Pathogenetic insights from quantification of the cerebriform connective tissue nevus in Proteus syndrome

Background: The plantar cerebriform connective tissue nevus (CCTN) is the most common and problematic cutaneous manifestation of Proteus syndrome. Objective: To gain insights into CCTN pathogenesis and natural history. Methods: The size and location of plantar CCTN was measured on 152 images from 22 individuals with Proteus syndrome by 2 independent, blinded reviewers. Average measures of plantar CCTN were transformed into a linear mixed model to estimate proportionate change in size with age. Results: Median patient age was 6.9 years at study onset. The intraclass correlation coefficient between 2 blinded reviewers was 0.946 for CCTN single measures. The CCTN relative area increased with age in children (n = 18, P <.0001) by 5.6% per year. Confluent papules and nodules extending beyond the boundaries of CCTNs were gradually replaced by typical CCTN over time. The location of CCTN in different individuals overlapped near the ball of the foot. A positive relationship between CCTN growth rate and AKT1 mutant allele frequency was observed (0.62, P =.10, n = 8). Limitations: This was a retrospective review using photographs. Conclusion: CCTN growth is affected by age and extent of the CCTN precursor lesion. Monitoring of CCTN size might prove useful for evaluating drug response in the treatment of Proteus syndrome.