The clinical relevance of nail signs

Clubbing

Thus far, the college's interest in your nails has been limited to clubbing. Specifically,  Question 24.1 from the first paper of 2009 asked the candidates for a few causes of clubbing which were not cardiac or respiratory. Everybody always goes crazy over clubbing. , and goes to grab the medical students. All gather around the clubbed patient, hooting excitedly. Is clubbing really that important?

Probably not. Usually, if your patient has developed clubbing, they have also likely developed some other major organ system problem which has become apparent and has brought them to your ICU.

However, there are still those few occasions where isolated clubbing might suddenly point one in the direction of a lung tumour which nobody noticed on the chest Xray, while the patient is admitted for something completely different. Such a finding may change the direction of care.

The aetiology of clubbing is poorly understood, and the various authors tend to refer to megakaryocytes or platelet clumps which are not filtered by the lung for whatever reason. This of course is an unsatisfying and incomplete explanation. But we don't have a better one.

In short, causes of all-digit clubbing can be divided into a few groups:

• Malignancy of some sort, somewhere
• Chronic respiratory disease of some sort
• Chronic heart failure of some sort
• Chronic infectious or inflammatory conditions like empyema or ulcerative colitis
• Cirrhosis
• Weird stuff like syringomyelia and hyperparathyroidism

As Ganesh, an attentive reader, has pointed out, clubbing should not be attributed to COPD.

However, it is associated so frequently with COPD that even respectable journals publish articles attributing clubbing to COPD, which prompts angry letters to the editor. COPD and clubbing are only associated insomuch as COPD and lung cancer are associated. The author of "Dear Editor," suggests that "clubbing in the context of COPD should prompt further investigation into respiratory causes of clubbing, such as bronchogenic carcinoma, interstitial pulmonary fibrosis or chronic lung infections including bronchiectasis, lung abscess or empyema".

Leukonychia

Basically, your nails should be pink. White nails are a signal of some sort of badness.

Leuconychia can be associated with numerous things. Early medical authors suggested it may be a sign of impending death, which was probably frequently accurate. An excellent overview can be found in a recent article by Tuzun and Karakus.

In general, leukonychia is associated with the following pahologies:

• Minor nailbed trauma (leuconychia of a single nail)
• Hypoalbuminaemia and liver disease
• Lymphoma
• Chemotherapy
• Fungal infection (onychomycosis)
• Calcium or zinc deficiency
• Congenital leukonychia
• CCF
• Heavy metal poisoning
• Leprosy
• Pellagra

There are also some eponymous forms of this sign.

Eponymous nail signs:

 

Lindsay's Nail

"Half-and-half" nails, where the whole proximal half is pale, and the whole distal half is brown or pinkish. The lunule is lost. Resus.com.au have a nice image of this.

There really seems to be only one clinical association:

• Chronic renal failure

Terry's Nail

A brownish discolouration of the distal nail bed, with the rest of the nail remaining pale. The normal lunule tends to be totally absent. Wikipedia kindly favours us with some images of this sign. The pathophysiology seems to be some sort of distal subungual telangiectasia. The causes of this sign are as follows:

• Cirrhosis
• CCF
• NIDDM
• Just straight-out old age.

Eponymous nail lines:

Muehrcke's lines

This is known as "leukonychia striata". Basically, there are line parallel to the lunula, radiating across the nail. Wikipedia has a nice picture. Weirdly these are actually vascular structures under the nail itself, and they do not move with nail growth. One can distinguish these from other sorts of parallel nail lines by putting pressure on the nail - Muehrcke's lines will blanch, where others will not.

These lines are typically see in patients with low albumin, for whatever reason.

Its a pretty non-specific finding.

• Poor protein synthesis in general
• liver disease
• malnutrition
• nephrotic syndrome

Mee's lines

Confusingly, Mee's lines are also sometimes called "leukonychia striata". Unlike Muehrcke's lines these are in the nail itself. The lines are pale and parallel to the lunula, but they do not blanch on pressure, and they move with the nail as it grows.

Again, I defer to Wikipedia for images, because I cant be bothered to hunt down consent and photograph any actual patients.

These lines are somewhat more specific. The are associated with:

• Arsenic poisoning
• Thallium poisoning
• Generally speaking, any heavy metal poisoning
• Chemotherapy (which one can view as a refined form of poisoning)

Beau's lines

Again, these are lines which run parallel to the lunula, but they are not pigmented- rather the line is a deep groove in the nail itself. It represents a period of slowed or aborted nail growth, which is what one tends to expect in periods of serious critical illness, or with administration of drugs which interfere with the cell cycle. Each admission to ICU with severe sepsis would probably result in just such a line. Alternatively, only one limb might be affected, and the lines might form as a result of major limb trauma.

Thus, the clinical associations of Beau's lines are as follows:

• Severe illness
• Starvation
• Limb trauma (or even nail trauma)
• chemotherapy

Onycholysis

The degradation of a nail could be for a number of reasons, of which local reasons are dominant - it might be that the nail bed has suffered some sort of trauma, and the nail is falling apart because of this. However, systemic disease would cause a breakdown of all the nails, and this is more concerning.

The conditions associated with onycholysis are as follows:

• Psoriasis
• Traumatic nailbed damage
• Fungal infection
• Hyperthyroidism
• Vascular insufficiency, including atherosclerotic disease, vasculitis or Raynauds.

Koilonychia

Dermnet.com has a nice picture of a "spoon nail". Apparently the appearance of the nail has something to do with lower cysteine content of the nail.

Koilonychia is classically associated with the following conditions:

• Chronic iron deficiency
• Chronic organic solvent exposure of the hands ("Hairdressers nails")
• High altitude

Splinter haemorrhages

The consequence of microembolic events or vasculitis, splinter haemorrhages are tiny little red-brown streaks which appear parallel to the long axis of the nail. Dermnet has a good picture of some splinter haemorrhages.

These can be associated with a variety of conditions:

• Infective endocarditis
• Vasculitis of any sort

Nicotine stains

I will not insult the intelligence of the readers by discussing at lengths the pathophysiological correlations of nicotine stains. I will instead practice misdirection by referring them to an angry letter of retort by a smoker, who reminds his readers that it is unscientific to refer to the stained hands as "nicotine" stains and that any products of combustion will ultimately produce this.

Vertical nail ridges

The ridges which run longitudinally along a nail suggest some sort of nutritional deficiency. Conventional wisdom attributes these to iron deficiency and states of "chronic disease anaemia", such as various forms of chronic inflammatory arthritis.

Horisontal nail ridges

Horisontal ridging - or rather, band-like changes in the quality of the nail - are most commonly associated with periods of decreased protein anabolism. Dull lacklustre nail material is formed during periods of extreme stress, critical illness, malnutrition, chemotherapy, and other similar destructive processes. Alternating episodes of normal health and critical illness may be recorded chronologically in the form of horisontal nail ridges.