanded NBS, were retrospectively analyzed. None of the five patients met criteria to be considered presumptive positive for MSUD (leucine>200micromol/L and a ratio of leucine/alanine>or=1.5). Alloisoleucine (allo-ile) was subsequently analyzed in the NBS cards of all five patients, two of whom were found to have elevated levels. The proband in each family was diagnosed following symptoms triggered by an intercurrent illness or increased protein intake. At diagnosis, leucine levels ranged between 561 and >4528micromol/L, and allo-ile ranged from 137 to 239micromol/L. Two affected siblings had normal plasma amino acids when asymptomatic; however, their biochemical profiles were diagnostic of MSUD during intercurrent illnesses. The median age at diagnosis of all patients was one year (range 0.8-6.7). Heterozygous BCKDHB (E1beta) mutations (c.832G>A/c.970C>T) were identified in one family and a homozygous DBT (E2) sequence variant (c.1430 T>G) in another. The third family had one identifiable DBT mutation (c.827T>G), however, a second mutation was not detected. This report provides further evidence that NBS by MS/MS is unable to detect all cases of MSUD. Second-tier testing with allo-ile may improve sensitivity; however, some children with variant forms will invariably be missed.

Clinical and molecular features of mitochondrial DNA depletion due to mutations in deoxyguanosine kinase.

Published mutations in deoxyguanosine kinase (DGUOK) cause mitochondrial DNA depletion and a clinical phenotype that consists of neonatal liver failure, nystagmus and hypotonia. In this series, we have identified 15 different mutations in the DGUOK gene from 9 kindreds. Among them, 12 have not previously been reported. Nonsense, splice site, or frame-shift mutations that produce truncated proteins predominate over missense mutations. All patients who harbor null mutations had early onset liver failure and significant neurological disease. These patients have all died before 2-years of age. Conversely, two patients carrying missense mutations had isolated liver disease and are alive in their 4th year of life without liver transplant. Five subjects were detected by newborn screening, with elevated tyrosine or phenylalanine. Consequently, this disease should be considered if elevated tyrosine is identified by newborn screening. Mitochondrial DNA content was below 10% of controls in liver in all but one case and modestly reduced in blood cells. With this paper a total of 39 different mutations in DGUOK have been identified. The most frequent mutation, c.763_c.766dupGATT, occurs in 8 unrelated kindreds. 70% of mutations occur in only one kindred, suggesting full sequencing of this gene is required for diagnosis. The presentation of one case with apparent viral hepatitis, without neurological disease, suggests that this disease should be considered in patients with infantile liver failure regardless of the presence of neurological features or apparent infectious etiology.

Prenatal diagnosis of rhizomelic chondrodysplasia punctata due to isolated alkyldihydroacetonephosphate acyltransferase synthase deficiency.

Current practices in prenatal diagnosis of rhizomelic chondrodysplasia punctata (RCDP) are reviewed. A case is presented with a family having one daughter affected with RCDP due to alkyldihydroacetonephosphate acyltransferase synthase (DHAPAT synthase) deficiency, and three subsequent pregnancies. Biochemical test values are presented for the pregnancies and daughter. Post-mortem tests of one fetus of a terminated pregnancy showed that radiologic examination could not make the diagnosis of RCDP. We conclude that biochemical or molecular testing is necessary to accurately diagnose this type of RCDP prenatally.

Genetic heterogeneity of Saethre-Chotzen syndrome, due to TWIST and FGFR mutations.

Thirty-two unrelated patients with features of Saethre-Chotzen syndrome, a common autosomal dominant condition of craniosynostosis and limb anomalies, were screened for mutations in TWIST, FGFR2, and FGFR3. Nine novel and three recurrent TWIST mutations were found in 12 families. Seven families were found to have the FGFR3 P250R mutation, and one individual was found to have an FGFR2 VV269-270 deletion. To date, our detection rate for TWIST or FGFR mutations is 68% in our Saethre-Chotzen syndrome patients, including our five patients elsewhere reported with TWIST mutations. More than 35 different TWIST mutations are now known in the literature. The most common phenotypic features, present in more than a third of our patients with TWIST mutations, are coronal synostosis, brachycephaly, low frontal hairline, facial asymmetry, ptosis, hypertelorism, broad great toes, and clinodactyly. Significant intra- and interfamilial phenotypic variability is present for either TWIST mutations or FGFR mutations. The overlap in clinical features and the presence, in the same genes, of mutations for more than one craniosynostotic condition-such as Saethre-Chotzen, Crouzon, and Pfeiffer syndromes-support the hypothesis that TWIST and FGFRs are components of the same molecular pathway involved in the modulation of craniofacial and limb development in humans.

Genetic mapping of a locus for multiple epiphyseal dysplasia (EDM2) to a region of chromosome 1 containing a type IX collagen gene.

Multiple epiphyseal dysplasia (MED) is a dominantly inherited chondrodysplasia characterized by mild short stature and early-onset osteoarthrosis. Some forms of MED clinically resemble another chondrodysplasia phenotype, the mild form of pseudoachondroplasia (PSACH). On the basis of their clinical similarities as well as similar ultrastructural and biochemical features in cartilage from some patients, it has been proposed that MED and PSACH belong to a single bone-dysplasia family. Recently, both mild and severe PSACH as well as a form of MED have been linked to the same interval on chromosome 19, suggesting that they may be allelic disorders. Linkage studies with the chromosome 19 markers were carried out in a large family with MED and excluded the previously identified interval. Using this family, we have identified an MED locus on the short arm of chromosome 1, in a region containing the gene (COL9A2) that encodes the alpha 2 chain of type IX collagen, a structural component of the cartilage extracellular matrix.

Natural history of mosaic trisomy 14 syndrome.

Trisomy 14 mosaicism produces a distinct phenotype. Among the 13 reported and 2 additional patients, the following findings were present in more than 90%: growth retardation (15/15), psychomotor retardation (10/10), broad nose (13/14), "dysplastic" and/or apparently low-set ears (15/15), micrognathia (15/15), short neck (11/12), congenital heart disease (14/15), and micropenis and cryptorchidism (6/6). Other frequent findings were prominent forehead (12/14), hypertelorism (8/13), narrow palpebral fissure (7/9), large mouth (10/14), cleft or highly arched palate (10/14), body asymmetry (8/12), and abnormal skin pigmentation (6/10). Sex ratio was 6M:9F. Four patients died before age 4 months, while at least 2 patients survived through teens. One boy died at age 3 years following cardiac surgery. One girl with tetralogy of Fallot showed a remarkable improvement in health after Blalock-Taussig procedure. Although the surviving patients showed moderate growth and mental retardation, the oldest surviving woman at 29 years demonstrates functional language and appropriate self help skills.

Radiological findings in Hallermann-Streiff syndrome: report of five cases and a review of the literature.

Hallermann-Streiff syndrome (HSS) is a rare disorder with an associated constellation of radiological findings that may aid in the diagnosis of affected individuals. We reviewed the skeletal surveys of 5 affected individuals and noted some characteristic and constant findings. Radiological findings can include a large, poorly ossified skull with decreased ossification in the sutural areas. There was an increase in the number of Wormian bones. Severe mid-facial hypoplasia was present along with a prominent nasal bone. The skull films also showed an abnormally obtuse or nearly straight gonial angle. The teeth appeared small. The long bones were thin and gracile in appearance and often showed poor demarcation of the cortex from the medullary portion. Abnormal bowing of the radius and ulna was seen neonatally in 2 cases. There was widening at the metaphyseal ends of the long bones. The ribs were thin, but normal in length. The vertebral bodies were noted to be small and 3 cases had platyspondyly. There was a decreased number of sternal ossification enters. The metacarpals were also thin and gracile in appearance with metaphyseal widening. We conclude that these characteristic radiological findings in the newborn with HSS can aid in the diagnosis, and a skeletal survey in suspected individuals may be valuable in confirming the diagnosis.

Ruvalcaba-Myhre-Smith syndrome.

In 1980 a syndrome was first described in two adult males, consisting of macrocephaly, pigmented macules on the glans and shaft of the penis, and hamartomatous intestinal polyps. Since then, 10 additional cases have been identified. Herein, we present two new cases and review the cutaneous manifestations as well as additional features in patients with the Ruvalcaba-Myhre-Smith syndrome.

Trisomy 14 mosaicism syndrome.

A girl with multiple anomalies was found to have trisomy 14 mosaicism. The physical findings in reported cases indicate the condition is a recognizable syndrome.

Epstein-Barr virus infections during pregnancy. A prospective study and review of the literature.

Susceptibility to Epstein-Barr virus (EBV) infection in 1,729 pregnant women was evaluated by screening for EBV antibodies. Fifty-eight subjects (3.4%) had no detectable EBV antibody and were presumably susceptible. Of the 54 women who agreed to participate in this study, none acquired EBV antibody during pregnancy. Our results are in general agreement with some published reports that primary EBV infection during pregnancy is rare. The role of EBV in congenital infections and perinatal morbidity remains to be defined.

Marshall-Smith syndrome: two case reports and a review of pulmonary manifestations.

Two patients with the Marshall-Smith syndrome are described. Both had significant and fatal respiratory distress attributable to this condition. Congenital, functional, and acquired abnormalities of the respiratory tract are described in nine of the 11 case reports in the literature and are characteristic of this syndrome as well as a primary cause of failure to thrive and death in these patients. Unusual immunologic findings in one of our two patients are the first to be reported in the Marshall-Smith syndrome. Quantitation of immune function in other patients with this condition will be helpful in determining the significance of these results. It is hoped that the etiology of the syndrome will be discovered as more cases are recognized and reported by pediatricians caring for infants with failure to thrive, advanced bone age, and chronic respiratory symptomatology.

Affinity of cystathionine beta-synthase for pyridoxal 5'-phosphate in cultured cells. A mechanism for pyridoxine-responsive homocystinuria.

Previous attempts to correlate in vivo pyridoxine-responsiveness with in vitro assays of cystathionine beta-synthase activity in synthase-deficient homocystinuric patients have been only partially successful. All such studies, however, have been conducted with extracts of cultured skin fibroblasts grown in medium containing a high concentration (1,000 ng/ml) of pyridoxal. Having recently shown that such growth conditions may obscure important aspects of enzyme-coenzyme interactions by saturating most synthase molecules with their cofactor, pyridoxal 5'-phosphate, we have established conditions for growth of cells in pyridoxal-free medium. Under these conditions, intracellular pyridoxal 5'-phosphate fell by >95%, and saturation of cystathionine beta-synthase apoenzyme with pyridoxal 5'-phosphate decreased from a predepletion value of 70% to <10%. When such depleted cells were grown in media containing pyridoxal concentrations ranging from 0 to 1,000 ng/ml, cellular pyridoxal 5'-phosphate reached a maximum of 30 ng/mg cell protein at a medium pyridoxal concentration of 100 ng/ml. Maximal saturation of aposynthase with coenzyme in control cells was reached at a medium pyridoxal concentration of 10 ng/ml. In contrast, maximal saturation of residual aposynthase in cells from an in vivo responsive patient was achieved at a medium pyridoxal concentration of 25-50 ng/ml, whereas that from cells from an in vivo unresponsive patient was reached at 100 ng/ml. Estimates of the affinity of control and mutant cystathionine beta-synthase for pyridoxal 5'-phosphate in cell extracts supported the differences observed in intact cells. The apparent K(m) of cystathionine beta-synthase for pyridoxal 5'-phosphate in extracts of depleted cells from four in vivo-responsive patients was two to four times that of control. In contrast, the K(m) for pyridoxal 5'-phosphate in two lines from in vivo nonresponsive patients was 16- and 63-fold normal. These results suggest that cystathionine beta-synthase activity in cells from patients containing a mutant enzyme with a moderately reduced affinity for pyridoxal 5'-phosphate can be increased by pyridoxine supplements in vivo, whereas that from patients whose enzyme has a more dramatically reduced affinity for the coenzyme cannot be so modulated because of limits on the capacity of such cells to accumulate and retain pyridoxal 5'-phosphate.

Ultrasonography and nephrotomography in the presymptomatic diagnosis of dominantly inherited (adult-onset) polycystic kidney disease.

Results of an ongoing four-year study evaluating the role of ultrasonography, nephrotomography, and routine excretory urography in the presymptomatic diagnosis of adult polycystic kidney disease (APKD) are reported. Of 39 asymptomatic individuals who were at risk for APKD, 16 had abnormal studies-eight had bilateral renal cysts withouthepatic cysts on both imaging studies, four had bilateral renal cysts on both imaging studies and hepatic cysts on at least one imaging study, two children who did not have sonographic studies had bilateral renal cysts on nephrotomography, and two children who had a normal nephrotomography had unilateral renal cysts on ultrasonography. Consequently, children of adults with known APKD can be identified as presymptomatic by gray scale ultrasonography, nephrotomography, and/or excretory urography. Gray scale ultrasonography alone is sufficient for family screening for APKD.