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Difficulty: Very hardHematology and Oncology

Review the following clinical vignettes describing patients who are experiencing complications related to underlying malignancies. Match each patient's clinical presentation with the primary pathophysiologic mechanism responsible for their symptoms.

  • A 68-year-old man with a newly discovered right hilar mass presents with proximal muscle weakness that transiently improves with repetitive movement, accompanied by dry mouth and absent deep tendon reflexes.Cross-reactivity of tumor-directed autoantibodies with presynaptic voltage-gated calcium channels
  • A 55-year-old woman with a history of treated breast cancer presents with subacute, rapidly progressive truncal ataxia, dysarthria, and multidirectional nystagmus. Brain magnetic resonance imaging reveals no intracranial metastases.Immune-mediated destruction of cerebellar Purkinje cells by onconeural antibodies
  • A 42-year-old man with bulky mediastinal lymphadenopathy, fever, and drenching night sweats develops anasarca. Laboratory studies show a serum albumin of 2.1 g/dL and a 24-hour urine protein of 5.2 g.Release of T-cell-derived cytokines resulting in effacement of glomerular epithelial foot processes
  • A 72-year-old man with an apical lung mass and a 50-pack-year smoking history presents with confusion, polyuria, and abdominal pain. Laboratory evaluation reveals a serum calcium of 14.2 mg/dL and an intact parathyroid hormone of 5 pg/mL.Ectopic secretion of a peptide that binds to and activates osteoblast parathyroid hormone 1 receptors

Answer

Lambert-Eaton syndrome (hilar mass) matches with antibodies against presynaptic calcium channels. Paraneoplastic cerebellar degeneration (breast cancer) matches with immune destruction of Purkinje cells. Minimal change disease (mediastinal mass/Hodgkin lymphoma) matches with cytokine-mediated foot process effacement. Humoral hypercalcemia of malignancy (apical lung mass) matches with ectopic PTHrP secretion.
Each clinical vignette provides a classic presentation of a distinct paraneoplastic syndrome. The first is Lambert-Eaton myasthenic syndrome (LEMS) caused by anti-calcium channel antibodies. The second is paraneoplastic cerebellar degeneration caused by anti-Purkinje cell antibodies. The third is minimal change disease secondary to Hodgkin lymphoma, caused by cytokine-induced podocyte injury. The fourth is humoral hypercalcemia of malignancy caused by tumor secretion of PTHrP.

Step-by-Step Solution

1
Analyze the first vignette to identify the syndrome and its underlying mechanism.
The combination of a central lung mass, proximal muscle weakness improving with use, and autonomic dysfunction indicates Lambert-Eaton myasthenic syndrome, caused by antibodies against presynaptic voltage-gated calcium channels.
Recognizing the classic triad of LEMS and its association with small cell lung cancer is required to identify the molecular mechanism.
2
Analyze the second vignette to identify the syndrome and its underlying mechanism.
Subacute ataxia in a breast cancer patient with a negative brain MRI points to paraneoplastic cerebellar degeneration, which is driven by onconeural antibodies (such as anti-Yo) destroying Purkinje cells.
Ruling out brain metastasis is crucial; the subacute cerebellar presentation in breast cancer is a classic paraneoplastic neurological syndrome.
3
Analyze the third vignette to identify the syndrome and its underlying mechanism.
Mediastinal lymphadenopathy with B symptoms implies Hodgkin lymphoma, and new-onset nephrotic syndrome in this context is almost always minimal change disease caused by T-cell cytokine release effacing podocyte foot processes.
Linking specific malignancies with their associated paraneoplastic glomerulopathies allows identification of the correct pathophysiology.
4
Analyze the fourth vignette to identify the syndrome and its underlying mechanism.
Severe hypercalcemia with suppressed PTH in a smoker with a lung mass indicates squamous cell carcinoma secreting PTH-related peptide (PTHrP), which activates PTH1 receptors.
Differentiating PTH-mediated hypercalcemia from PTHrP-mediated hypercalcemia is essential in oncologic emergencies.

Key Concept

Paraneoplastic syndromes possess specific pathophysiologic mechanisms that must be correlated with their associated underlying malignancies and varied clinical presentations.
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Topics

Hematology and Oncology

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