NEMALINE ROD MYOPATHY
 
PEDBASE.org - The Pediatric Database - Detailed information of NEMALINE ROD MYOPATHY

 

NEMALINE ROD MYOPATHY

 

DEFINITION:

A congenital myopathy characterized by generalized hypotonia, muscle weakness, and nemaline rods on muscle biopsy.

EPIDEMIOLOGY:

  • incidence: ?
  • age of onset:
    • newborn
  • risk factors:
    • familial - autosomal dominant with incomplete penetrance in most cases; autosomal recessive and x-linked dominant forms are more rare
      • chrom.#: 1q21-q23
      • gene: ?
    • F >> M

PATHOGENESIS:

1. Genetic Defect

  • genetic defect -> ? dipeptidyl-peptidase I deficiency (a protease which modifies proteins within the Z-band) -> accumulation of nemaline rods -> hypotonia and muscle weakness

PATHOLOGY:

1. Muscle Biopsy

1. Nemaline Rods

  • rod-shaped inclusion bodies in skeletal muscles
  • consists of Z-band material
    • consists of alpha-actinin and desmin
  • seen on EM and special stains of LM (red staining rods with trichrome)
  • can be seen as an unusual reaction to muscle injury in normal muscles

2. Other

  • type 1 predominance with type 2 absent or sparse
  • focal myofibrillar degeneration

TYPES:

  • 1. Infantile - mild (Congenital non- or slowly-progressive myopathy)
  • 2. Infantile - severe (Congenital rapidly fatal myopathy)
  • 3. Juvenile - mild (Adult onset myopathy)

    • CLINICAL FEATURES:

    1. Neurological Manifestations

    1. Infantile - Mild

    • most common type
    • onset in infancy
    • mild infantile hypotonia and weakness
      • proximal > distal muscles
      • muscles innervated by the cranial nerves
        • facial, masticatory
      • muscle atrophy of both proximal and distal muscles
      • gross motor developmental delay
      • absent or decreased deep tendon reflexes

    2. Infantile - Severe

    • less common
    • onset in infancy
    • severe infantile hypotonia and weakness
      • little spontaneous motor activity
      • intercostal and diaphragmatic muscle weakness requiring respiratory support and inability to clear secretions -> recurrent pneumonias and death
      • absent deep tendon reflexes and Moro

    3. Juvenile

    • onset in adolescence -> early adult
    • mild muscle weakness
      • nonprogressive
      • scapuloperoneal weakness with foot drop
      • patients usually remain ambulatory

    2. Musculoskeletal Manifestations

    1. Dysmorphic Features

    • dolichocephalic-shaped head
    • high-arched palate or cleft palate

    2. Skeletal Features

    • kyphosis
    • lordosis
    • pes cavus
    • pectus excavatum
    • scoliosis
    • talipes equinovarus

    3. Others

    • cardiomyopathy in Juvenile type and rare in others
    • hypermobility of joints
    • chronic lung disease -> cor pulmonale

    INVESTIGATIONS:

    1. Serum

    • normal CPK

    2. EMG

    • myopathy - brief duration, small amplitude abundant polyphasic motor unit potentials

    MANAGEMENT:

    1. Supportive

    • multidisciplinary approach
      • Paediatrics - promote ambulation and physiotherapy, moniter deformities and cardiomyopathy
      • Surgery - moniter and correct deformities, G-tube
      • Genetics - genetic couselling, prenatal diagnosis

     

    Pediatric Database - NEMALINE ROD MYOPATHY

     

    Pediatric Organization - Pedbase [at] Gmail.com

     
    1994 -2007 Pedbase.org 

    Powered by Database of Pediatrics- NEMALINE ROD MYOPATHY