Johanson-Blizzard syndrome: a prenatal ultrasonographic diagnosis.

Johanson-Blizzard syndrome is a rare autosomal recessive disorder characterized by aplasia of alae nasi, pancreatic insufficiency, aplasia cutis, anorectal anomalies and postnatal growth restriction. In this case report, we describe the prenatal sonographic findings of Johanson-Blizzard syndrome in a 21-week pregnancy of a consanguineous couple. Sonographic findings of aplastic alae nasi (beak-like nose) and dilated sigmoid colon led to the prenatal diagnosis. This is the first report of the prenatal sonographic diagnosis of Johanson-Blizzard syndrome.     

Meckel-Gruber syndrome. Importance of prenatal diagnosis

Prenatal sonographic findings are reported in six fetuses with the Meckel-Gruber syndrome to illustrate the variety of sonographic findings associated with this disorder and to emphasize the importance of prenatal sonography in helping to establish the correct diagnosis. All six fetuses demonstrated evidence of renal cystic dysplasia. In five cases the kidneys were large and echogenic, demonstrating small discrete cysts in the range of 2 to 5 mm. The remaining fetus demonstrated unilateral renal cystic dysplasia and contralateral renal agenesis. Oligohydramnios was noted in all cases and was evident as early as 14 weeks. An occipital cephalocele was demonstrated on sonography in each case although the size and contents of the cephalocele varied significantly. Two fetuses, both in the same family, also demonstrated a cystic mass in the posterior fossa and partial absence of the cerebellum consistent with a Dandy-Walker variant or cerebellar hypoplasia. The concurrence of marked oligohydramnios and bilateral severe renal anomalies should initiate a search for anomalies of the central nervous system indicative of the Meckel-Gruber syndrome. Recurrence of Meckel-Gruber syndrome may be evaluated as soon as 14 weeks, but it may not be reliably excluded until 20 weeks.     

Proof-of-principle rapid noninvasive prenatal diagnosis of autosomal recessive founder mutations

BACKGROUND. Noninvasive prenatal testing can be used to accurately detect chromosomal aneuploidies in circulating fetal DNA; however, the necessity of parental haplotype construction is a primary drawback to noninvasive prenatal diagnosis (NIPD) of monogenic disease. Family-specific haplotype assembly is essential for accurate diagnosis of minuscule amounts of circulating cell-free fetal DNA; however, current haplotyping techniques are too time-consuming and laborious to be carried out within the limited time constraints of prenatal testing, hampering practical application of NIPD in the clinic. Here, we have addressed this pitfall and devised a universal strategy for rapid NIPD of a prevalent mutation in the Ashkenazi Jewish (AJ) population.METHODS. Pregnant AJ couples, carrying mutation(s) in GBA, which encodes acid β-glucosidase, were recruited at the SZMC Gaucher Clinic. Targeted next-generation sequencing of GBA-flanking SNPs was performed on peripheral blood samples from each couple, relevant mutation carrier family members, and unrelated individuals who are homozygotes for an AJ founder mutation. Allele-specific haplotypes were constructed based on linkage, and a consensus Gaucher disease–associated founder mutation–flanking haplotype was fine mapped. Together, these haplotypes were used for NIPD. All test results were validated by conventional prenatal or postnatal diagnostic methods.RESULTS. Ten parental alleles in eight unrelated fetuses were diagnosed successfully based on the noninvasive method developed in this study. The consensus mutation–flanking haplotype aided diagnosis for 6 of 9 founder mutation alleles.CONCLUSIONS. The founder NIPD method developed and described here is rapid, economical, and readily adaptable for prenatal testing of prevalent autosomal recessive disease-causing mutations in an assortment of worldwide populations.FUNDING. SZMC, Protalix Biotherapeutics Inc., and Centogene AG.     

Autosomal recessive progeroid syndrome due to homozygosity for a TOMM7 variant

Multiple genetic loci have been reported for progeroid syndromes. However, the molecular defects in some extremely rare forms of progeria have yet to be elucidated. Here, we report a 21-year-old man of Chinese ancestry who has an autosomal recessive form of progeria, characterized by severe dwarfism, mandibular hypoplasia, hyperopia, and partial lipodystrophy. Analyses of exome sequencing data from the entire family revealed only 1 rare homozygous missense variant (c.86C>T; p.Pro29Leu) in TOMM7 in the proband, while the parents and 2 unaffected siblings were heterozygous for the variant. TOMM7, a nuclear gene, encodes a translocase in the outer mitochondrial membrane. The TOMM complex makes up the outer membrane pore, which is responsible for importing many preproteins into the mitochondria. A proteomic comparison of mitochondria from control and proband-derived cultured fibroblasts revealed an increase in abundance of several proteins involved in oxidative phosphorylation, as well as a reduction in abundance of proteins involved in phospholipid metabolism. We also observed elevated basal and maximal oxygen consumption rates in the fibroblasts from the proband as compared with control fibroblasts. We concluded that altered mitochondrial protein import due to biallelic loss-of-function TOMM7 can cause severe growth retardation and progeroid features.     

Down syndrome: prenatal risk assessment and diagnosis

Down syndrome (trisomy 21) is the most commonly recognized genetic cause of mental retardation. The risk of trisomy 21 is directly related to maternal age. All forms of prenatal testing for Down syndrome must be voluntary. A nondirective approach should be used when presenting patients with options for prenatal screening and diagnostic testing. Patients who will be 35 years or older on their due date should be offered chorionic villus sampling or second-trimester amniocentesis. Women younger than 35 years should be offered maternal serum screening at 16 to 18 weeks of gestation. The maternal serum markers used to screen for trisomy 21 are alpha-fetoprotein, unconjugated estriol and human chorionic gonadotropin. The use of ultrasound to estimate gestational age improves the sensitivity and specificity of maternal serum screening.     

Early prenatal sonographic diagnosis and follow-up of Jeune syndrome.

Jeune syndrome or asphyxiating thoracic dysplasia is an autosomal recessive osteochondrodysplasia. It is one of the six short-rib (polydactyly) syndromes. The disease has a wide spectrum of manifestations, ranging from a latent to a mild or lethal condition. We describe the prenatal sonographic diagnosis of Jeune syndrome at 14 weeks of gestation in a fetus at risk for this condition, and the development of the syndrome throughout the pregnancy.     

Klippel-Trenaunay-Weber syndrome presenting as massive lymphangiohemangioma of the thigh: prenatal diagnosis.

We report a case of Klippel-Trenaunay-Weber syndrome presenting prenatally as a massive congenital lymphangiohemangioma of the thigh. Routine ultrasonographic examination revealed multiple distorted cystic areas extending from the right flank through the right lower extremity of a 30-week fetus. A diagnosis of cystic lymphangioma of the thigh was suspected prenatally. Neonatal evaluation confirmed the prenatal findings. Neonatal color Doppler imaging revealed blood vessels within the tumor. The differential diagnosis is discussed together with available therapeutic procedures.