Bilambdoid and sagittal synostosis (BLSS), a rare form of multisutural craniosynostosis, is sometimes known as the Mercedes-Benz syndrome due to the appearance of the fused sagittal and bilateral lambdoid sutures. Although previous studies have described some of its clinical features, the pathology of this disease is not yet fully understood. Moreover, it has been pointed out that BLSS is more common among individuals of Hispanic ethnicity, but its incidence in Asia remains unclear. In the present study, BLSS cases in Japan were analyzed to determine the characteristics of the condition in Japan. Three hospitals in Tokyo participated in the present study. Patients with BLSS who underwent cranial remodeling were included. Data on patient demographics, clinical symptoms, status of the cranial sutures, morphological subclassification, surgical procedures, developmental status, and genetic mutations were analyzed. In total, 22 patients met the enrollment criteria and were included, indicating a higher incidence of BLSS in Japan than in other nations reported in previous studies. In terms of morphological subclassification, there were 15 brachycephalic, 4 dolichocephalic, and 3 normocephalic. For the initial cranial procedure, 7 patients underwent a single-stage cranioplasty, 13 underwent a posterior distraction, and 2 underwent lateral expansion. Patients with a normocephalic cranial morphology tended to undergo surgery at an older age than patients with the other two types. Appropriate timing for surgery is important for healthy development; hence, surgeons should remember that BLSS can lead to "balanced dysmorphism" that may have led to a delay in diagnosis due to its normal-looking morphology.
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