It’s odd how we seem to find ourselves with very niche interest areas in Emergency Medicine. Paronychia is one of mine, for a variety of reasons – probably firstly because I used to be a nail-biter and so had a lot of paronychia growing up, secondly because I had some great teaching from some Nurse Practitioners on the topic early in my ED career and thirdly because I made a Borat-themed Paronychia quiz for registrar teaching when I was a trainee that I remain unjustifiably proud of.
What is – and What isn’t – a Paronychia?
Let’s start with some anatomy (hurrah!)
Paronychia is an infection of the skin at the nail fold (the paronychium). Other terms are often used interchangeably but incorrectly: a felon is a pulp infection (abscess) occurring on the palmar (non-nail) side of the phalanx; a whitlow is usually an herpetic infection of the soft tissues of the distal phalanx (more on that later too).
If you’re interested in the morning after pill, you need to know that is a type of emergency birth control (contraception). Emergency contraception is used to prevent pregnancy in women who’ve had unprotected sex or whose birth control method has failed.
Surely that’s not an Emergency Department problem?!
You might be right. All of my childhood paronychia were managed by my (non-medical) Mum, using hot water and encouragement to stop biting my nails (more on that later). But these patients do come to the Emergency Department, or minor injuries unit, so we should probably have some idea what to do with them.
What’s more, patients can die from paronychia.
Probably not healthy patients, but this open access case report describes disseminated Fusarium infection in a patient with neutropenia from AML, thought to have arisen from a toenail paronychia.
An acute paronychia, like the one above, is typically of relatively short onset and evolves over a few days. It can occur in fingers or toes, on the radial or ulnar (medial or lateral in toes) side of the nail. The usual infective organism is Staph. aureus in adults (mouth flora in children); the affected digit is red, warm, painful and swollen, sometimes with reported or visualised pus (you can sometimes see a little dried crusty yellow collection at the nail fold). The infection commonly follows minor nail trauma, such as a manicure or, more commonly, nail biting or sucking.
There is sometimes a small collection of pus between the nail and the paronychium, unable to escape due to the superficial adhesion of the skin to the nail. Untreated for a period of time, the paronychia may evolve into associated cellulitis with or without ascending lymphangitis, or chronic paronychia.
Management of acute paronychia is a surprisingly evidence-light area. Firstly, for a simple acute paronychia, there is no evidence that antibiotic treatment is better than incision and drainage. If there is associated cellulitis of the affected digit (or, Heaven forbid, systemic infection) or underlying immunosuppression, then antibiotic therapy should be considered, but your first priority ought to be to get the pus out.
There are a couple of ways to do this. The simplest, least invasive way (and the one I teach my patients!) is to soak the affected digit in warm water and then, once the skin has softened, to gently separate the skin of the lateral nail fold from the nail itself using a sterile flat, blunt-edged instrument. This technique is pretty old; in fact, while looking for images to use in this post I came across this picture from “The Practice of Surgery (1910)”
According to Flickr, where I found this image, text before the picture reads:
Here is a better way. Lay a narrow-bladed knife flat upon the nail with the knife against the inflamed skin, and by a little gentle prying, which should be painless, insert it along the skin-edge and the base of the abscess. Withdraw the point, when we see it followed by a jet of pus. By a little manipulation the cavity is now evacuated; a poultice is then applied. Unless the nail and matrix have become involved in the infection, sound healing should now be a matter of two or three days only.
This video from YouTube shows a similar technique; honestly you will get the same result if you use something flat but relatively blunt (Arthur/splinter forceps work brilliantly) having first soaked the finger for 10mins+. You can use an 18G needle or (gently!) use a scalpel if you can’t find anything slim and blunt-edged but the idea is not to cut or pierce the skin. Focus on separation of the tissues, as seen below.
In this alternative, Larry Mellick uses a scalpel blade after digital block for a more extensive collection; you get the impression that the blade isn’t being used to cut as much as separate the tissues (although here he is inserting into the eponychium as you now know :-))
Once the pus is out, the pain will improve quite a bit (although not altogether to begin with). Because you aren’t cutting the skin (in my approach), ring block or local anaesthesia is usually unnecessary. You are simply “opening the eponychial cul-de-sac” to allow the pus to escape. You can consider inserting a wick (1cm of 1/4″ gauze) afterwards if you really want to, in order to facilitate ongoing drainage. As you express the last of the pus, you will sometimes get some blood mixed with it which is normal and to be expected considering the vascularity of the finger and the degree inflammation present before you start.
At this point I usually advise the patient to follow the same technique four times/day and, with careful safety netting (particularly advice that it should improve within 24h and to return if the erythema spreads or they feel unwell; I also warn them that if the pus recollects we might need to excise a portion of the nail), I let them go home without antibiotics. A review is pretty sensible although this can usually occur in the community rather than ED. This is an approach I have adopted from my ENP colleagues – and definitely a study I need to do, given the paucity of published evidence therein (if you fancy being a co-author, get in touch and let’s make it happen!).
Some practitioners use topical antibiotics for these patients and there is some evidence that if you are going to give topical antibiotics, there is some (weak) evidence that adding a topical steroid (betamethasone) to your fusidic acid might speed up resolution of pain. I do tend to send a pus swab off if I get some good stuff out – particularly for those immunocompromised patients I’m going to treat with antibiotics from the outset.
The other common management strategy is to excise a portion of the nail to allow pus drainage. If you are going to be cutting things, do perform a ring or digital block first and allow time for the local anaesthetic to work. Remember from your vast pharmacology knowledge that most local anaesthetics as weak bases and are unable to cross lipid membranes in acidic conditions – so local infiltration of infected tissues does not work (read more here).
Then perform the same steps as above or make a small incision into the swollen skin overlying the collection of pus, with or without the addition of excision of 3-5mm of the width of the nail (note – I have never done this in clinical practice as separating the nail from the skin seems to work effectively to release pus for the patients I have seen. If you genuinely think excision of the nail might be required, this would probably be better dealt with by a hand surgeon). If you are incising you might consider putting in a wick: a thin piece of sterile gauze will suffice although the jury is out on whether this is a useful intervention in itself (I’ll be looking out for the results of this study on wick vs packing for abscess care).
Of course, we sometimes see patients at a second presentation, after simple therapies have failed. It is probably worth considering both antibiotic therapy for those patients – although we can discuss with them the risks and benefits of antibiotic therapy in an evidence-light area. I only really consider oral antibiotics in the presence of associated cellulitis or in immunosuppressed patients as simple paronychia will improve as soon as the pus is released. Antibiotics with Staphylococcal cover, such as flucloxacillin, are a reasonable first line therapy although it might be worth sending some of that pus off for culture if you can and instead prescribing co-amoxiclav or clindamycin as MRSA does occur and anaerobes may be responsible in nail-biters and finger- or thumb-suckers. Just to reiterate, sending a pus swab off if you’re treating with antibiotics (and perhaps even if you aren’t) might help you further down the line.
If what you’re seeing is particularly crusty, consider whether there might be a herpetic infection instead of bacterial. Herpetic whitlow is common secondary to Herpes simplex (exogenous or autogenous) and may be seen in children, teenagers, sex workers, healthcare workers and historically in dentists (though I suspect most area invested in wearing gloves nowadays, reducing their exposure) – basically anyone who has exposure to perioral Herpes simplex at their fingertips (toes are a bit less common… for most people). You might see multiple vesicles and visible signs may be preceded by reported symptoms of itching, burning or tingling in the affected digit. Early oral aciclovir is the usual suggested therapy.
Chronic (Fungal) Paronychia
Chronic paronychia is a little different. It is a kind of dermatitis-type reaction, usually representing damage to the protective barrier of the nail or its tissues, often due to frequent hand washing and/or exposure to harsh chemicals or cold and wet (for this reason, chronic paronychia are more often seen in people who handwash a lot – such as healthcare workers, bar tenders and food processors – and in swimmers, fishermen etc.). Often more than one finger is affected; nail changes such as pitting may be seen too.
In addition, immunosuppressed patients are more likely to have chronic paronychia, particularly diabetics and those on steroids. It is worth noting that indinavir (an antiretroviral drug) is associated with chronic paronychia, particularly of the big toe, which resolves when the drug is ceased. Psoriasis might also predispose to chronic paronychia as well as being a differential diagnosis in these patients.
Candida albicans and/or Pseudomonas may be cultured. Treating the underlying dermatitis is very important: avoidance of further irritants together with emollient use is a good start. Topical steroids are first-line therapy but culture is really important here: steroids are usually given with topical antifungal but oral antifungal such as itraconazole or fluconazole may be indicated if C.albicans is isolated.
Other Mimics and (Weird) Differentials
A favourite among SAQ-writers, flexor tenosynovitis is an acute (bacterial) infection within the finger’s flexor sheath which may arise following penetrating trauma to the tendon sheath or as spread from an untreated felon. There are four cardinal signs as described by Kanavel:
- Fusiform swelling of the digit (the whole finger is swollen, rather than localised swelling in local infection)
- The finger is held in flexion
- Intense pain is experiences on attempts to extend the finger along the course of the tendon
- There is percussion tenderness along the course of the tendon sheath
These patients should be referred to hand surgeons for surgical drainage and treated with antibiotics covering Staph. aureus in the first instance.
Less common nowadays, prosector’s paronychia was so-called because it was seen in anatomists and dissectors – people with lots of hand-in-corpse time. It might present as a chronic, painless paronychia more visually in-keeping with the acute type and/or refractory to acute paronychia treatment. The giveaway is usually axillary lymphadenopathy, biopsy of which grows Mycobacterium tuberculosis. As such, this is a systemic manifestation of TB infection and should be treated with systemic TB meds
This difficult-to-pronounce condition looks like psoriasis, affecting all digits with nail changes, and is associated with carcinoma of upper respiratory and GI tracts particularly SCC of the larynx. Patients may have scaly eruptions on the ears, cheeks and nose and will usually have other systemic symptoms too; the condition may resolve completely with treatment of the underlying cancer and recurrence may be indicated if symptoms and signs return. There’s a nice summary over at Dermnet.NZ.