When A Patient Presents With Thick, Yellow Toenails And A Rash On Both Feet

Michael Uro, DPM

An 80-year-old Caucasian presents to the office complaining of thick, yellow, unsightly and sometimes painful toenails. The patient, a retired RN, has had a history of a rash affecting both feet. The rash is sometimes pruritic and sometimes not. She has tried applying topical antifungals to her toenails without success. However, antifungal creams have sometimes helped her skin condition.

   The patient does not have the condition on her hands or fingernails. She has not been exposed to any harsh chemicals. She has not had trauma to her toes. She wears “good” orthopedic Oxford type shoes or open-toe shoes. The patient does complain of occasional pain of the small joints of her fingers and toes. She has not been treated for cancer.

   Upon the physical examination, I noted dystrophic, yellow, streaky, crumbly toenails. The skin of the plantar aspect of both feet was scaly with some erythema. There was no pitting of the toe or fingernails. She did display a rash on her elbows that was somewhat scaly. The patient had some swelling of the distal interphalangeal joints of the lesser toes. There were no vesicles or weeping wounds. Her vital signs were normal.

Key Questions To Consider

1. What would you include in your differential diagnosis?
2. What diagnostic tests would you perform?
3. What essential questions would you pose to this patient?
4. What is your working diagnosis?
5. How would you treat this condition?

Answering The Key Diagnostic Questions

1. Psoriasis, pityriasis rubra pilaris, traumatic onychodystrophy, bacterial infection, nail bed tumors, yellow nail syndrome, idiopathic onycholysis and paronychia congenita.
2. KOH, periodic acid Schiff (PAS) stain and fungal culture.
3. Have you had any history of a rash behind your ears, on the front of your knees or elbows?
4. The most likely diagnosis is psoriasis. However, the PAS stain was positive. She has psoriasis and onychomycosis.
5. There are several treatments for psoriasis. However, the best treatment of her psoriatic nails would be periodic debridement of the nails.

A Guide To Making The Differential Diagnosis

As I noted previously, there are a number of possible differential diagnoses for this patient.1

   Lichen planus. With this condition, it is common to see pruritic, papular eruptions with a polygonal shape and purple color. Individual lesions usually have a fine scaly surface with white striations or white puncta. Alternately, clinicians may see larger, coalesced lesions that are 4 to 5 mm in diameter. Clinicians may also see the development of lichen planus on the flexor surfaces of the upper extremities, the ankles, the anterior aspect of the lower legs, the lumbar area, the genitalia and the mucous membranes.2,3

   Pityriasis rubra pilaris. In adult acute onset type 1 pityriasis rubra pilaris, nail involvement usually presents as distal subungual hyperkeratosis with moderate thickening of the nail bed, splinter hemorrhages and longitudinal ridging.

   Traumatic onychodystrophy. This typically occurs in patients involved in high toe impact sports such as running, tennis, racquetball and similar type sports.

   Bacterial infection. Bacterial infections may cause onycholysis and mimic the onycholysis that sometimes occurs with onychomycosis.

   Nail bed tumors. Some nail bed tumors or subungual exostosis may cause dystrophy of the nail, mimicking onychomycosis.

   Yellow nail syndrome. Yellow nail syndrome is a rare disorder of the nail that usually accompanies lymphedema. It may also be associated with recurrent pleural effusions and less commonly bronchiectasis, chronic bronchitis and sinus infections. The nails are slow growing and appear to have stopped growing. The nails mainly remain smooth but there may be cross ridging and onycholysis.

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