What Causes Green, Blue, Black, Yellow Fingernails?

Green, blue, black, yellow fingernails can have various causes, ranging in severity from 'minor' to 'generally fatal'. Finding the true cause means ruling out or confirming each possibility – in other words, diagnosis.

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Diagnosis is usually a complex process due to the sheer number of possible causes and related symptoms. In order to diagnose green, blue, black, yellow fingernails, we could:

Research the topic
Find a doctor with the time
Use a diagnostic computer system.

The process is the same, whichever method is used.

Step 1: List all Possible Causes

We begin by identifying the disease conditions which have "green, blue, black, yellow fingernails" as a symptom. Here are eight of many possibilities (more below):

Pulmonary Embolism
HIV/AIDS
Drug Side-Effects
Lung Cancer
Wilson's Disease
Diabetes II
Hypothyroidism
Psoriasis

Step 2: Build a Symptom Checklist

We then identify all possible symptoms and risk factors of each possible cause, and check the ones that apply:

occasional itchy eyes

somewhat elevated basophil count

low energy/stamina

constant thirst

grooves across fingernails

frequent swollen inguinal nodes

late term miscarriage

multiple swollen cervical nodes

minor joint pain/swelling/stiffness

cracked skin

pitted nails

multiple painful cervical nodes

... and more than 110 others

Step 3: Rule Out or Confirm each Possible Cause

A differential diagnosis of your symptoms and risk factors finds the likely cause of green, blue, black, yellow fingernails:

Cause	Probability	Status
HIV/AIDS	94%	Confirm
Psoriasis	24%	Unlikely
Drug Side-Effects	22%	Unlikely
Wilson's Disease	1%	Ruled out
Lung Cancer	1%	Ruled out
Diabetes II	0%	Ruled out
Pulmonary Embolism	0%	Ruled out
Hypothyroidism	0%	Ruled out

* This is a simple example to illustrate the process

Arriving at a Correct Diagnosis

The Analyst™ is our online diagnosis tool that learns all about you through a straightforward process of multi-level questioning, providing diagnosis at the end.

If you indicate abnormal fingernails and toenails, The Analyst™ will ask further questions including this one:

Are (parts of) your fingernails any unusual color other than white?

Possible responses:

→ No / another color (add a note) / don't know
→ Green / greenish
→ Blue / bluish
→ Black / somewhat brown
→ Yellow / yellowish

Based on your response to this question, which may indicate green/greenish fingernails, blue/bluish fingernails, black/brown fingernails or yellow/yellowish fingernails, The Analyst™ will consider possibilities such as:

(Prescription) Drug Side-Effects

Black nails (melanonychia) can be a medication side-effect, particularly of cyclophosphamide (Cytoxan).

Asthma

Chemotherapy Side-Effects

Black line(s) across the nails are common in dark-skinned persons but may also be the result of injury or chemotherapy.

Congestive Heart Failure

COPD (Chronic Obstructive Pulmonary Disease)

Diabetes Type II

Emphysema

Fungal Skin / Nail Infection

Green nails are generally due to a Pseudomonas pyocyanea infection. One of the most common causes of yellow nails is a fungal infection. Black nails are a possible indication of bacterial or fungal infection.

HIV/AIDS

Black nails are sometimes seen in people infected with AIDS.

Hypothyroidism

Lung Cancer

Melanoma

A longitudinal brown-black streak (which may take up the whole nail and may "spill over" into the proximal nail fold) is a sign of melanoma, and possibly Hutchinson's.

Ochronosis / Alkaptonuria

Pneumonia

Nails with a bluish tint can mean the body isn't getting enough oxygen. This could indicate an infection in the lungs, such as pneumonia.

Psoriasis

Pulmonary Embolism

Raynaud's Phenomenon

Wilson's Disease

Concerned or curious about your health? Try The Analyst™