A recent republished article appeared in Pediatrics. Dr. Calderon described 6 cases of Congential Myotonic Dystrophy that had global delay. He also complied 55 cases 53 or which had global developmental delay. The diagnosis were by muscle biopsy then no DNA tests were available. The information urged using this as a differential diagnosis.

Below is the PDF of the article

Mental Retardation and Myotonic Dystrophy 1966