MYOTONIC DYSTROPHY TYPE II (DM2)

Myotonic Dystrophy Type II, also known as Proximal Myotonic Myopathy, is a condition that affects skeletal and smooth muscles. It less commonly affects the eyes, the heart, the endocrine system and the central nervous system.

Clinical features of Myotonic Dystrophy Type II

Typically adult onset in nature, clinical symptoms may include:

• muscle weakness typically affecting neck and finger flexors and hip-girdle muscles
• myotonia including grip myotonia, percussion myotonia and/or leg myotonia
• cataracts
• cardiac issues with conduction or progressive cardiomyopathy
• endocrine issues including insulin insensitivity

Diagnosis of Myotonic Dystrophy Type II

Myotonic Dystrophy Type II is caused by expansion of the CCTG repeat within the first intron of the CNBP gene.

Genomic Unity^® Neuromuscular Disorders Analysis is a genetic test that uses a PCR-free whole genome sequencing (WGS) methodology. The single method platform enables comprehensive analysis of all major variant types within genes associated with neuromuscular disorders. This test specifically includes sequence, del/dup and CCTG repeat expansion analysis of the CNBP gene.

Differential diagnosis of myotonic disorders

With its broad coverage of >120 genes associated with neuromuscular disorders, Genomic Unity^® Neuromuscular Disorders Analysis makes it possible to differentiate Myotonic Dystrophy Type II from among heterogeneous myotonic disorders with overlapping clinical features.

Genomic Unity^® Neuromuscular Disorders Analysis additionally includes:

• sequence, del/dup and CTG repeat expansion analysis of the DMPK gene which causes the oftentimes more severe Myotonic Dystrophy Type I (DM1)
• sequence and del/dup analysis of CLCN1 and other genes that cause myotonia congenita
• sequence and del/dup analysis of SCN4A and other genes that cause Paramyotonia Congenita, Potassium aggravated myotonia,  Potassium-sensitive periodic paralysis and other sodium channel myotonias