Laboratory abnormalities in ambulatory patients with myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is the most prevalent form of adult muscular dystrophy worldwide. Although well known for the classic manifestations of myotonia, weakness, and early cataracts, it has broad effects on multiple organ systems.

To analyze and compile the laboratory abnormalities of 126 adult patients with DM1.

Laboratory data obtained before treatment were compiled and include values for 45 different laboratory tests and 2860 total studies.

University hospital.

One hundred twenty-six medically healthy, mild to moderately affected, ambulatory patients with DM1 and good venous access enrolled in one of 12 major DM1 clinical trials at a university hospital from 1975 to 2005.

Of the 2860 laboratory studies, results for 470 (16.4%) were outside their reference ranges. Of the 45 types of laboratory tests studied, 41 demonstrated abnormal findings. The relative frequency of an abnormally elevated laboratory value was greater than 50% in several tests, including levels of hemoglobin A(1c), follicle-stimulating hormone, luteinizing hormone in men, and gamma-glutamyltransferase and creatine kinase in women. In addition, levels of lactate dehydrogenase in men and hemoglobin in women were abnormally high or low in more than 50% of the test results evaluated.

There is a high frequency of abnormal laboratory values in DM1 that may form a basis for early screening and monitoring and provide insight into the spectrum of tissues involved in this disease.