Spoon Nails (Koilonychia)

Spoon nails, medically known as koilonychia, are indented nails that appear scooped in like a spoon. Rather than growing straight, the nails curve inward. A common cause of spoon nails is iron deficiency anemia. Other possible causes include inflammatory skin conditions and genetic disorders. 

Besides appearing curved-in, spoon nails might also be thin, weak, and brittle. Spoon nails can impact your fingernails, toenails, or both. The curved nails usually develop slowly over time. In rare cases, a newborn may be born with koilonychia. 

Treatment for spoon nails depends on the underlying cause and may include iron supplements.

Spoon Nail Symptoms 

Spoon nails get their name because the nails are shaped like a spoon. The curved indentation may be vertical or horizontal on the nail. The indent will develop gradually, as the nail grows.

In addition to appearing scooped-in, the nails may feel brittle, weak, and thin.

Because spoon nails are often a sign of an underlying health condition or nutritional deficiency, you might also experience symptoms related to the condition or deficiency.

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What Causes Spoon Nails? 

Spoon nails occur when the nails grow into a curved shape instead of straight.

The most common cause of spoon nails is iron deficiency anemia, when there's too little iron to make enough red blood cells. About 5% of people with iron deficiency anemia experience spoon nails.

Researchers believe having low iron levels could result in poor blood flow to the fingers and toes. This may weaken the connective tissue (tissue that connects and supports your body) under your nail bed, leading to spoon nails.

Iron deficiency is just one systemic condition that can cause spoon nails. A systemic condition is a health condition that affects the entire body. Other systemic conditions that may cause spoon nails include:

• Nutritional deficiencies: Besides iron, a deficiency of vitamin C, zinc, copper, selenium, cysteine, and other amino acids can cause spoon nails.
• Plummer-Vinson syndrome (PVS): This is a rare condition that causes iron deficiency anemia along with difficulty swallowing (dysphagia) because of web-like tissue in the esophagus. About 37%-50% of people with PVS experience spoon nails.  
• Hemochromatosis: This genetic disorder affects iron accumulation and causes spoon nails in 49% of cases. 
• Endocrine disorders: People with underactive thyroid (hypothyroidism) may have spoon nails, slowed nail growth, and brittle nails. Diabetes may cause spoon nails because of nutrient deficiencies or blood vessel damage.
• Autoimmune or autoimmune-associated conditions: Spoon nails are rare in people with systemic lupus erythematosus and Raynaud’s disease, but they are possible.  
• Occupational spoon nails: When a person is exposed to mineral oil (petroleum), organic solvents, or chemicals that cause skin irritation, contact dermatitis, or repeated trauma (injury), they may develop spoon nails. 

Skin conditions are another main cause of spoon nails. Skin conditions that may cause spoon nails include:

• Lichen planus: This inflammatory skin condition causes the immune system to attack cells in the nails, skin, and mouth.
• Nail psoriasis: Psoriasis is an autoimmune condition that occurs when the skin cells multiply too quickly. Sometimes psoriasis can affect the nails
• Trachyonychia (20-nail dystrophy): This chronic condition of the nail causes rough, opaque nails.
• Onychomycosis: This is a fungal infection of the nail bed.

People of all ages can experience spoon nails. Some people are even born with the indents. In 33% of newborn cases, the condition will resolve on its own. Children who suck their thumb or fingers may develop spoon nails. Rarely, spoon nails can run in families. 

Diagnosis

To determine whether you have spoon nails, a healthcare provider will likely start by performing a physical exam and reviewing your medical history. They will probably ask questions about your health history, family history, eating habits, and lifestyle factors.

They may perform a diagnostic test known as a water drop test. For this, they will drop water over the nail plate and see if the droplets pool in the nail.

They may also order bloodwork, including a complete blood count to test for anemia or an iron panel to determine if iron supplements are needed. 

Treatments for Spoon Nails  

There is nothing harmful about spoon nails themselves. However, the underlying cause of the nails may need to be treated.

The goal of treatment is to address the underlying cause and, in doing so, have your nails grow straight out. If you do not treat the underlying condition, your nails can become more spooned. Once the health condition causing spoon nails is treated, the nails usually start growing normally.

The treatment plan depends on the underlying cause.

Many cases of spoon nails are related to an iron deficiency. If this is the cause for you, your healthcare provider will likely recommend incorporating iron-rich foods like beans, leafy greens, and fortified grains into your diet. You may also need an iron supplement.

Research shows that once a person receives treatment for anemia, their spoon nails usually heal within four to six months of starting an iron supplement.

Spoon nails affecting the toenails can take as much as a year and a half to go away since toenails take longer to grow. 

Prevention

Spoon nails are usually a symptom of another health condition. If you already have the underlying condition, there might not be anything you can do to prevent spoon nails from developing. Properly managing the underlying condition may be able to help prevent spoon nails.

You can also try to prevent spoon nails by keeping your nails short and clean. Using a moisturizer or oil on your nails after you shower can also help. 

Related Conditions 

The most common cause of spoon nails is iron deficiency anemia. Over time, iron deficiency anemia can lead to several health conditions, including:

• Heart conditions: A severe iron deficiency puts stress on the heart and may lead to fatigue, breathing trouble, and heart disease. 
• Infections: A lack of iron affects the immune system’s ability to fight infection.
• Developmental delays: Pregnant people with iron deficiencies are at increased risk for having children with developmental delays. 
• Pregnancy complications: Pregnant people with iron deficiencies are more likely to have a premature birth or a baby with a low birth weight. 
• Depression: Iron affects the balance of brain chemicals, and a deficiency may lead to mood changes. 
  

A Quick Review

Spoon nails (koilonychia) is a condition that occurs when the fingernails or toenails grow into a curved shape. Spoon nails appear scooped like a spoon—the middle part of the nail is lower than the outer edges. Spoon nails also feel weak, brittle, and thin. The most common cause of spoon nails is iron deficiency anemia. Other possible causes include inflammatory skin conditions, malnutrition, and autoimmune conditions. 

Spoon nails themselves are not harmful, but the underlying condition may need to be treated. The goal of treatment is to manage the underlying condition, which will likely return nails to their normal shape as they grow out. Many people with spoon nails require a daily iron supplement.