| Myotonia Congenita (MC) (Two forms: Thomsen's and
Becker's Disease) |
| Onset: |
Infancy to childhood. |
| Symptoms: |
Muscle stiffness and cramps usually occurring after periods of rest. With
activity, returns to normal muscle function. |
| Progression: |
Condition causes discomfort but is not life-threatening. |
| Inheritance: |
Autosomal dominant, autosomal recessive. |
| Paramyotonia Congenita (PC) |
| Onset: |
Childhood to early adulthood. |
| Symptoms: |
Poor or difficult relaxation of muscles, which may worsen after repeated
use or exercise. Often may be associated with hyperkalemic periodic paralysis. |
| Progression: |
Condition causes discomfort throughout life but is not life-threatening. |
| Inheritance: |
Autosomal dominant. |
| Central Core Disease (CCD) |
| Onset: |
Early infancy to childhood. |
| Symptoms: |
Delayed motor development. Hip displacement at birth not uncommon. |
| Progression: |
Variable severity and progression. May be disabling. |
| Inheritance: |
Autosomal dominant. |
| Nemaline Myopathy (NM) |
| Onset: |
Early childhood. |
| Symptoms: |
Delayed motor development. Weakness of arm, leg, trunk, face and throat
muscles. |
| Progression: |
Severity and progression vary. Life expectancy is threatened. |
| Inheritance: |
Autosomal dominant, autosomal recessive. |
Myotubular Myopathy
(MTM or MM) |
| Onset: |
Infancy. |
| Symptoms: |
Drooping of upper eyelids, facial weakness, blackout spells. Weakness
of the limbs and trunk muscles. Reflexes usually absent. |
| Progression: |
Slow progression. |
| Inheritance: |
X-linked recessive, autosomal recessive, autosomal dominant. |
| Periodic Paralysis (PP) (Two forms:
Hypokalemic - HYPOP - and Hyperkalemic - HYPP) |
| Onset: |
Childhood to adulthood. |
| Symptoms: |
Episodes of generalized muscle weakness with periods of paralysis affecting
arms, legs and neck. Hyperkalemic type may be associated with paramyotonia
congenita. |
| Progression: |
Frequency of attacks and severity vary. May respond to drug therapy. |
| Inheritance: |
Autosomal dominant. |
