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Glycogen storage disease IXd(GSD9D)

MedGen UID:
335112
Concept ID:
C1845151
Disease or Syndrome
Synonyms: GLYCOGEN STORAGE DISEASE, TYPE IXd; GSD IXd; GSD9D; Muscle Phosphorylase Kinase Deficiency; PHKA1-Related Phosphorylase Kinase Deficiency
Modes of inheritance:
Autosomal recessive inheritance
MedGen UID:
141025
Concept ID:
C0441748
Intellectual Product
Autosomal recessive inheritance refers to genetic conditions that occur only when mutations are present in both copies of a given gene (i.e., the person is homozygous for a mutation, or carries two different mutations of the same gene, a state referred to as compound heterozygosity).
X-linked recessive inheritance
MedGen UID:
375779
Concept ID:
C1845977
Finding
X-linked recessive inheritance refers to genetic conditions associated with mutations in genes on the X chromosome. A male carrying such a mutation will be affected, because he carries only one X chromosome. A female carrying a mutation in one gene, with a normal gene on the other X chromosome, will be unaffected.
 
Gene (location): PHKA1 (Xq13.1)
OMIM®: 300559
Orphanet: ORPHA715

Definition

Glycogen storage disease type IXd is an X-linked recessive, relatively mild metabolic disorder characterized by variable exercise-induced muscle weakness or stiffness. Most patients have adult-onset of symptoms, and some can remain asymptomatic even in late adulthood. The phenotype is usually only apparent with intense exercise (summary by Preisler et al., 2012). [from OMIM]

Additional description

From GHR
Glycogen storage disease type IX (also known as GSD IX) is a condition caused by the inability to break down a complex sugar called glycogen. The different forms of the condition can affect glycogen breakdown in liver cells or muscle cells or sometimes both. A lack of glycogen breakdown interferes with the normal function of the affected tissue. When GSD IX affects the liver, the signs and symptoms typically begin in early childhood. The initial features are usually an enlarged liver (hepatomegaly) and slow growth. Affected children are often shorter than normal. During prolonged periods without food (fasting), affected individuals may have low blood sugar (hypoglycemia) or elevated levels of ketones in the blood (ketosis). Ketones are molecules produced during the breakdown of fats, which occurs when stored sugars are unavailable. Affected children may have delayed development of motor skills, such as sitting, standing, or walking, and some have mild muscle weakness. Puberty is delayed in some adolescents with GSD IX. In the form of the condition that affects the liver, the signs and symptoms usually improve with age. Typically, individuals catch up developmentally, and adults reach normal height. However, some affected individuals have a buildup of scar tissue (fibrosis) in the liver, which can rarely progress to irreversible liver disease (cirrhosis). GSD IX can affect muscle tissue, although this form of the condition is very rare and not well understood. The features of this form of the condition can appear anytime from childhood to adulthood. Affected individuals may experience fatigue, muscle pain, and cramps, especially during exercise (exercise intolerance). Most affected individuals have muscle weakness that worsens over time. GSD IX can cause myoglobinuria, which occurs when muscle tissue breaks down abnormally and releases a protein called myoglobin that is excreted in the urine. Myoglobinuria can cause the urine to be red or brown. In a very small number of people with GSD IX, the liver and muscles are both affected. These individuals develop a combination of the features described above, although the muscle problems are usually mild.  http://ghr.nlm.nih.gov/condition/glycogen-storage-disease-type-ix

Clinical features

Exercise-induced myoglobinuria
MedGen UID:
348016
Concept ID:
C1860069
Finding
Exercise-induced myoglobinuria
MedGen UID:
348016
Concept ID:
C1860069
Finding
Elevated serum creatine phosphokinase
MedGen UID:
505493
Concept ID:
CN002923
Finding
An elevation of the level of the enzyme creatine kinase (also known as creatine phosphokinase, CPK; EC 2.7.3.2) in the blood. CPK levels can be elevated in a number of clinical disorders such as myocardial infarction, rhabdomyolysis, and muscular dystrophy.
Muscle weakness
MedGen UID:
57735
Concept ID:
C0151786
Finding
A vague complaint of debility, fatigue, or exhaustion attributable to weakness of various muscles. The weakness can be characterized as subacute or chronic, often progressive, and is a manifestation of many muscle and neuromuscular diseases. (From Wyngaarden et al., Cecil Textbook of Medicine, 19th ed, p2251)
Exercise-induced muscle stiffness
MedGen UID:
343388
Concept ID:
C1855579
Finding
Skeletal muscle atrophy
MedGen UID:
505481
Concept ID:
CN002890
Finding
The presence of skeletal muscular atrophy (which is also known as amyotrophy).
Exercise intolerance
MedGen UID:
505555
Concept ID:
CN003200
Finding
Exercise-induced myalgia
MedGen UID:
505583
Concept ID:
CN003377
Finding
The occurrence of an unusually high amount of muscle pain following exercise.

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