I Have Questions About Diagnosing Muscular Dystrophy. Have A 16-year-old

I have questions about diagnosing muscular dystrophy. Have a 16-year-old son with global developmental delay, hypotonia, microcephaly and cortical visual impairment . During most recent 4 years, he developed a seizure disorder, then was diagnosed with type 1 diabetes. There are some signs of regression in ambulation stability and increasing malaise/weakness over the past six months. Any suggestions for further evaluation or whether congenital MD might be in the differential?