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Difficulty: HardNeoplastic Processes

Match each clinical presentation of a paraneoplastic syndrome with its specific underlying pathophysiologic mechanism.

  • A 64-year-old male with a central lung mass develops symmetric proximal muscle weakness that paradoxically improves following brief periods of repetitive exertion.Elaboration of autoantibodies that cross-react with presynaptic voltage-gated calcium channels, impairing acetylcholine release.
  • A 58-year-old female with a newly diagnosed solid renal mass presents with an asymptomatic elevation in hemoglobin (18.5 g/dL) and normal arterial oxygen tension.Ectopic, autonomous synthesis of erythropoietin by malignant cells, functioning independently of renal tissue hypoxia.
  • A 71-year-old male with early satiety and weight loss rapidly develops dozens of intensely pruritic, stuck-on pigmented papules across his trunk.Paraneoplastic production of cytokines, such as transforming growth factor-alpha (TGF-α), driving rapid epidermal hyperproliferation.
  • A 66-year-old male with a neuroendocrine lung tumor presents with lethargy, a serum sodium of 118 mEq/L, and inappropriately concentrated urine.Ectopic synthesis of a nonapeptide hormone that binds V2 receptors in the renal collecting duct, driving aquaporin-mediated water retention.
  • A 52-year-old female with a cystic adnexal mass presents with acute psychiatric disturbances, memory deficits, and choreiform movements.Production of autoantibodies directed against the NR1 subunit of the NMDA receptor, often triggered by ectopic neural tissue.

Answer

Lambert-Eaton syndrome matches with presynaptic calcium channel antibodies; Paraneoplastic polycythemia matches with ectopic erythropoietin; Leser-Trélat sign matches with TGF-alpha production; SIADH matches with ectopic ADH; Anti-NMDA receptor encephalitis matches with NR1 subunit antibodies.
Each clinical scenario describes a specific paraneoplastic syndrome whose underlying molecular pathogenesis directly correlates with the accurately matched humoral or autoimmune process.

Step-by-Step Solution

1
Analyze the presentation of proximal weakness improving with use in the setting of a central lung mass.
Identify Lambert-Eaton myasthenic syndrome.
This syndrome is mediated by autoantibodies against presynaptic voltage-gated calcium channels, which differentiate it from myasthenia gravis.
2
Analyze the presentation of erythrocytosis with normal oxygenation and a renal mass.
Identify paraneoplastic polycythemia secondary to renal cell carcinoma.
This is driven by the ectopic, hypoxia-independent production of erythropoietin by the malignant cells.
3
Analyze the rapid appearance of seborrheic keratoses alongside gastrointestinal symptoms.
Identify the sign of Leser-Trélat.
The sudden cutaneous eruption is driven by tumor-secreted cytokines and growth factors, notably transforming growth factor-alpha (TGF-α).
4
Analyze the hyponatremia with concentrated urine in the setting of a neuroendocrine lung tumor.
Identify the Syndrome of Inappropriate Antidiuretic Hormone secretion (SIADH).
Small cell lung cancer can ectopically secrete ADH (a nonapeptide hormone), leading to unregulated free water retention at the collecting ducts.
5
Analyze the psychiatric changes and choreiform movements associated with a cystic adnexal mass.
Identify anti-NMDA receptor encephalitis.
This condition is classically associated with ovarian teratomas and is caused by autoantibodies cross-reacting with the NR1 subunit of NMDA receptors.

Key Concept

Paraneoplastic syndromes are systemic clinical disorders associated with malignancies that are mediated by tumor-secreted hormones, cytokines, or cross-reacting autoantibodies, rather than the physical mass of the primary tumor or its metastases.
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Topics

Neoplastic Processes

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