Peripheral Nerves and Skeletal Muscles

Question 1

Most common chronic acquired peripheral neuropathy; clinical feature is mixed sensorimotor polyneuropathy greater than or equal to 2 months.

Answer 1

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP)

Question 2

Most common inherited peripheral neuropathy; has autosomal dominant (CMT1 and 2) and CMTX (X-linked) forms; CMT2 is an axonal neuropathy that is phenotypically severe and presents early in life.

Answer 2

Charcot-Marie Tooth (CMT) disease

Question 3

Rapidly progressive acute demyelinating disorder affecting motor axons that results in ascending weakness that may lead to death from failure of respiratory muscles over a period of only several days; associated with C. jejuni infection.

Answer 3

Guillain-Barre syndrome

Question 4

The most common form of diabetic neuropathy (DM neuropathy: most common cause of peripheral neuropathy)

Answer 4

Distal symmetric sensorimotor neuropathy

Question 5

Disorder caused by autoantibodies that block the function of postsynaptic acetylcholine receptors at motor end plates, which results in the degradation and depletion of the receptors; clinically presents with fatigable weakness.

Answer 5

Myasthenia gravis

Question 6

Disorder caused by autoantibodies that inhibit the function of presynaptic calcium channels, which reduces the release of acetylcholine into the synaptic cleft; associated with SCLC as paraneoplastic syndrome.

Answer 6

Lambert-Eaton myasthenic syndrome (LEMS)

Question 7

Most common in inflammatory myopathy in children; associated with Gottron papules and heliotrope rash (see Pediatrics); microscopically, it is associated with perivascular mononuclear cell infiltrates, dropout of capillaries, the presence of so-called tubuloreticular inclusions in endothelial cells, and myofiber damage in a paraseptal or perifascicular pattern.

Answer 7

Dermatomyositis

Question 8

Basic difference between dermatomyositis and polymyositis.

Answer 8

Skin changes absent in polymyositis

Question 9

Most common inflammatory myopathy in patients older than 65 years; clinically present with quadriceps and distal upper extremity weakness, with dysphagia.

Answer 9

Inclusion body myositis

Question 10

Disorders caused by mutation in dystrophin gene in X chromosome (Xp21); patients present with weakness at around 5 years of age; pseudohypertrophy of the calf muscles is an important initial physical finding; associated with Gower sign.

Answer 10

Duchenne Muscular Dystrophy (DMD)/Becker Muscular Dystrophy (BMD) (less severe)

Question 11

Differences in dystrophin immunohistochemistry between DMD and BMD.

Answer 11

DMD: Dystrophin(-); BMD: Dystrophin(+) but reduced

Question 12

Mixture of cellular areas (Antoni A) and hypocellular areas in myxoid stroma (Antoni B) with palisading of nuclei and Verocay bodies; Immunohistochemical staining for S-100 is positive; associated with NF type 2.

Answer 12

Schwannoma/Neurilemmoma

Question 13

Tumor composed of Bland Schwann cells with stromal cells (mast cells, perineurial cells, CD34+ spindle cells and fibroblasts) in a loose collagen stroma; associated with NF type 1.

Answer 13

Neurofibroma

Question 14

Most common origin of malignant peripheral nerve sheath tumors.

Answer 14

Malignant transformation of a plexiform neurofibroma

Question 15

Autosomal dominant disorder caused by mutations in the tumor suppressor neurofibromin a tumor suppressor of Ras oncoprotein, encoded on Chromosome 17 (17q11.2); associated with development of neurofibromas, MPNSTs, optic nerve gliomas, other glial tumors and hamartomatous lesions, pheochromocytomas, pigmented iris nodules (Lisch nodules), and cutaneous hyperpigmented macules (axillary freckling and cafe’au lait spots).

Answer 15

Neurofibromatosis Type 1

Question 16

Autosomal dominant disorder caused by mutations in the merlin gene (NF2), a tumor suppressor that facilitates E-cadherin contact inhibition, in Chromosome 22 (Ch22q12); hallmark is bilateral vestibular schwannomas, meningiomas and ependymomas (commonly intraspinal).

Answer 16

Neurofibromatosis Type 2