<span class="center-menu">← <small>PREVIOUS: [[5.3. Neuropathic POTS (associated with small fiber neuropathy)]]</small> | <small>NEXT: [[6. Management and Treatment Strategies]]</small> →</span> -------- ##### Summary >[!Summary] >- some refractory cases of POTS are due to underlying illness driving the symptoms. If these are not addressed then POTS symptoms may continue or worsen despite standard therapy[[#^5]] >- 40% of patients with chronic fatigue syndrome have POTS[[#^3]] >- some hyperadrenergic POTS patients have mast cell activation disorder. it is unknown whether sympathetic stimulation in these patients induces mast cell degranulation or whether primary mast cell activation causes release of vasodilators and compensatory sympathetic activation[[#^3]] >- postural tachycardia ± syncope can be present in several disorders. some patients with CFS have orthostatic intolerance with tilt-induced syncope[[#^2]] -------- >_“Functional gastrointestinal disorders associated with poor water intake due to nausea or excess fluid loss due to diarrhea may result in hypovolemia with secondary orthostatic symptoms and tachycardia.”_ <small>([[Benarroch-2012]], [p. 3](zotero://open-pdf/library/items/WEZLT9QC?page=3&annotation=PA2GQ6QB))</small>^1 >*“Postural tachycardia ± syncope can be present in several of the disorders. Some patients with chronic fatigue syndrome have orthostatic intolerance with tilt-induced syncope, and a subset will respond to treatment directed at syncope.” *<small>([[Low-2009]], [p. 2](zotero://open-pdf/library/items/I4WAD8AG?page=2&annotation=X2VYPQ74))</small>^2 >*“40% of patients with chronic fatigue syndrome have POTS” *<small>([[Low-2009]], [p. 2](zotero://open-pdf/library/items/I4WAD8AG?page=2&annotation=6B4GIPDX))</small>^3 >*“Some POTS patients present with severe flushing in addition to their tachycardia and have an associated mast cell activation disorder. These patients often have a hyperadrenergic <small>([p. 7](zotero://open-pdf/library/items/CAWTWYLR?page=7&annotation=YN6J6IBU))</small> phenotype, with both orthostatic tachycardia and hypertension in the upright position, as well as dyspnea, headache, lightheadedness, chest discomfort, and gastrointestinal symptoms. It is unknown whether sympathetic stimulation in these patients induces mast cell degranulation or whether primary mast cell activation causes release of vasodilators and compensatory sympathetic activation [56]. This diagnosis is most often made with an elevated histamine metabolite (>230 μg methylhistamine/g creatinine) in a 4h urine sample started at the onset of a severe flushing spell.” *<small>([[Garland-2015]], [p. 8](zotero://open-pdf/library/items/CAWTWYLR?page=8&annotation=AZRLQ6ZA))</small>*^4 >*“Some refractory cases of POTS are due to underlying illness driving the symptoms. If these are not addressed than POTS symptoms may continue or worsen despite standard therapy.”* <small>([[Miller-2018]], [p. 7](zotero://open-pdf/library/items/A3CIPE3G?page=7&annotation=JBP5AAD3))</small>^5