Monitoring of Therapy for Mucopolysaccharidosis Type I Using Dysmorphometric Facial Phenotypic Signatures.

There is a pattern of progressive facial dysmorphology in mucopolysaccharidosis type I (MPS I). Advances in 3D facial imaging have facilitated the development of tools, including dysmorphometrics, to objectively and precisely detect these facial phenotypes. Therefore, we investigated the application of dysmorphometrics as a noninvasive therapy-monitoring tool, by longitudinally scoring facial dysmorphology in a child with MPS I receiving enzyme replacement therapy (ERT) and bone marrow transplantation (BMT). Both dysmorphometric measures showed a decreasing trend, and the greatest differences were found in the severity of facial discordance (Z-RMSE), displaying scores >3 SD higher than the mean at their peak, in comparison to Z-RSD scores that mostly fell within the normative range (maximum; 1.5 SD from the mean). In addition to the general trend of reduced facial dysmorphology with treatment, initial fluctuations were also evident that may have related to transient subcutaneous facial fluctuations, in the context of conditioning for bone marrow transplant. These findings support the potential of our approach as a sensitive, noninvasive, and rapid means of assessing treatment response or failure in clinical trials, and for established therapies, and would be applicable for other inherited disorders of metabolism.