Thanatophoric dysplasia type I presenting with increased nuchal translucency in the first trimester

Thanatophoric dysplasia type 1 with tectal plate dysplasia and aqueductal stenosis

INTRODUCTION

Skeletal dysplasias are a heterogeneous group of disorders comprising of more than 300 entities, many of which manifest in the prenatal period, emphasizing the importance of accurate prenatal diagnosis. Detection of a lethal skeletal dysplasia via prenatal ultrasound is often straightforward. However, establishing the specific diagnosis and detailed evaluation of intracranial anomalies are often challenging. Fetal magnetic resonance imaging (MRI) is superior to ultrasound in the detection of abnormal sulcation pattern, corpus callosal agenesis, and posterior fossa anomalies. Hence, it has the potential of delineating neuroimaging features that may not be fully elucidated by ultrasound. The objective of this article is to describe an unusual case of thanatophoric dysplasia (TD) with dysplastic tectal plate and resultant aqueductal stenosis diagnosed on fetal MRI. To the best of our knowledge, this has never been reported before in the literature. A comprehensive review of literature pertaining to TD-associated CNS abnormalities will also be included.

CONCLUSIONS

Our reported case adds to the current limited knowledge of this rare entity and emphasizes the crucial role of fetal MRI in expanding the neuroimaging phenotypes of TD.

Filho RL, Rosa RFM, Maia CR, Graziadio C, Paskulin GA. Diagnóstico pré-natal de displasia tanatofórica: papel do ultrassom fetal

OBJETIVO: Relatar o caso de um paciente com displasia tanatofórica, uma forma autossômica dominante e letal de nanismo, diagnosticado ainda no período pré-natal, e revisar a literatura, discutindo os principais diagnósticos diferenciais e ressaltando a importância do ultrassom fetal na identificação de fetos portadores dessa displasia. DESCRIÇÃO DO CASO: O paciente é o segundo filho de pais jovens sem história familiar de doenças genéticas. O ultrassom fetal realizado com 35 semanas de gestação mostrou polidrâmnio, proeminência frontal e desproporção entre crânio e tronco, com hipoplasia torácica e encurtamento dos ossos longos, compatível com o diagnóstico de displasia tanatofórica. Ao nascimento, a criança era pequena e possuía hipotonia, macrocefalia, fontanelas amplas, hipoplasia de face média, olhos protrusos, hemangioma plano no nariz e pálpebras, nariz em sela, micrognatia, pescoço e tórax curtos e encurtamento importante de braços, antebraços, coxas e pernas. A avaliação radiográfica mostrou crânio com grande diâmetro transverso, tórax com costelas curtas e corpos vertebrais reduzidos, importante encurtamento e deformidade dos ossos longos dos membros superiores e inferiores (os fêmures eram curvos) e hipoplasia da bacia. Esses achados confirmaram o diagnóstico pré-natal de displasia tanatofórica. O paciente evoluiu para o óbito poucos dias após o nascimento devido à insuficiência respiratória. COMENTÁRIOS: A ultrassonografia fetal é um método não invasivo capaz de diagnosticar inúmeras displasias ósseas, incluindo a tanatofórica. A importância do diagnóstico intra-útero reside no fato de que auxilia no diagnóstico diferencial, e permite o aconselhamento genético à família.

Increased nuchal translucency in euploid fetuses--what should we be telling the parents?

Nuchal translucency (NT) measurement between 11 and 14 weeks' gestation is an undisputed marker for aneuploidies. When conventional karyotyping is normal, enlarged NT is a strong marker for adverse pregnancy outcome, associated with miscarriage, intrauterine death, congenital heart defects, and numerous other structural defects and genetic syndromes. The risk of adverse outcome is proportional to the degree of NT enlargement. Although the majority of structural anomalies are amenable to ultrasound detection, unspecified genetic syndromes involving developmental delay may only emerge after birth. Concern over these prenatally undetectable conditions is a heavy burden for parents. However, following detection of enlarged NT the majority of babies with normal detailed ultrasound examination and echocardiography will have an uneventful outcome with no increased risk for developmental delay when compared to the general population. Counseling should emphasize this to help parents restore hope in normal pregnancy outcome and infant development.

Thanatophoric dysplasia type I associated with increased nuchal translucency in the first trimester: Early prenatal diagnosis using combined ultrasonography and molecular biology

A case of thanatophoric dysplasia (TD) type I associated with severely increased nuchal translucency at first trimester screening for Down syndrome is reported. A 38-year-old woman, G2P1, with previous uneventful pregnancy, was referred for amniocentesis at 16 weeks due to positive first trimester integrated test. Amniocentesis revealed a 46,XX fetus. At 16 weeks gestation, the ultrasound examination of the fetus revealed a narrow chest, short ribs, and a generalized severe shortening of the long bones. The patient underwent a follow-up scan at 19 weeks which demonstrated ultrasound findings consistent with severe rhizomelic micromelia. A wide prenatal panel of gene mutations related with skeletal dysplasia was performed. Nucleotidic sequence using QF-PCR on exons 7,10, 15, 19 of the fibroblast growth factor receptor 3 (FGFR3) demonstrated a 742 C>T (R248C) mutation, which resulted in an Arg248Cys substitution in heterozygous state, leading to a prenatal diagnosis of thanatophoric dysplasia type I. The early diagnosis of this lethal form of skeletal dysplasia directed the prenatal counseling and allowed appropriate obstetric management. Necropsy, post-mortem x-ray, and histologic analysis of the growth plate might aid the diagnosis of TD type I.

First-trimester ultrasound diagnosis of skeletal dysplasia associated with increased nuchal translucency thickness

A series of five cases of skeletal dysplasia is reported in which the diagnosis was reached at the 11-14-week routine ultrasound examination in our referral center. All five cases had increased nuchal translucency thickness (NT) associated with bone abnormalities. We review the current literature on skeletal dysplasia in the first trimester of pregnancy associated with increased NT.