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  1. 1 vaccine induced primary anhidrosis. What would an MRI-PET scan with glucose radio tracer expect to show + a private exchange
  2. 2 Wouldn't FDG-PET show hypometabolism of eccrine glands rather than hypermetabolism? + a private exchange
  3. 3 What PET tracer or higher-resolution imaging could target eccrine glands? + a private exchange
  4. 4 ok, from the formally identified autonomic symptoms described, what would show on PET-MRI, and if not this test, what is the next best line of investigation + a private exchange
  5. 5 which functional immunology assays should now be performed
  6. 6 How appropriate would it be to characterise this as just POTS
  7. 7 So if the anhidrosis and the immunology findings demand a broader autonomic-neuimmune workup, what would one include in that neuroimmune workup?

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So if the anhidrosis and the immunology findings demand a broader autonomic-neuimmune workup, what would one include in that neuroimmune workup?

Oct 15, 2026 · 12 sources used · OpenNeedle synthesis
The workup should map the whole autonomic axis, hunt for an immune cause, and exclude the genetic mimics — the records give you the test sensitivities, but the anhidrosis-specific layer is not in this retrieval.

The core is autonomic function testing. Sudomotor testing is the most sensitive limb: in one series of 125 distal small-fiber neuropathy patients, 98% had some sweating abnormality on thermoregulatory sweat test, with 74 abnormal on QSART (a test that stimulates sweat glands directly to see if the reflex pathway or the gland itself is at fault) [5]. In distal small-fiber neuropathy, QSART was abnormal in 80%, thermoregulatory sweat test in 72%, but cardiac autonomic tests in only 28% [6] — so a normal tilt-table or HRV test does not clear the autonomic nervous system. Combine QST and QSART and diagnostic sensitivity reaches 85% versus 75% and 46% alone [9]. Pinprick loss on exam predicts lab-confirmed small-fiber neuropathy with a positive predictive value of 0.89 [9].

Then confirm structure: skin biopsy for epidermal nerve fiber density is the gold standard, with sensitivity of 74–87% [3], and it outperformed QSART and QST in the largest prospective comparison [3]. Ask for proximal plus distal biopsies — non-length-dependent patterns suggest a ganglionopathy (injury at the nerve-cell body cluster) rather than a stocking-glove neuropathy, and that pattern carries a different differential [7].

Then the immune hunt. Immune-mediated conditions — lupus, Sjögren's, sarcoidosis, connective tissue disease — cluster in non-length-dependent small-fiber neuropathy (14.3% vs 3.4% in length-dependent cases) [4], and SLE itself can produce autonomic neuropathy with axonal degeneration on nerve biopsy [1]. So: full autoimmune serology, Sjögren workup including possible minor salivary gland biopsy, and consider a therapeutic IVIG trial as a diagnostic probe — four idiopathic small-fiber neuropathy patients given IVIG had near or partial resolution [6], and a Sjögren-associated case went from pain score 8 to 0 over three cycles [8]. Response itself is evidence of an immune mechanism.

Exclude mimics: genetic testing for sodium channel mutations (SCN9A, SCN10A, SCN11A) — found in roughly 29%, 9%, and 3.5% of respective idiopathic painful small-fiber neuropathy cohorts [4] — and, if anhidrosis dates to childhood with pain insensitivity or fever, NTRK1 testing for hereditary sensory and autonomic neuropathy type IV [2]. Also an oral glucose tolerance test: glucose dysmetabolism was present in about a third of length-dependent small-fiber neuropathy cases [4].

Retrieval gap, stated plainly: nothing here covers vaccine-specific autoantibody panels or anhidrosis-localization protocols (sweat gland versus preganglionic versus postganglionic), so those steps are general clinical knowledge, not record-backed. The vaccine-autonomic link itself rests on case reports and one pediatric cohort showing standing heart-rate rise and reduced vagal tone after COVID infection or vaccination [10][11][12] — temporally plausible, causally unproven.

My call: a layered workup — full sudomotor and cardiovagal autonomic testing, proximal and distal skin biopsy, comprehensive autoimmune and Sjögren screen, sodium-channel and NTRK1 genetics, glucose tolerance — with IVIG response as a legitimate diagnostic signal. Confidence: moderate; the test-performance numbers are solid, the vaccine-causation layer is not.

Keep digging

Sources used 12

  1. PERIPHERAL SENSORIMOTOR AND AUTONOMIC NEUROPATHY ASSOCIATED WITH SYSTEMIC LUPUS ERYTHEMATOSUS Brain (1987) Thin

    This study investigates the clinical, pathological, and immunological features of peripheral sensorimotor and autonomic neuropathy in patients with systemic lupus erythematosus (SLE), revealing significant axonal degeneration and vasculitis in nerve biopsies.

    DOI: 10.1093/brain/110.2.533
  2. Exome sequencing identifies novel NTRK1 mutations in patients with HSAN‐IV phenotype American Journal of Medical Genetics Part A (2017) Thin

    This study identifies novel mutations in the NTRK1 gene associated with hereditary sensory and autonomic neuropathy type IV (HSAN-IV) in nine patients from unrelated families, expanding the mutational spectrum and providing insights for clinical diagnosis.

    DOI: 10.1002/ajmg.a.38120
  3. Small‐fiber neuropathy Muscle & Nerve (2002) narrative review Strong

    This is a narrative review of small-fiber neuropathy (SFN) summarizing clinical features, diagnostic methods including epidermal nerve fiber density and sudomotor/QST/cardiovagal tests with sensitivities ranging 59-88%, known causes, and symptomatic treatments. No original patie…

    DOI: 10.1002/mus.10181
  4. Small Fiber Neuropathy Seminars in Neurology (2019) narrative review Strong

    This is a clinical review article summarizing the clinical features, diagnostic evaluation, associated conditions, and management of small fiber neuropathy (SFN), emphasizing skin biopsy with intraepidermal nerve fiber density (IENFD) evaluation as the gold standard for diagnosi…

    DOI: 10.1055/s-0039-1688977
  5. Detection of small‐fiber neuropathy by sudomotor testing Muscle & Nerve (2006) Thin

    This study investigates the relationship between sudomotor function and distal small-fiber neuropathy (DSFN), revealing that sudomotor testing is a highly sensitive tool for detecting autonomic involvement in patients with DSFN, with 98% showing some level of sweating abnormalit…

    DOI: 10.1002/mus.20551
  6. Review: Small-Fiber Neuropathy The Neurologist (2002) narrative review Strong

    Small-fiber neuropathies are heterogeneous disorders causing pain, temperature loss, and autonomic dysfunction; routine nerve conductions and EMG are often normal, so diagnosis relies on specialized tests and treatment is largely symptomatic.

    DOI: 10.1097/00127893-200207000-00004
  7. Non‐length‐dependent small fiber neuropathy: Not a matter of stockings and gloves Muscle & Nerve (2021) Thin

    A comprehensive narrative review detailing non-length-dependent small fiber neuropathy (NLD-SFN): its definition, ganglionopathy-like pathophysiology, clinical features, associated conditions, diagnostic approaches (skin biopsy IENFD, QST, autonomic testing, CCM, MRI), and curre…

    DOI: 10.1002/mus.27379
  8. Extreme efficacy of intravenous immunoglobulin therapy for severe burning pain in a patient with small fiber neuropathy associated with primary Sjögren’s syndrome Modern Rheumatology (2009) Thin

    This study presents a case of a 40-year-old woman with small fiber neuropathy associated with primary Sjögren's syndrome who experienced immediate and significant relief from severe burning pain following intravenous immunoglobulin therapy, suggesting an immune-mediated mechanis…

    DOI: 10.3109/s10165-009-0180-2
  9. Diagnostic Criteria for Small Fiber Neuropathy Journal of Clinical Neuromuscular Disease (2017) primary study Strong

    In a retrospective review of 56 SFN patients, combining clinical examination with QST and QSART improved diagnostic sensitivity (85%) over single modalities, prompting proposed definite, probable, and possible diagnostic criteria.

    DOI: 10.1097/cnd.0000000000000154
  10. COVID-19 Vaccination Might Induce Postural Orthostatic Tachycardia Syndrome: A Case Report Vaccines (2022) Thin

    This case report describes a 46-year-old female who developed new-onset postural orthostatic tachycardia syndrome (POTS) following her first dose of the BNT162b2 (Pfizer-BioNTech) COVID-19 vaccine, highlighting the need for further research into vaccine-related autonomic dysfunc…

    DOI: 10.3390/vaccines10070991
  11. Dysautonomia in Children with Post-Acute Sequelae of Coronavirus 2019 Disease and/or Vaccination Vaccines (2022) primary study Strong

    Children and young adults with post-COVID-19 or post-vaccination health problems show elevated heart rate, increased heart rate increase during standing, raised stress index, and reduced pNN20 values compared with healthy controls, consistent with dysautonomia.

    DOI: 10.3390/vaccines10101686
  12. Postural orthostatic tachycardia syndrome after mRNA COVID-19 vaccine Clinical Autonomic Research (2022) Thin

    This study reports five cases of postural orthostatic tachycardia syndrome (POTS) that developed in patients after receiving mRNA COVID-19 vaccines, highlighting the need for further investigation into the association between vaccination and autonomic disorders.

    DOI: 10.1007/s10286-022-00880-3

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