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Cystic Hygroma


Introduction

Cystic hygroma (CH) is a congenital lymphatic malformation. It is the most frequently observed fetal neck pathology on prenatal ultrasound (US).

Disease

Definition

CH is an abnormality of the vascular lymphatic system, characterized by the development of distended fluid-filled spaces, typically affecting the fetal neck (80% of cases). Based on the presence of septations, it can be classified into septated or nonseptated CH .

Prevalence and Epidemiology

The true incidence of CH is unknown. It has been reported to be 1 : 6000 at birth and 1 : 750 among spontaneous abortions. Data from the FASTER (First and Second Trimester Evaluation of Risk) trial showed an overall prevalence of CH at about 1 : 100, whereas septated CH affects 1 : 285 fetuses in the first trimester.

Etiology and Pathophysiology

CH is frequently associated with other malformations, particularly congenital heart defects (CHD) and chromosomal abnormalities (75% of cases). Some studies suggest that septations predict an increased likelihood of aneuploidies, but this notion has not been confirmed by others. Turner syndrome is the most common associated chromosomal abnormality, affecting approximately 60% of cases. More recent studies suggest a higher prevalence of Down syndrome. Other chromosomal abnormalities include autosomal trisomies, Klinefelter syndrome, partial trisomies, partial monosomies, translocations, and mosaicisms. Genomic microarray analysis may lead to a decrease in the number of undiagnosed genetics disorders when compared with conventional karyotype. Microarrays enable higher resolution, with 22q11.2 microdeletion being one of the most frequently detected imbalance overlooked by conventional karyotype. CH has been related to inherited disorders and malformation syndromes in euploid fetuses ( Table 70.1 ), maternal infection, and drug intake including alcohol, aminopterin, and trimethadione.

TABLE 70.1
GENETIC AND MALFORMATION SYNDROMES ASSOCIATED WITH CYSTIC HYGROMA

  • Achondrogenesis type II

  • Achondroplasia

  • Beckwith-Wiedemann syndrome

  • Brachmann-de Lange syndrome

  • Campomelic dysplasia

  • Congenital adrenal hyperplasia

  • Cowchock syndrome

  • Cowden disease

  • Cumming syndrome

  • de Lange syndrome

  • Distichiasis-lymphedema syndrome

  • Fanconi pancytopenia syndrome

  • Fraser syndrome

  • Fryns syndrome

  • Hereditary lymphedema

  • Multiple pterygium syndrome

  • Noonan syndrome

  • Oculodentodigital syndrome

  • Opitz-Frias syndrome

  • Pena-Shokeir syndrome

  • Polysplenia syndrome

  • Proteus syndrome

  • Roberts syndrome

  • Thrombocytopenia–absent radius

  • VACTERL association

  • Williams syndrome

  • Zellweger syndrome

VACTERL, V ertebral, a nal, c ardiac, t racheal, e sophageal, r enal, and l imb anomalies.

CH is normally caused by aberrant development of lymphatic vessels, as a consequence of an abnormal or absent connection with the venous system, leading to lymphatic stasis and enlargement of the jugular sacs ( Fig. 70.1 ). Progressive obstruction may lead to thoracic, pericardial, and abdominal effusions. However, if an alternative route of lymphatic flow is established, the distended lymphatic sacs collapse, and the hygroma resolves either completely or showing distended jugular lymph sacs on either side of the fetal neck ( Fig. 70.2 ).

Fig. 70.1, Axial view of septated CH in second trimester. The nuchal ligament is identified.

Fig. 70.2, Dilated jugular sacs (JS) in a case of resolved CH.

Manifestations of Disease

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