ZSFG AM Report Pearls 2/12/18: I Get So Weak In My Knees, I Can Hardly Breathe: Paraneoplastic Muscle Function Syndromes

Thank you to Vhaibhav for presenting a really interesting case of a patient with progressive proximal muscle weakness and tenderness to palpation found to have a significantly elevated CK, who subsequently developed white out of the left lung. We discussed several teaching points outlined below. While it is unclear if there is an endobronchial lesion, let’s review some of the paraneoplastic processes that could occur.

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DDx for Lung White Out:

White Out of Lung:

  • Trachea deviated to side of white out => Collapsed Lung (Lung tissue compressed pulling over the trachea and right heart border)
  • Trachea deviated to side opposite of white out => Something Filling Chest Cavity (Blood, Fluid, Pus)

 

Paraneoplastic Syndromes Affecting Muscles:

Category Disease Name Antibody Associated Cancer Clinical
Neuromuscular Myasthenia Gravis AChR Antibody

Anti-MuSk

Thymic hyperplasia (more rarely SCLC, thyroid CA, breast CA, Hodgkin lymphoma) Often with ocular symptoms, weakness of eyelids or extraocular muscles (ptosis, diplopia), fluctuating skeletal muscle weakness
  Lambert-Eaton Myasthenic Syndrome (LEMS) Antibody against voltage-gated calcium channels SCLC Often starting with hip girdle weakness. Less dramatically shoulder girdle weakness, progress in caudocranial direction, assoc with decreased/absent reflexes
Inflammatory Myopathies Dermatomyositis and polymyositis Myositis-specific antibodies (i.e. myositis panel) CA of breast, lung, ovary, stomach, NHL Proximal skeletal muscle weakness, Gottron’s papules (among many other signs/symptoms)
Peripheral Nerve Hyperexcitability Paraneoplastic Neueromyotonia Anti-LGI1 Thymoma, SCLC, Hodgkin lymphoma Muscle stiffness caused by continuous muscle fiber activity, muscle cramps, twitching, spasm, stiffness, carpopedal spasm
Necrotizing Myopathy Acute Necrotizing Myopathy Anti-SRP, Anti-HMGCR Tumors of lung, breast, GI tract Symmetric, painful, predominantly proximal weakness leading to severe disability over 1-2 months

Song Credit: SWV – “Weak” – https://youtu.be/976b8TPPFJU

Sources:

  • Darnell RB & Posner, JB (2003). Paraneoplastic syndromes involving the nervous system. NEJM 349:153-1554.

Evernote:

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