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Nemaline myopathy 4(CMYP23)

MedGen UID:
324513
Concept ID:
C1836447
Disease or Syndrome
Synonyms: CMYP23; CONGENITAL MYOPATHY 23; Nemaline myopathy caused by mutation in the tropomyosin 2 gene
 
Gene (location): TPM2 (9p13.3)
 
Monarch Initiative: MONDO:0012240
OMIM®: 609285

Definition

Nemaline myopathy is divided into six types. In order of decreasing severity, the types are: severe congenital, Amish, intermediate congenital, typical congenital, childhood-onset, and adult-onset. The types are distinguished by the age when symptoms first appear and the severity of symptoms; however, there is overlap among the various types. The severe congenital type is the most life-threatening. Most individuals with this type do not survive past early childhood due to respiratory failure. The Amish type solely affects the Old Order Amish population of Pennsylvania and is typically fatal in early childhood. The most common type of nemaline myopathy is the typical congenital type, which is characterized by muscle weakness and feeding problems beginning in infancy. Most of these individuals do not have severe breathing problems and can walk unassisted. People with the childhood-onset type usually develop muscle weakness in adolescence. The adult-onset type is the mildest of all the various types. People with this type usually develop muscle weakness between ages 20 and 50.

Nemaline myopathy is a disorder that primarily affects skeletal muscles, which are muscles that the body uses for movement. People with nemaline myopathy have muscle weakness (myopathy) throughout the body, but it is typically most severe in the muscles of the face; neck; trunk; and other muscles close to the center of the body (proximal muscles), such as those of the upper arms and legs. This weakness can worsen over time. Affected individuals may have feeding and swallowing difficulties, foot deformities, abnormal curvature of the spine (scoliosis), and joint deformities (contractures). Most people with nemaline myopathy are able to walk, although some affected children may begin walking later than usual. As the condition progresses, some people may require wheelchair assistance. In severe cases, the muscles used for breathing are affected and life-threatening breathing difficulties can occur. [from MedlinePlus Genetics]

Clinical features

From HPO
Scapular winging
MedGen UID:
66822
Concept ID:
C0240953
Anatomical Abnormality
Abnormal protrusion of the scapula away from the surface of the back.
Limb muscle weakness
MedGen UID:
107956
Concept ID:
C0587246
Finding
Reduced strength and weakness of the muscles of the arms and legs.
Feeding difficulties in infancy
MedGen UID:
436211
Concept ID:
C2674608
Finding
Impaired feeding performance of an infant as manifested by difficulties such as weak and ineffective sucking, brief bursts of sucking, and falling asleep during sucking. There may be difficulties with chewing or maintaining attention.
Waddling gait
MedGen UID:
66667
Concept ID:
C0231712
Finding
Weakness of the hip girdle and upper thigh muscles, for instance in myopathies, leads to an instability of the pelvis on standing and walking. If the muscles extending the hip joint are affected, the posture in that joint becomes flexed and lumbar lordosis increases. The patients usually have difficulties standing up from a sitting position. Due to weakness in the gluteus medius muscle, the hip on the side of the swinging leg drops with each step (referred to as Trendelenburg sign). The gait appears waddling. The patients frequently attempt to counteract the dropping of the hip on the swinging side by bending the trunk towards the side which is in the stance phase (in the German language literature this is referred to as Duchenne sign). Similar gait patterns can be caused by orthopedic conditions when the origin and the insertion site of the gluteus medius muscle are closer to each other than normal, for instance due to a posttraumatic elevation of the trochanter or pseudarthrosis of the femoral neck.
Hyporeflexia
MedGen UID:
195967
Concept ID:
C0700078
Finding
Reduction of neurologic reflexes such as the knee-jerk reaction.
Motor delay
MedGen UID:
381392
Concept ID:
C1854301
Finding
A type of Developmental delay characterized by a delay in acquiring motor skills.
Hypotonia
MedGen UID:
10133
Concept ID:
C0026827
Finding
Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist.
Gowers sign
MedGen UID:
65865
Concept ID:
C0234182
Finding
A phenomenon whereby patients are not able to stand up without the use of the hands owing to weakness of the proximal muscles of the lower limbs.
Neck muscle weakness
MedGen UID:
66808
Concept ID:
C0240479
Finding
Decreased strength of the neck musculature.
Difficulty walking
MedGen UID:
86319
Concept ID:
C0311394
Finding
Reduced ability to walk (ambulate).
Flexion contracture
MedGen UID:
83069
Concept ID:
C0333068
Anatomical Abnormality
A flexion contracture is a bent (flexed) joint that cannot be straightened actively or passively. It is thus a chronic loss of joint motion due to structural changes in muscle, tendons, ligaments, or skin that prevents normal movement of joints.
Skeletal muscle atrophy
MedGen UID:
892680
Concept ID:
C0541794
Pathologic Function
The presence of skeletal muscular atrophy (which is also known as amyotrophy).
Kyphoscoliosis
MedGen UID:
154361
Concept ID:
C0575158
Anatomical Abnormality
An abnormal curvature of the spine in both a coronal (lateral) and sagittal (back-to-front) plane.
Facial diplegia
MedGen UID:
322796
Concept ID:
C1836003
Finding
Facial diplegia refers to bilateral facial palsy (bilateral facial palsy is much rarer than unilateral facial palsy).
Type 1 muscle fiber predominance
MedGen UID:
344274
Concept ID:
C1854387
Finding
An abnormal predominance of type I muscle fibers (in general, this feature can only be observed on muscle biopsy).
Generalized hypotonia
MedGen UID:
346841
Concept ID:
C1858120
Finding
Generalized muscular hypotonia (abnormally low muscle tone).
Nemaline bodies
MedGen UID:
814369
Concept ID:
C3808039
Finding
Nemaline rods are abnormal bodies that can occur in skeletal muscle fibers. The rods can be observed on histological analysis of muscle biopsy tissue or upon electron microscopy, where they appear either as extensions of sarcomeric Z-lines, in random array without obvious attachment to Z-lines (often in areas devoid of sarcomeres) or in large clusters localized at the sarcolemma or intermyofibrillar spaces.
Reduced vital capacity
MedGen UID:
141657
Concept ID:
C0476408
Finding
An abnormal reduction on the vital capacity, which is defined as the total lung capacity (volume of air in the lungs at maximal inflation) less the residual volume (i.e., volume of air in the lungs following maximal exhalation) of the lung.
High palate
MedGen UID:
66814
Concept ID:
C0240635
Congenital Abnormality
Height of the palate more than 2 SD above the mean (objective) or palatal height at the level of the first permanent molar more than twice the height of the teeth (subjective).
Myopathic facies
MedGen UID:
90695
Concept ID:
C0332615
Finding
A facial appearance characteristic of myopathic conditions. The face appears expressionless with sunken cheeks, bilateral ptosis, and inability to elevate the corners of the mouth, due to muscle weakness.

Professional guidelines

Curated

Nowak KJ, Davis MR, Wallgren-Pettersson C, Lamont PJ, Laing NG
Eur J Hum Genet 2012 Jun;20(6) Epub 2012 Apr 18 doi: 10.1038/ejhg.2012.70. PMID: 22510848Free PMC Article

Recent clinical studies

Diagnosis

Tanboon J, Hayashi YK, Nishino I, Sangruchi T
Neuropathology 2015 Feb;35(1):91-3. Epub 2014 Aug 28 doi: 10.1111/neup.12147. PMID: 25168271

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