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Lecture 16
Neuromuscular Pathology
| Question | Answer |
|---|---|
| Clinical features of myopathy | (1)Pure motor involvement (weakness) (2)Proximal weakness (3)Absence of autonomic dysfunction (4)Muscle atrophy (5)Pseudohypertrophy (6)Myotonia (7)Contractures |
| Features of neuropathy | (1)Mixed motor and sensory involvement (2)distal weakness (3)may have some autonomic dysfunction |
| Gene mutated in Duchenne's and Becker muscular dystrophy | DMD gene which encodes a protein called dystrophin is mutated. Most mutations are deletions or duplications of one or more exons in the dystrophin gene, often resulting in a frameshift mutation. |
| What is the inheritance pattern of Duchenne's and Becker muscular dystrophy? | X-linked inheritance. DMD gene is found on the X chromosome. |
| A myopathy that typically manifests by 5 years of age with weakness and evetually wheelchair dependence by age of 10-12. Death occurs due to respriatory insufficiency and cardiac failure by the early 20s. | Duchenne's muscular dystrophy |
| Myopathy associated with mutation of sarcoglycans | Limb girdle dystrophies |
| Myopathy associated with mutation of merosin (laminin-2) | Congential muscular dystrophy |
| Components of dystrophin complex | (1)Dystrophin (2)4 different sarcoglycans (3)laminin-2 |
| Most common adult-onset muscular dystrophy | Myotonic dystrophy |
| Inheritance pattern of myotonic dystrophy | Autosomal dominant |
| Genetic abnormality causing myotonic dystrophy | Trinucleotide repeat expansion (CTS) in 3'UTR of myotonin kinase. (<30 repeats is normal, >50 repeats results in disease) |
| An inflammatory myopathy with skin manifestations | Dermatomyositis |
| Pathogenesis of dermatomyositis | Immune complexes deposit in capillaries of muscle and skin.These damaged capillaries cause ischemic damage, especially at periphery. |
| A chronic inflammatory myopathy characterized by proximal muscle weakness and a higher incidence in females. This condition is responsive to steroid treatment. | Polymyositis |
| A chronic inflammatory myositis with a higher incidence in males with typical distal muscle involvement. Histologic features include rimmed vacuoles and/or inclusions. This condition is not responsive to steroid treatments. | Inclusion body myositis |
| Enzyme deficient in Mcardle's disease | Phosphorylase |
| Inheritence pattern of Mcardle's disease | Recessive inheritance |
| Clinical features of Mcardle's disease | (1)Onset age <15 (2)male predominance (3)exercise intolerance (especially brief and intense (4)muscle cramping (5)muscle swelling |
| Enzyme deficient in Pompe's disease | Acid maltase deficiency |
| Inheritance pattern of Pompe's disease | Recessive inheritance |
| What are the 3 types of Pompe's disease | (1)Infantile onset (2)Childhood onset (3)Adult onset |
| What variant of Pompe's disease with involvement of liver and heart, causing cardiomegaly and congestive heart failure. Death usually occur by 1 year of age. | Infantile onset Pompe's disease |
| What variant of Pompe's disease is characterized by proximal muscle weakness with involvement of mainly the large muscles. Glycogen accumulation is mainly limited to the muscle. | Childhood onset Pompe's disease |
| Myopathy due to genetic defects in enzymes for fatty acid transport into mitochondria or fatty acid oxidation | Lipid storage myopathies |
| Myopathy present in young adulthood with opthalmoplegia plus pigmentary degeneration of the retina | Kearns-Sayre syndrome |
| (T or F)Mutations in only mitochondrial genes cause mitochondrial myopathy. | False. Mutations in both nuclear and miotchondrial genes cause mitochondrial myopathies. |
| Inheritance pattern of mitochondrial myopathies | Maternal inheritance, since the oocyte contrbiutes the mitochondria to the embryo |
| An autoimmune disease with antibodies against acetylcholine receptors. | Myasthenia gravis |
| An autoimmune disease with anti-presynaptic calcium channel antibodies. The autoantibodies are usually a paraneoplastic syndrome. | Eaton-Lambert Syndrome |
| Symptoms of peripheral neuropathies | (1)Weakness (2)Sensory loss (3)Dysesthesias |
| Signs of peripheral neuropathies | (1)muscle atrophy (2)lower motor neuron signs (3)loss of tendon reflexes |
| Wallerian degeneration | Peripheral nerve reaction to injury characterized by acute degeneration of an axon and its myelin sheath distal to the site of injury. |
| Regnerating clusters | Evidence of peripheral nerve axonal damage characterized by several adjacent sprouting axons myelinated by a single Schwann cell, different than normal 1:1 relationship of Schwann cell to axon. |
| (T or F) Peripheral nerves can regenerate if the scaffolding of the nerve is intact. | True. |
| Onion bulb formation | Response of Schwann cells to any chronic demyelinating process, with repeated rounds of demyelination/remyelination. |
| Treatment for Guillain-Barre Syndrome | Supportive therapy and plasma exchange or IV IgG |
| An acute onset neuropathy that may precede with Campylobacter jejuni infection and may result in respiratory failure. | Guillain-Barre syndrome |
| Histologic features of chronic inflammatory demyelinating polyneuropathy | Lymphocytic and macrophage infiltrates in early phases and onion bulbs in the end-stage of the disease |
| What is the morphologic features of diabetic neuropathy | (1)Axonal loss of motor and sensory nerves (2)Axonal regeneration (3)Thickened capillary walls (4)Hyalinization of capillary walls |
| Most common form of diabetic neuropathy | Diatal, sensory polyneuropathy in a glove and stocking pattern |
| What type of neuromuscular is characterized by decreased nerve conduction velocities and large compound muscle action potentials on nerve conduction studies? | Neurogenic (nerve or spinal) disorder |
| What type of neuromuscular disorder is characterized by high spontaneous motor unit activity on EMG? | Inflammatory myopathy |
| Neuropathy characterized by asthma and progressive weakness | Churg-Strauss Vasculitis |
| Function of connexin 32 | Forms gap junctions between cells of PNS myelin |
| What neuropathy is caused by a point mutation in connexin 32? | Charcot-Marie Tooth Neuropathy |
| What is the inheritance pattern of Charcot-Marie Tooth Neuropathy | X-linked dominant inheritance |
| What neuropathy is caused by gene duplication of PMP-22? | Charcot-Marie Tooth Neuropathy 1A |
| What neuropathy is caused by gene deletion of PMP-22? | Hereditary Neuropathy with Pressure Palsies |
| Hereditary neuropathy characterized by nerve paresis following compression or mild trauma. | Hereditary Neuropathy with Pressure Palsies |
| What is the inheritance pattern of Hereditary Neuropathy with Pressure Palsies? | Autosomal dominant |
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