How to Nail the Diagnosis

A 33-year-old African-American man is referred to dermatology—somewhat reluctantly—by his primary care provider for evaluation. A “fungal infection” has affected his fingernail on and off for several years, persisting despite four months of terbinafine treatment (250 mg/d).

The patient denies any antecedent trauma to the finger. He does have a history of hand eczema, mostly affecting the palmar surface of his hand, and atopy, marked by seasonal allergies and sensitive skin.

EXAMINATION
The patient’s fourth fingernail on his right hand is significantly dystrophic, with transverse ridges and modest onychorrhexis. The cuticle is detached from the nail plate, but the distal nail plate appears normal.

There are signs of his dyshidrotic hand eczema, with several 2 to 3 mm intradermal vesicles in the distal palm. Some spill onto the sides of his fingers.

What is the diagnosis?

DISCUSSION
To the unwary provider, every fingernail problem is fungal in nature; they simply have no other items in their differential, which is why terbinafine is overprescribed for nonfungal conditions. Even when we suspect fungal infection, the appropriate course would be to sample the nail plate and send it for culture or pathologic examination—not just throw another prescription at it.

However, in cases such as this one, there are other explanations. This patient’s nail issues are secondary to his eczema and are likely related to the disconnect between the cuticle and the nail plate. This gap allows debris (bits of food, dirt, etc) access to the nail matrix, thereby causing a misshapen nail. The key to diagnosis is the transverse ridging and detached cuticles. A history of hand eczema bolsters this impression—infection is not involved.

Application of a mid-strength steroid ointment to the cuticle area encourages it to reattach to the nail. This gives the nail a chance to grow in normally.

TAKE-HOME LEARNING POINTS
• Fungal infections are significantly (18 times) more common on toenails than on fingernails.
• Eczema on the hand or body can also lead to transverse ridges in fingernails, especially when the cuticle detaches from the nail plate.
• Other items in the differential include psoriasis, lichen planus, and nail changes associated with alopecia areata.

A 33-year-old African-American man is referred to dermatology—somewhat reluctantly—by his primary care provider for evaluation. A “fungal infection” has affected his fingernail on and off for several years, persisting despite four months of terbinafine treatment (250 mg/d).

The patient denies any antecedent trauma to the finger. He does have a history of hand eczema, mostly affecting the palmar surface of his hand, and atopy, marked by seasonal allergies and sensitive skin.

EXAMINATION
The patient’s fourth fingernail on his right hand is significantly dystrophic, with transverse ridges and modest onychorrhexis. The cuticle is detached from the nail plate, but the distal nail plate appears normal.

There are signs of his dyshidrotic hand eczema, with several 2 to 3 mm intradermal vesicles in the distal palm. Some spill onto the sides of his fingers.

What is the diagnosis?

DISCUSSION
To the unwary provider, every fingernail problem is fungal in nature; they simply have no other items in their differential, which is why terbinafine is overprescribed for nonfungal conditions. Even when we suspect fungal infection, the appropriate course would be to sample the nail plate and send it for culture or pathologic examination—not just throw another prescription at it.

However, in cases such as this one, there are other explanations. This patient’s nail issues are secondary to his eczema and are likely related to the disconnect between the cuticle and the nail plate. This gap allows debris (bits of food, dirt, etc) access to the nail matrix, thereby causing a misshapen nail. The key to diagnosis is the transverse ridging and detached cuticles. A history of hand eczema bolsters this impression—infection is not involved.

Application of a mid-strength steroid ointment to the cuticle area encourages it to reattach to the nail. This gives the nail a chance to grow in normally.

TAKE-HOME LEARNING POINTS
• Fungal infections are significantly (18 times) more common on toenails than on fingernails.
• Eczema on the hand or body can also lead to transverse ridges in fingernails, especially when the cuticle detaches from the nail plate.
• Other items in the differential include psoriasis, lichen planus, and nail changes associated with alopecia areata.

A 33-year-old African-American man is referred to dermatology—somewhat reluctantly—by his primary care provider for evaluation. A “fungal infection” has affected his fingernail on and off for several years, persisting despite four months of terbinafine treatment (250 mg/d).

The patient denies any antecedent trauma to the finger. He does have a history of hand eczema, mostly affecting the palmar surface of his hand, and atopy, marked by seasonal allergies and sensitive skin.

EXAMINATION
The patient’s fourth fingernail on his right hand is significantly dystrophic, with transverse ridges and modest onychorrhexis. The cuticle is detached from the nail plate, but the distal nail plate appears normal.

There are signs of his dyshidrotic hand eczema, with several 2 to 3 mm intradermal vesicles in the distal palm. Some spill onto the sides of his fingers.

What is the diagnosis?

DISCUSSION
To the unwary provider, every fingernail problem is fungal in nature; they simply have no other items in their differential, which is why terbinafine is overprescribed for nonfungal conditions. Even when we suspect fungal infection, the appropriate course would be to sample the nail plate and send it for culture or pathologic examination—not just throw another prescription at it.

However, in cases such as this one, there are other explanations. This patient’s nail issues are secondary to his eczema and are likely related to the disconnect between the cuticle and the nail plate. This gap allows debris (bits of food, dirt, etc) access to the nail matrix, thereby causing a misshapen nail. The key to diagnosis is the transverse ridging and detached cuticles. A history of hand eczema bolsters this impression—infection is not involved.

Application of a mid-strength steroid ointment to the cuticle area encourages it to reattach to the nail. This gives the nail a chance to grow in normally.

TAKE-HOME LEARNING POINTS
• Fungal infections are significantly (18 times) more common on toenails than on fingernails.
• Eczema on the hand or body can also lead to transverse ridges in fingernails, especially when the cuticle detaches from the nail plate.
• Other items in the differential include psoriasis, lichen planus, and nail changes associated with alopecia areata.