When POTS is the tip of the iceberg: Rare cases of dysautonomia as a possible manifestation of another disorder

Postural tachycardia syndrome (POTS) is a heterogenous disorder of the autonomic nervous system that is commonly associated with small fiber neuropathy, Ehlers-Danlos Syndrome and autoimmune disorders, but association with rare conditions may also occur. Reported here are clinical features, diagnostic tests and treatment outcomes of 6 unique patients who presented with POTS and were subsequently diagnosed with Fabry disease, McArdle disease, Complex V mitochondrial disease, carcinoid tumor, Hodgkin's lymphoma and chemotherapy-induced neuropathy. All patients (age range 15-57 years, 3 females, 3 males) presented with orthostatic intolerance of at least 6 months duration, and all patients had co-morbid small fiber neuropathy. Five patients presented with symptoms of POTS months to years before the underlying or associated medical condition was discovered, and three out of six patients experienced either complete resolution or significant improvement of POTS after treatment of the underlying or associated medical condition. In rare cases, POTS can present as a possible manifestation of genetic, neoplastic or neurotoxic disorders. Unusual clinical features that fall outside of the typical spectrum of dysautonomia can point toward the presence of another disorder and help guide further diagnostic investigation.