2008 ICD-9-CM Volume 1 Diagnosis Codes Home > Diseases Of The Nervous System And Sense Organs 320-389 > Disorders Of The Peripheral Nervous System 350-359 > Muscular Dystrophies And Other Myopathies 359.* > 2008 ICD-9-CM Diagnosis 359.2 Myotonic disorders  On October 1, 2008 the 2009 ICD-9-CM codes came into effect. Therefore, this code may be out of date. The 2009 version of ICD-9-CM 359.2 can be accessed here. A dominantly inherited muscle disease that begins in early childhood and is characterized by severe myotonia (delayed relaxation of a muscle) after forceful voluntary contractions. Muscular hypertrophy is common and myotonia may impair ambulation and other movements. Myotonia typically becomes less severe with repetitive voluntary contractions of the affected muscles. Generalized myotonia (of Becker) is an autosomal recessive variant of myotonia congenita that may feature more severe myotonia and muscle wasting. (From Adams et al., Principles of Neurology, 6th ed, pp1476-7; Joynt, Clinical Neurology, 1997, Ch53, p18) An autosomal dominant neuromuscular disorder which usually presents in early adulthood, characterized by progressive muscular atrophy (most frequently involving the hands, forearms, and face), myotonia, frontal baldness, lenticular opacities, and testicular atrophy. Cardiac conduction abnormalities, diaphragmatic weakness, and mild mental retardation may also occur. Congenital myotonic dystrophy is a severe form of this disorder, characterized by neonatal MUSCLE HYPOTONIA, feeding difficulties, respiratory muscle weakness, and an increased incidence of MENTAL RETARDATION. (From Adams et al., Principles of Neurology, 6th ed, pp1423-5; Joynt, Clinical Neurology, 1997, Ch16, pp16-7) Diseases characterized by MYOTONIA, which may be inherited or acquired. Myotonia may be restricted to certain muscles (e.g., intrinsic hand muscles) or occur as a generalized condition. These disorders may be associated with abnormal muscle SODIUM CHANNEL and CHLORIDE CHANNELS. MYOTONIC DYSTROPHY and MYOTONIA CONGENITA represent two relatively common forms of this disorder. Proximal myotonic myopathy often presents with myotonia and muscle pain in early adulthood and later in life thigh muscle weakness and cataracts develop. (From Adams et al., Principles of Neurology, 6th ed, p1392) 359.2 is a non-specific code that cannot be used to specify a diagnosis View the ICD-9-CM Volume 1 359.* hierarchy ICD9Data's sister site ProcedureCodes.com launches with the 2008/09 CPT® codes - read more on the ICD9Data.com blog. 359.2 excludes: periodic paralysis (359.3)