Miller-Dieker syndrome. Detection of a cryptic chromosome translocation using in situ hybridization in a family with multiple affected offspring.

Objective: To describe a family in whom fluorescence in situ hybridization allowed for accurate diagnosis of Miller-Dieker syndrome in an at-risk pregnancy and determination of parental carrier status.

Design: Retrospective case analysis and application of a new molecular tool to evaluate the family.

Setting: Health maintenance organization. The family was followed up by the Departments of Medical Genetics, Pediatrics, and Obstetrics and Gynecology, Kaiser Permanente Medical Center, Panorama City, Calif.

Participants: Members of a single family.

Interventions: Clinical evaluation and neuroimaging studies of the proband. Prenatal diagnosis via ultrasonography and amniocentesis. Chromosomal evaluation of the couple and their offspring. In situ hybridization studies in both parents and an affected fetus.

Measurements/main results: We describe a family in whom fluorescence in situ hybridization detected a submicroscopic deletion of the Miller-Dieker syndrome critical region 17p13.3 arising from a cryptic translocation in one of the parents. The proband was determined at birth owing to the presence of multiple congenital anomalies, including low birth weight, microcephaly, agenesis of the corpus callosum, lissencephaly, cerebral atrophy, unilateral ptosis, polydactyly, and omphalocele. High-resolution chromosome-banding analysis findings were normal in the parents and proband, who died at age 4 years. There were four subsequent pregnancies: two ended in first-trimester spontaneous abortion, and in the other two, large omphaloceles were detected in fetuses at 15 and 13 weeks' gestation. Both pregnancies were terminated. Fluorescence in situ hybridization probes for 17p13.3 had become available before the most recent pregnancy and were used to study parental and fetal cells. As a result, a balanced cryptic translocation between chromosome 17 and chromosome 19 was identified in the father: 46,XY,t(17;19)(p13.3q13.33). An unbalanced form of the translocation, involving a deletion of 17p13.3, was detected with fluorescence in situ hybridization in the fetus. This finding was in accordance with a clinical diagnosis of Miller-Dieker syndrome.

Conclusions: Molecular cytogenetic technology should be used in cases of suspected Miller-Dieker syndrome when high-resolution cytogenetic analysis fails to detect del(17) (p13.3). Positive findings should be followed up with parental studies. In addition, omphalocele should be included among the list of malformations that make up the Miller-Dieker syndrome.