Many people are familiar with the term heart disease. This term is used to label a broad variety of diseases and disorders of the heart. A fairly common type of heart disease is hypertrophic cardiomyopathy or HCM for short. HCM occurs when a part of the heart becomes thickened, and the cause is usually unknown. For about 4% of HCM patients, there is an underlying cause and it actually isn’t HCM at all. Danon disease is a genetic disorder caused by different variants of the LAMP2 gene. Patients with this disease are often misdiagnosed with HCM because that is actually one of the symptoms, but Danon comes with even more difficulties such as skeletal myopathy which causes muscle weakness because of deterioration of the skeletal muscles, intellectual disabilities, and retinal disease which is a condition in the eyes, specifically the retinas, that can cause vision problems and even blindness.

normal vs HCM heart

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Out of these symptoms, HCM is the most concerning. Unfortunately, this condition can be fatal due to sudden cardiac death, which is when someone’s heart just simply stops working usually from an underlying cause that had not been diagnosed or monitored. The symptoms of Danon disease, including HCM and DCM (dilated cardiomyopathy) in females, don’t develop until later in life. Males usually do not present symptoms until puberty, and females not until adulthood. The only real “cure” for heart defects as destructive as this is a heart transplant.

The younger someone is, the more likely they will be to receive a new heart and the easier their recovery will be. Therefore, early diagnosis is key.

An article published on April 5, 2020 discusses the important role that genetic testing can play in early diagnosis. This article uses a case study of a 16-year-old boy who had been diagnosed fairly early with HCM. He had undergone multiple tests and procedures to determine if he was eligible for certain surgeries and drug therapies that could help the HCM, but there was little success. After about a year, the doctors in this study were able to send the young boy to a genetic counselor where him and his family were offered a genetic test that looks at the LAMP2 gene to determine that the HCM was likely caused by Danon Disease.
They performed further testing that showed muscle weakness and mild intellectual impairment both confirming this diagnosis. This diagnosis played an essential part in coming up with an effective treatment plan including a heart transplant, which he had previously been denied because he did not meet certain requirements. This article suggests that LAMP2 genetic testing should be added to the routine genetic screening for HCM. The LAMP2 gene test was crucial in saving this boy’s life, and it could help so many more people if given as a routine option.

Novelli, V. , Bisignani, A. , Pelargonio, G. , et al. (2020). Clinical utility of genetic testing in the early diagnosis of Danon disease mimicking hypertrophic cardiomyopathy: a case report.