Transvaginal sonographic detection of adducted thumbs, hydrocephalus, and agenesis of the corpus callosum at 22 postmenstrual weeks: the masa spectrum or L1 spectrum. A case report and review of the literature.

Prenatal diagnosis of non-chromosomal syndromes relies, among others, on the detection of specific morphological findings. In rare syndromes the index case may not be prenatally diagnosed but subsequent pregnancies may benefit from early diagnosis. In this article we discuss the clinical spectrum of an X-linked hereditary disease which contains hydrocephalus, congenital agenesis of the corpus callosum, adducted thumbs, shuffling gait, aphasia, mental retardation, and at times other associated findings. The purpose of this case report is to describe the prenatal sonographic findings of a fetus affected with adducted thumbs, hydrocephaly, and agenesis of te corpus callosum. The patient was referred at 22 1/2 weeks' gestation for prenatal diagnosis. Ultrasound revealed a male fetus with dilatation of the lateral ventricles and partial agenesis of the corpus callosum. The fetal hands showed the thumbs to be fixed in a flexed-adducted position. These findings were consistent with the MASA spectrum (mental retardation-aphasia-shuffling gait-adducted thumbs) present in the older brother. The patient elected to terminate the pregnancy and autopsy confirmed the sonographic findings. In conclusion, prenatal sonography, especially the presence of adducted thumbs, allowed prenatal diagnosis of the second affected child with the MASA spectrum in this family. This morphology-based approach becomes feasible between postmenstrual weeks 15 and 20. Prior to this gestational age, the diagnosis should rely on molecular biology tests.