PFS & Small Fiber Neuropathy

Very long post! All I ask is that if you’re going to participate in the discussion, please keep it on topic to SFN and read the whole thing!

My story with PFS is like many here, except for one key difference - I have a diagnosis of non-length dependent (equally distributed) idiopathic (they don’t have a cause) small-fiber neuropathy.

My story

I took the drug for 7 weeks in 2018, from Mar 15 to May 7. Within just a few weeks I experienced a significant testicular atrophy. Somehow I didn’t think much of this and continued taking the drug, assuming that if it was this obvious, it must be a common side effect. My doctor assured me it would return. Around week 6 I started to be bothered that there was no change. I also noticed my penis was perpetually in a ‘non-aroused’, sort of shrunken state. This was all weird enough for me and I quit the drug the next week.

Around 6 weeks later, I noticed a bizarre feeling of numbness on my stomach and face. This persisted, and slowly worsened. I felt it extend across my body, arms, down the tip of my nose, etc. All at once it felt like the sensuality was disappearing from my touch. I could still feel light touch, but it had no emotional resonance.

Now I was genuinely freaked out. I became very anxious and over the coming months, as the numb sensation progressed, deeply depressed. This depression was reinforced by each doctor who ignored my symptoms, including endocrinologists, dermatologists, urologists, and most importantly, 2 neurologists. Throughout I never lost the ability to perform sexually, which I realize is inconsistent with the typical presentation, but I do attribute my loss of libido and period of lack of spontaneous erections mainly to my drug-induced and also circumstantial depression.

(One quick aside, though I experienced the clinical loss of sensation later, I have some subtle hints that it was occurring sub-clinically while I was on the drug - namely, I was having sex with someone I hadn’t been with in almost a year, and I actually remember thinking, which seemed very odd at the time - why does her vagina not feel as good? Do I not like her as much?)

My first indication that something was provably wrong was a visit to Goldstein. Although my general opinion of the experience was low, he performed what’s called “Quantitative Sensory Testing”, basically, they vibrate a device on your skin and you mark the point at which you can no longer feel the vibration. They also perform a kind of simplistic EMG on your sacral roots (nerves between your spine and genitals). I was way off the mark on all these tests.

It still took me several more months to find a neurologist who took me seriously. My neurologist told me my symptoms we’re definitely abnormal and there are three places to look: 1. Your brain (MRI), 2. Your large fiber nerves (EMG), 3. Your small fiber nerves (epidermal nerve density test by biopsy).

Strangely, what actually made it all click for me, was this article ( from Dr. Healy. It all sounded suspiciously familiar, but reading through the comments it was this one that gave me chills:

“I have been doing some literature research looking for polyneuropathy and its causes, especially toxic polyneuropathy. I’m quite sure there is connection especially in regard to C-fibres. My symptoms consist, apart from the whole cascade of PSSD, from numbness of scalp, particular insensitivity to touch – I would say I can identify topographic position of the touch, basic qualities, but any emotional retine is missing – my body is not able to recognize sensual touch, caring, caressing etc. Just plain neutral touch. It is annoying. It has many consequences: I don´t feel my children cuddling with me, my partner trying to engender erotic touch and atmosphere, I don´t feel peeple if they hug me. I’m isolated, cut off my body, cut off any pleasure my body was used to convey before SSRI. I have also particular anosmia, again I can smell something but completely without any affective respond. Fine and subtreshold scent are undetectable not triggering any reaction . My erotogenic areas ceased to generate any thrill and pleasure, the same is with kissing – I used to love kising my partner – nowdays it conveys nothing – sometimes felt even disgusting – it triggers no thrill.”

I had this exact feeling and symptoms. And you may have noticed, I took finasteride, NOT SSRI’s. In fact I excluded the commenters first line: “I´m suffering from PSSD.” We’ll come back to that in a separate post.

Now armed with this symptomology I went back to my neurologist and insisted on an epidermal nerve density biopsy. The test was performed and lo and behold, I had drastically reduced densities:

Test performed by Therapath.

Epidermal Nerve Fiber Density Test

Left Thigh

Result Value: 0.4

Low Normal: 6.2 - 6.8

Right Thigh

Result Value: 0.79

Low Normal: 4.5 - 5.1

These aren’t just low, they’re almost zero! This was in January of 2019, 7 months after I first experienced symptoms. Since then (today is Aug 4, 2019) it has continued to slowly deteriorate. My entire body has barely any sensation. Touching my own body, my girlfriend’s body, having sex, even swimming or walking in a warm breeze, are all a shadow of what they used to be. I am essentially blind, but to a different sense: touch. But that’s not all, around late afternoon each day the numbness transitions into a numbness + burning sensation. Like a sunburn. Although it fluctuates, by evening of most days I am profoundly uncomfortable in my own skin (this is a hallmark of SFN.). Each night it ‘resets’ and is replaced with a sort of ‘white-out feeling’ in the morning.

It’s truly awful stuff.

Post-diagnosis I had the full battery of blood tests, including the usual suspects (diabetes, B-12 deficiency, Celiac, heavy metals, etc) as well as the rarer (autoimmune, inflammatory, etc). Everything came back negative, hence “idiopathic”.

The reason I bring this to the attention of the forum is this: I would have no direct link to finasteride to substantiate my overwhelming feeling of one, save 2 things:

  1. The timing of a decline in a number of areas: testicular size, fertility, mental health, free testosterone (more below), AND nerve health is pretty damn coincidental, but even more compelling is:
  2. There are LOT of symptoms described on this forum that match mine/those of SFN exactly and that I’m pretty confident are hidden small fiber neuropathies.

Just some examples:

Forum topics:

Poor skin sensitivity over body

Full-body rubber skin

Actually, my whole body skin feels like rubber, numbness

Numbness of the scalp

Numbness in the anal region



For the past few months I have been suffering from numbness in my rectal region. When passing stools, I had numbness in the anus and complete numbness in my anal sphincter.


very interestig. I am numb here too. also scrotum, penis and parts of my back. I will certainly try this. How long were you number for? I have recently determined that I am suffering a ‘numb’ feeling on my scalp. Its not easy to tell but it is particularly noticeable when detecting hot and cold. Since using Finasteride I also have numbness of my penis and whole genital area, even anus. I can still feel things so its not truly ‘numb’ but there is a massive loss of senstation. I wonder if anyone else that has a numb feeling in their genitals also has a numb feeling in their scalp - or am I alone?


penis feels like rubber yes, but also the whole body skin has numbness too, and feels like rubber.


Do you also have general body skin insensivity? I mean the tickle feeling when you touch yourself or from somone else, have you also experienced this skin numbness? (im not talking about penis here)


i dont know really. but its definitely a different feeling when i touch myself. it feels a bit numb and strange. numb is the wrong word but there is nearly no sensitivity and it feels awkward. i dont feel comfortable in my own body anymore. before pfs i had my erogenous zones but now they are away. i feel more/have more sensitivity when i touch my breast as when i touch the area around my penis (under stomach, penis , the erogenous zones)

Note: numb did not perfectly describe it for me either, it’s like a lack or erogenous-ness


I have the opposite side, my skin on the legs is hypersensitive, some days I can not wear my pants, but I do have to wear them and stand this shit all day long.

Note: As I mentioned above, burning hypersensitive skin is a hallmark of SFN.

I am on the other side… My skin is oversensitive, mostly on the legs, sometimes on the entire body. It feels so bad when I am dressed, the only time I feel good while I am experiencing that is when I get naked.


yes i feel like I have lost skin sensitivity over my whole body! Mainly genitals, but my whole body does not feel ticklish anymore. I just feel that I am touching it if that makes sense, there is little to no sensation in spots that used to be ticklish, nipples, thighs etc.

and I feel like my whole body has lost it feeling. I complain of numb genitals/ high, tight scrotum. I can not feel any sensation in my body, I also used to be very ticklish. Touching my inner thigh would instantly give me an erection. Feels very discconected now!


I also have a full-body rubbery skin, transparent with veins showing everywhere, insensitive to touch. When I take a shower it feels like pepper and sand, dry like Sahara desert, to the point it hurts.

Note: these strike me as someone trying to interpret a loss of feeling on their skin. It feels like you’re touching someone else!


I read some guys here who got a poor skin sensitivy. It is one of my main side effects, but few people are talking about it.I have lost approx 50% of feeling of touch in my entire body. it was as have a a slight skin anesthesia. I’d like to know why the side effect happens? What hormones are involved? or what neurotransmitter? What can I do to recover my skin sensitivtiy?


The amount of sensitivity loss varies around my body. The tips of my fingers are the worst, with about 40% loss, with all other areas being someone less. My skin also feels waxy in places, kind of like a wet suit, rather than naturally-oiled leather (i.e., healthy skin). A lot of this happened after I went off Propecia. Dermatologist have no idea what to do. What I always found odd is that, aside from my skin problems, I have no other PFS symptoms. I guess I should count myself lucky, if profoundly uncomfortable at times.

Note: this is really just dead on. “Like a wetsuit”.


I have the same thing. My finger tips are dry and dead.It has small pathches like if you burn your skin it becomes smoothe in small patches. I have very light finger prints now.


I was a very ticklish guy. As a test I had my wife try to tickle my feet and ears. This would drive me nuts before. Now I can feel the touch but no ticklish sensation… Any of you guys notice this? I think we notice right away with genital sensitivity but I swear the skin on my entire body has no pleasure receptors or whatever you would call this.


Why don’t you guys get some sensitivity testing? I had a vibration test done and it showed more than 50% lower than normal sensitivity throughout my legs, genitals, and buttocks relative to a baseline taken at my index finger.


I have bad sensitivity in many parts, but at the same time my skin gets very sensitive to clothes and hot weather, or maybe painful is the word.

Note: more burning examples, hot weather is known to make SFN worse.


Here are some of the really specific indicators that translate to small-fiber neuropathy that seem genuinely original and not easily imagined by reading from symptoms of others:

“I swear the skin on my entire body has no pleasure receptors or whatever you would call this.”

  • This is how I first noticed the loss of sensation and is consistent with a loss of fragile c-fibers which provide ‘affective touch’, whereas larger A-fibers have remained intact.

“I have lost approx 50% of feeling of touch in my entire body. it was as have a a slight skin anesthesia.”

  • I felt like someone gave me a little bit of lidocaine all over my body. It feels exactly this way, except now it’s more like 90%.

“I also have a full-body rubbery skin, transparent with veins showing everywhere, insensitive to touch.”

  • This feeling of ‘rubbery’ skin is consistent with the sensation I experienced initially. There rubberiness comes from feeling like it’s someone else’s skin. I also have experienced the thinning of skin that’s mentioned. Mostly noticeable on my penis and scrotum, where you start with thin skin and finasteride is highly active.

“When passing stools, I had numbness in the anus and complete numbness in my anal sphincter.”

  • Comments like this point to the same non-length dependent SFN because it is not local to just the penis/scrotum, where a doctor can possibly make the argument that it is related to arousal. I also experience this in general. When I wipe, the whole area is numb.


Some other symptoms and unique items in my medical history in case they catch anyone else’s eye.



  • genetic on both sides of family, on atenolol since early 20’s, switched medications around the time I started fin to losartan, have heavily researched this medication as a cause but basically zero link. Have since stopped.


  • Dealt with it my whole adult life and would relay this to doctors, led to an initial reaction from them (and to be honest, myself) that I was just ‘freaking out’.
  • I tried lexapro for 6 months in early 20’s (I’m now 34)
  • I took xanax at a low dose fairly often for 3 years, but gradually had tapered off around the time I started finasteride. I also restarted taking it to temper the panic attacks around the time I experienced numbness for the first time). This I find a little suspicious but I took it for a few months and stopped - now almost a year ago.


Loss of sensation

  • More or less even throughout body but scalp, back of neck, back/shoulders, stomach, and genitals were initially most noticeable.

Significant testicular atrophy, still continuing


Low testosterone (my total test has dropped by about 200 pts on avg over past year, pushing free test just below range)

Skin quality has degraded, aged

Very prominent veins on penis

Softer, thinner chest hair

Smell and taste significantly decreased

Depression (partially alleviated). No prior history.

Anxiety (comes and goes)

Libido (alleviated alongside depression)
Hair stopped falling out (eye roll)


OK! I will follow up this post with a separate one on the possible mechanics involved, association, null hypotheses, and the (unfortunately limited) therapeutic options.

Mainly I would love to know one thing from others, for those mentioned above and anyone else experiencing these symptoms:

  1. Have you spoken to a neurologist about small-fiber neuropathy?
  2. Most importantly, have you had a biopsy performed?

Thanks, feel free to PM me for anything specific. As the name implies, I am based in NYC, and now unfortunately I’m 34, 14 months into this mess :slight_smile:


Hi @33innyc, thanks for sharing your story. As we’ve mentioned before it’s very likely small fiber involvement is present in a lot of patients and as you may see from the expanded participation of the forum we believe pssd and pfs, as well as accutane, share a common molecular mechanism. It would be excellent if you could please take our survey which comprehensively records the symptom profile to present standardised data. This is very important to record and present the true picture of this syndrome.

Penile SFN was ruled out in multiple site biopsy of a number of pfs patients with pain and atrophy, but the scientific picture well supports the presence of sfn in some patients, so it’s always beneficial for users to share diagnostic findings.

The system will soon issue you with an invite to participate in the survey. Once this happens, you can access the survey from the bar graph icon in the top right of the forum on a desktop or laptop computer.

Thanks and best

Thanks @axolotl. Survey already submitted, let me know if you don’t see it!

I’ve searched the forum for SFN mentions and only see a few, can you point me to any rigorous mentions? I know you raised it recently with Dr. Healy’s appeal to the device maker.

I agree the results from the Di Loreto study are confounding. I don’t really have an answer other than it seems not be the case for many, the sample size was small, that there are several nerve types in play that their screens would not differentiate, and that I have heard from actual SFN pathologists that the results can really be all over the place and very hard to ascertain from all but the most experienced pathologists. Would love to see the exact patient nerve counts if you have access! Still, it’s certainly a thorn in the side of SFN being some sort of root cause and not just one of the manifestations.

Yes! Aware of the PSSD cross-pollination. In fact, I think that’s what makes SFN one of the few potential ‘concrete’ biomarkers we have - and also that could potentially unite these patient groups - and therefore a very worthy area of pursuit.

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Great post man. Thanks for posting this, very timely for me. You should check out my post right next to yours in this same category.
Main questions. So what did the neurologist recommend? Did you link this to Propecia with him?
Did he say this could come and go or be permanent?
Some of what you brought up, even from other members I know too well myself.
I will tell you right now I think this could be bacterial based, and not something you treat with antibiotics, this can make it worse as well.
If you have a open mind and it seems like you might have the means, maybe look into Viome.
It might be able to recognize bacteria and its metabolites that are overactive down to the strain.
You mention numbness around the anus, well what’s in proximity to that? The urogenital tract.
The point of this as well is to try to catch something here while its happening.
Thanks again for the post.

I experienced this too, luckily i only took 1 dose and i seem to reverse some of the damage done - I couldn’t feel my body when i crashed, i couldn’t feel showers, heat, cold, touch, taste, smell, i couldn’t feel pain, when a mosquito bit me, i’d feel it, but when i scratched myself, it felt like the itch was under my skin, i couldn’t get through…

I had a numb prostate, numb scalp, numb fingers, numb feet, numb anus, i couldn’t pee, and when i did, it’d burn through my urinary tract, i couldn’t take a shit, literally my entire system crashed.

Luckily i have had big progress since the crash, but still a lot of work before i’m pre-fin.

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I have a good neurologist from a top hospital in NYC, but she’s pretty befuddled by my case.

With small-fiber neuropathy, a good portion is idiopathic. I had to push for the inflammatory and autoimmune tests, and when I bring up essentially what I’ve explained in the post above, she’s sympathetic, but really has no idea what to do about it. She can’t make any recommendations, and is clueless about endocrinology (like all specialists outside their area).

That said, small fibers (really, peripheral fibers) can regenerate, but of course you need to address the root cause. I’m not very encouraged by this point, however, as mine continues to get worse / is not even leveling off.

If you’re interested, is a good resource.

The numbness around the anus is just part of the numbness that is everywhere so I don’t think it’s a local problem.

I hear you, though with what they know about gut bacteria these days, it seems anything is possible, but conversely it’s not a great help diagnostically.

I am curious about the markers you had tested, however. Inflammation in its various forms seems to be the root of most issues, so I would not be surprised if there’s an anti-inflammatory drug application here. Going to look into having it tested in that mayo panel (I had actually looked up that exact panel before).

Given the continuing decline, I’m pretty committed to finding some answers. FYI I will keep this thread posted as I seek fourth, fifth, sixth opinions from increasingly narrow specialists. I have at least 2 I’m scheduled to see in the next couple months.

I have to say, though, I’m surprised more people have not identified this condition, maybe they give up after being shut down by so many docs or because it requires a (very small) biopsy.


I disagree about inflation. I’ve had every inflammation test come back normal (i.e CRP)

two quick thoughts about inflammation. Chronic low grade inflammation, almost similar to an allergy, this can take its toll after some time.

inflammation can be a good thing. The body needs to know where the problem is to facilitate the healing process.

Based on alot of research, one of the most dangerous things could be when the body stops fighting what it should be fighting. When it does not generate an innate immune response. Sort of like CFS people say they never get sick, and when they do, they feel better.
There are many pathogens(or whatever a person would like to term it) where one of their “tricks” is they act as an anti-inflammatory, to fool the body to leave it alone.
Make the area “numb” to their presence.

Thanks for the post @33innyc, I will ask for this test. In which part of the body did you have the biopsy?

Extended water fast - Juicing, you want your body to cleanse itself, I’ve been juicing greens and tropical fruits/beetroots /carrots a long with drinking tons of water, as i said. My first week on my crash, i couldn’t feel my skin and suffered severely from SFN

See here:

2 very small biopsies on thigh and leg, took about 2 weeks to heal.

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I also was set to have a muscle biopsy, I backed out though. Not sure if anyone here has had this? I would assume so?

I could visit the neurologist this morning as another patient canceled his appointment. Even though I talked about the test and some of my neurological problems he saw no reason to perform any test. He checked if I perceived vibrations in my extremities and gave me a pescription for… vitamins :upside_down_face:

I have a new appointment next week with a different neurologist. I want to talk with her also about the pudendal nerve neuropathy depending on how receptive she is.

Did you see the neurologist?

I scoffed at vitamins as well, but B vitamin and other vitamin deficiencies are a common cause of SFN. Basically a malabsorption issue, or if you have a heavily vegan/vegetarian diet.

I saw a neurologist on Friday and a different neurologist today.

The one from Friday didn’t want to do any test. The one I saw today says she wants to first do an electromyogram (EMG) and neurography of the sphincter area to see if there is pudendal neuropathy.

I have the EMG scheduled for next monday.


This is an extremely important post and I congratulate @33innyc for the effort. A lot of relevant information about neuropathy in PFS is researched and clearly presented.

I personally always thought people on this site who complained they had reduced skin sensitivity on their entire body were either hypochondriacs or were grossly exaggerating something they were imagining. As I have been before with such judgments, I was wrong.

I recently realized I had had full body neuropathy all along but I had not noticed. The reduction in sensitivity is exactly as explained. It is most noticeable in very light touch because there is no tingling associated with it, something I definitely had before PFS. But it is also noticeable with more substantial touch.

The reduction in sensitivity is around 50% so enough sensitivity remains. That’s why I had not noticed it earlier. The skin on the entire body is affected, not just on the genitals.

In addition to reduced sensitivity, I also have itchiness, which I believe is a classic symptom of neuropahty. As a result, I scratch myself rather aggressively, especially on the scalp but not only, and sometimes I worry I may make a wound due to the decreased sensitivity.

This symptom should be easy to test for as there are established tests for neuropahty, as the original post talks about. I think we need to preferentially focus on it in future studies because it is something tangible that can be tested, unlike so much else in PFS.

My current theory is that perhaps this symptom is the result of low 5a-DHP and allopregnanolone, although it could be due to low levels in the brain, spine or nerves of any of the other 5a-reduced hormones.

Finally, because I only recently discovered I had this symptom, I did not include it in the survey. I suspect there are a lot of people like me who had not noticed this symptom, even though they have it.

When I shower and aim the handheld head around my penis and ass… I can’t tell the water is hot until I spray other areas than I can tell instantly it’s too hot.

I had an extreme case of neuropathy after Finasteride use in my hands and feet for months I believe in this department I was one of the most severe cases reported and I’m due to see a neurologist this month for a follow up. Nerve issues have also been reported looking at the Yellow Card Schemes adverse reactions.

I also have to perform checks at work that require touch/feeling with hands that I basically have to fake because I cannot feel a difference as to whether it’s a pass or fail. I ask numerous coworkers if they can feel a difference and they all can.

I also have had itchy scalp for years since this started. Can’t see my doctor ever going forward with tests though. At this point I figure he thinks I’m nuts.

I hate that you or anyone has had to deal with @33innyc but am thankful for your efforts and intelligence.

Ive seen enough people talk about itchiness, I sometimes think something as simple (yet of the severe type) as an allergy. Allergies can cause numbness.
Have you ever been ige tested or skin prick tested for aeroallergens?
I have seen cases of much higher doses of zyrtec being used by allergists and dermatologists then whats recommended thats otc.
Up to 40mg at least in some documented cases.
My next experiment personally.
I guess im not only thinking allergies, but switching thoughts to the h1 receptor and how it might be able to affect some autonomic functions. Sweating is a quick one that comes to mind that Ive posted on. Mediated by acetylcholine and blocked by histamine at the h1 receptor was the gist of the study.
One of my final looks at histamine.