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Bethlem myopathy 1B(BTHLM1B)

MedGen UID:
1859128
Concept ID:
C5935580
Disease or Syndrome
Synonym: BTHLM1B
 
Gene (location): COL6A2 (21q22.3)
 
Monarch Initiative: MONDO:0958233
OMIM®: 620725

Definition

Bethlem myopathy-1 (BTHLM1) is a congenital muscular dystrophy characterized by proximal muscle weakness and a combination of distal and proximal flexion joint contractures. The age at onset is highly variable, ranging from infancy to adulthood, and there is intrafamilial variability. Muscle biopsy may show myopathic and dystrophic features; serum creatine kinase is elevated. The progression is slow and ambulation is usually retained into adulthood (summary by Butterfield et al., 2013; Scacheri et al., 2002). For a discussion of genetic heterogeneity of Bethlem myopathy, see BTHLM1A (158810). [from OMIM]

Clinical features

From HPO
Ankle contracture
MedGen UID:
575402
Concept ID:
C0343148
Acquired Abnormality
Knee contracture
MedGen UID:
332406
Concept ID:
C1837263
Anatomical Abnormality
Lack of full passive range of motion (restrictions in flexion, extension, or other movements) of the knee joint resulting from structural changes of non-bony tissues, such as muscles, tendons, ligaments, joint capsules and/or skin.
Proximal muscle weakness
MedGen UID:
113169
Concept ID:
C0221629
Finding
A lack of strength of the proximal muscles.
Distal muscle weakness
MedGen UID:
140883
Concept ID:
C0427065
Finding
Reduced strength of the musculature of the distal extremities.
Elbow contracture
MedGen UID:
331445
Concept ID:
C1833142
Anatomical Abnormality
A limitation in the passive range of motion of the elbow resulting from loss of elasticity in the periarticular tissues owing to structural changes of non-bony tissues, such as muscles, tendons, ligaments, joint capsules or skin.
Muscle fiber splitting
MedGen UID:
322813
Concept ID:
C1836057
Finding
Fiber splitting or branching is a common finding in human and rat skeletal muscle pathology. Fiber splitting refers to longitudinal halving of the complete fiber, while branching originates from a regenerating end of a necrotic fiber as invaginations of the sarcolemma. In fiber branching, one end of the fiber remains intact as a single entity, while the other end has several branches.
Centrally nucleated skeletal muscle fibers
MedGen UID:
330782
Concept ID:
C1842170
Finding
An abnormality in which the nuclei of sarcomeres take on an abnormally central localization (or in which this feature is found in an increased proportion of muscle cells).
Muscle fiber necrosis
MedGen UID:
376893
Concept ID:
C1850848
Pathologic Function
Abnormal cell death involving muscle fibers usually associated with break in, or absence of, muscle surface fiber membrane and resulting in irreversible damage to muscle fibers.
Spinal rigidity
MedGen UID:
346721
Concept ID:
C1858025
Finding
Reduced ability to move the vertebral column with a resulting limitation of neck and trunk flexion.
Interphalangeal joint contracture of finger
MedGen UID:
867413
Concept ID:
C4021784
Anatomical Abnormality
Chronic loss of joint motion in an interphalangeal joint of a finger due to structural changes in non-bony tissue.
Increased endomysial connective tissue
MedGen UID:
867771
Concept ID:
C4022161
Finding
An increased volume of the endomysium, which is a connective tissue sheath that surrounds each muscule fiber. Together, bundles of muscle fibers form a fasciculus, surrounded by another layer of connective tissue called the perimysium.
Abnormality of skeletal muscle fiber size
MedGen UID:
868650
Concept ID:
C4023051
Anatomical Abnormality
Any abnormality of the size of the skeletal muscle cell.
Elevated circulating creatine kinase concentration
MedGen UID:
69128
Concept ID:
C0241005
Finding
An elevation of the level of the enzyme creatine kinase (also known as creatine phosphokinase (CK; EC 2.7.3.2) in the blood. CK levels can be elevated in a number of clinical disorders such as myocardial infarction, rhabdomyolysis, and muscular dystrophy.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  

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