Case Presentation:

A 12 year-old boy was admitted for a 9-month history of pain and 30-pound weight loss. Nine months prior to presentation, this previously well boy developed panic attacks, insomnia, anorexia, intermittent vomiting, and generalized body pain that affected ambulation. He was diagnosed with depression, anxiety, and ADHD. Multiple medication and behavior interventions failed to alleviate symptoms. Two admissions at different hospitals resulted in discharge diagnoses of somatic pain disorder and hypertension. 

On admission to our hospital, the patient was persistently tachycardic and hypertensive. 24-hour urine metanephrines and catecholamines and plasma metanephrines were elevated. Radiologic evaluation for pheochromocytoma and paraganglioma, including MIBG, PET scan, and MRI of the head, neck, chest, spine, and pelvis was unremarkable. An extensive laboratory evaluation was performed considering a broad differential for diffuse body pain and sympathetic overdrive (hypertension, tachycardia, and weight loss).

On hospital day 26, a serum autoimmune paraneoplastic panel revealed autoantibodies to voltage-gated potassium channels (VGKC). Intravenous immune globulin (IVIG) (2 g/kg) was given over 3 days, followed by 3 days of methylprednisolone. Marked symptom improvement was noted after the first IVIG dose.  He was discharged on hospital day 33 after continued rapid improvement, including consuming more than 2000 oral kcal/day, minimal pain, improved ambulation, and resolved tachycardia. Plasma metanephrines checked at discharge were normal. Two months later, repeat serum paraneoplastic panel was negative for autoantibodies to VGKC, anti-hypertensive medication had been discontinued, the patient’s weight was at the 35thpercentile, and he had resumed normal activity.

Discussion:

  • VGKC antibodies are associated with a range of neurologic presentations, including central, peripheral, and autonomic dysfunction.
  • This is the first description of VGKC auto-antibodies associated with hypertension and tachycardia in the setting of elevated catecholamines.
  • Etiology of these antibodies is unclear and specificity of the VGKC for specific disease states remains controversial.
  • Given rapid resolution of all clinical symptoms and resolution of serum antibodies after immunotherapy, it is likely that the VGKC antibody was pathogenic in our patient.

Conclusions:

We present an unusual case of VGKC autoimmunity in a 12 year-old boy with elevated catecholamines, hypertension, tachycardia, diffuse pain, anorexia, vomiting, and failure to thrive.  VGKC antibodies should be considered as part of the testing in patients presenting with elevated metanephrines and catecholamine secretion, as well as those with chronic pain and other unexplained neurologic symptoms.