Differential Diagnosis for Toenail and Nail Falling Out

• Single most likely diagnosis
  • Onychomycosis (fungal infection of the nail): This is the most common cause of nail falling out, especially in toenails, due to its prevalence and the fact that fungi thrive in warm, moist environments like those found in shoes.
• Other Likely diagnoses
  • Psoriasis: Nail psoriasis can cause nails to loosen and fall out due to the inflammation and thickening of the skin under the nail.
  • Trauma: Physical injury to the nail or nail bed can cause the nail to fall out.
  • Nutritional deficiencies (e.g., iron, zinc, biotin deficiency): Lack of essential nutrients can affect nail health, leading to brittleness and potential loss.
  • Aging: As people age, nail growth slows, and nails can become more brittle, increasing the risk of them falling out.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Thyroid disorders (hypo- or hyperthyroidism): Both underactive and overactive thyroid glands can cause changes in nail health, including brittleness and loss.
  • Lupus or other autoimmune diseases: These conditions can cause a variety of skin and nail symptoms, including nail loss.
  • Cancer (e.g., squamous cell carcinoma): Though rare, certain types of cancer can cause nail changes, including loss, especially if they directly involve the nail bed.
• Rare diagnoses
  • Lichen planus: An autoimmune condition that can affect the skin, mouth, and nails, leading to nail loss.
  • Alopecia areata (when it involves the nails): An autoimmune disease that primarily causes hair loss but can also affect nails, leading to brittleness, ridging, and potential loss.
  • Yellow nail syndrome: A rare condition characterized by thickened, yellowish nails that often grow very slowly and can eventually fall out.
  • Nail-patella syndrome: A genetic disorder that affects the development of nails and kneecaps, among other symptoms, and can lead to nail abnormalities and loss.