From the Guidelines
Spoon-shaped nails (koilonychia) are most commonly associated with iron deficiency anemia, which is the primary condition to consider when this nail abnormality is observed. However, several other medical conditions can also cause koilonychia, including:
- Hemochromatosis (ironically, an iron overload disorder)
- Raynaud's disease
- Lupus erythematosus
- Thyroid disorders, particularly hypothyroidism
- Occupational trauma from repeated exposure to petroleum-based solvents or trauma
- Certain infections like syphilis
- Nutritional deficiencies beyond iron, such as vitamin B12, folate, or protein malnutrition
In infants, koilonychia can be physiologically normal and typically resolves with age. The characteristic spoon shape occurs because the nail matrix produces a thinner nail plate that cannot maintain its normal convex shape, causing it to become concave and sometimes brittle. When koilonychia is identified, a complete blood count and iron studies are typically recommended as initial diagnostic steps to identify the underlying cause, which then guides appropriate treatment 1.
From the Research
Medical Conditions Associated with Spoon-Shaped Nails
The medical conditions associated with spoon-shaped nails, also known as koilonychia, include:
- Iron deficiency anemia 2, 3, 4
- Hemochromatosis 2
- Psoriasis 4, 5
- Lichen planus 4
- Onychomycosis 4
- Plummer-Vinson Syndrome 4
- Nutritional deficiencies 4
- Occupational or traumatic causes 4
- Alopecia areata 6
- Connective tissue disorders 2
- Hyperthyroidism (in the absence of trauma or psoriasis) 2
- Inflammatory bowel disease (associated with clubbing of the nails) 2
- Pulmonary disease (associated with clubbing of the nails) 2
- Raynaud's disease (associated with Beau's lines) 2
- Endocarditis (associated with splinter hemorrhage) 2
Systemic Disease Associations
Koilonychia may be a manifestation of an underlying systemic disease, and its presence should prompt investigations for iron deficiency 3 and other potential causes. A thorough but reasonable search for a primary etiology should be made when a patient presents with spoon nails or clubbing 5.
Idiopathic Cases
It is worth noting that some cases of koilonychia are idiopathic and of no consequence to the patient 3, 5. In these cases, reassurance and monitoring may be sufficient.