Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Singleton Merten syndrome ?
    ### Response:
    Singleton Merten syndrome is an extremely rare, multisystem disorder. The major characteristics are tooth abnormalities (dental dysplasia); calcifications in the aorta and certain valves of the heart (i.e., aortic and mitral valves); and progressive thinning and loss of protein of the bones (osteoporosis), especially the upper and back portions of the skull.
    