Comparison of Skin Biopsy and MIBG-SPECT in Neuropathic POTS (S37.004)

OBJECTIVE: Here, our objective was to evaluate the correlation between C-fiber involvement shown by skin biopsy and adrenergic cardiac MIBG-uptake in a larger cohort of POTS-patients. BACKGROUND: Postural orthostatic tachycardia syndrome (POTS) is a disorder of orthostatic intolerance characterized by excessive tachycardia of unknown etiology. Formerly we demonstrated that myocardial Metaiodobenzylguanidine (MIBG) scintigraphy uptake is markedly decreased in some POTS-patients. It is still unclear whether this partial autonomic dysfunction is functional or anatomic. Epidermal skin biopsy is a useful test for the investigation of small-calibre sensory nerves, including autonomic nerve fibers. Recently, we primary described reduced intraepidermal fiber density (IENF density) in POTS. DESIGN/METHODS: Skin biopsies of 75 patients with POTS (Mean age 29 ± 10 y., 54 females, 21 males) were taken. Protein gene product 9.5 (PGP9.5) immunohistochemistry findings were compared to MIBG myocardial scintigraphy imaging data. The primary endpoint of the study was to evaluate the decrease in the density of small intraepidermal nerve fibers and to correlate small-fiber neuropathy with reduced cardiac MIBG-uptake. RESULTS: Mean IENF density was reduced to 7.5 ± 2.9 /mm (normal range: ≥ 7/mm). Considering individual patients, IENF density was abnormal in 41 %. MIBG-uptake after 5 hours was reduced in 12 % of patients compared to the normal range of the heart-to-mediastinum ratio ≥1.7. Low IENF density correlates with reduced cardiac MIBG uptake (r=0.39, p=0.001, two-tailed). The degree of accordance with both methods was low (Kappa = 0.14). The odds ratio for a pathological finding due to age was 1.09 for IENF density (p=0.001) and 1.02 for MIBG uptake (n.s.). CONCLUSIONS: A subset of neuropathic POTS might harbor small fiber neuropathy with abnormalities of the unmyelinated nerve fibers in the skin and is associated with reduced myocardial postganglionic sympathetic innervation. Skin biopsy is more sensitive to prove for neuropathic POTS than MIBG-SPECT. Disclosure: Dr. Haensch has nothing to disclose. Dr. Isenmann has nothing to disclose. Dr. Tosch has nothing to disclose. Dr. Katona has nothing to disclose. Dr. Weis has nothing to disclose.