Differential Diagnosis of Nail Dystrophy

The differential diagnosis for nail dystrophy is broad and can be categorized based on the likelihood and potential impact of missing a diagnosis. Here's a structured approach:

• Single Most Likely Diagnosis
  • Onychomycosis: This is a fungal infection of the nails and is the most common cause of nail dystrophy. It presents with thickening, discoloration, and brittleness of the nails. The high prevalence of onychomycosis in the population makes it the single most likely diagnosis for nail dystrophy.
• Other Likely Diagnoses
  • Psoriasis: Nail changes are common in psoriasis, including pitting, onycholysis (separation of the nail from the nail bed), and subungual hyperkeratosis (debris under the nail). The presence of skin psoriasis increases the likelihood of these nail changes.
  • Eczema/Dermatitis: Eczema or dermatitis around the nails can lead to nail dystrophy. This includes conditions like atopic dermatitis or contact dermatitis, which can cause nail changes due to inflammation and irritation.
  • Trauma: Repeated or significant trauma to the nails can cause dystrophy. This includes physical injury, excessive exposure to chemicals, or habitual behaviors like nail biting or picking.
• Do Not Miss Diagnoses
  • Squamous Cell Carcinoma: Although rare, squamous cell carcinoma can present as nail dystrophy, especially if it involves the nail bed. Missing this diagnosis could have severe consequences, including local destruction and potential metastasis.
  • Melanoma: Subungual melanoma is a type of skin cancer that can present under the nail, causing dystrophy. It is crucial to consider this diagnosis, especially in cases of unilateral nail changes or pigmentation under the nail.
• Rare Diagnoses
  • Lichen Planus: This is an autoimmune condition that can affect the nails, leading to dystrophy. It is less common than other causes but should be considered, especially if there are other systemic or mucocutaneous manifestations.
  • Darier's Disease: A rare genetic disorder that affects the skin and sometimes the nails, leading to dystrophy among other symptoms.
  • Yellow Nail Syndrome: A rare condition characterized by slow-growing, thickened, yellowish nails, often associated with lymphedema and respiratory diseases.

Each of these diagnoses has distinct features and implications for patient care. A thorough history, physical examination, and sometimes additional diagnostic tests (like nail clippings for fungal culture or biopsy for suspected malignancies) are necessary to determine the underlying cause of nail dystrophy.