The diagnosis of nail deformities may not be simple. Even with nail psoriasis being one of the most common onychodystrophies, it is important to recognize other common causes, such as nail biting, self-induced or traumatic causes.1

The patient is a 48-year-old woman, smoker of 20 packs/year, with a family history of psoriasis (mother and brother). She had carpal arthritis which had lasted for 9 months, with no history of inflammatory back pain, along with major onychodystrophy of the hands and a normal skin examination (Fig. 1). Analytical studies were normal or negative, including acute phase reactants, rheumatoid factor, anti-CCP and antinuclear antibodies and HLAB27. Radiographs of hands and pelvis showed no abnormalities. Treatment was started with methotrexate and a dermatologist was consulted for suspected psoriasis with nail involvement in psoriatic arthropathy. The diagnosis was “traumatic dystrophy due to onychophagia”. The patient stopped biting her nail for 6 months (Fig. 2). The response to methotrexate has been good and she has not presented arthritis. After 4 years of follow-up, the case remains an undifferentiated arthritis, with negative CASPAR criteria for psoriatic arthropathy.

Fig. 1.

Nail disorders by onychophagia: absence of the distal end of the nail, subungual ecchymosis, callus type mechanical injury, deformity of the paronychium and characteristic grooves in the nail, indicative of chronic trauma of the nail bed.

(0.25MB).

Fig. 2.

Fingernails with no alterations after 6 months.

(0.2MB).

In all, 12% of patients with psoriasis have nail involvement, although the reported prevalence varies, being greater if there is joint involvement.2 The manifestations of nail psoriasis are multiple.3 The most common form is subungual hyperkeratosis, and nail pitting is the characteristic sign, although not pathognomonic, but oil spots under the nail bed can be considered very specific.4 It may be clinically indistinguishable from onychomycosis and differential diagnosis must also be made with other processes, including self-induced nail dystrophy (Table 1).

Onychophagia can be explained as a compulsive habit that causes the destruction of the nails. It is a common behavior among children and young adults, although underestimated, which has received little attention in the psychiatric and dermatologic literature, but can be related to obsessive-compulsive disorders.5 Complications include superinfection, paronychia and dental problems, and phalanx osteomyelitis may occur exceptionally.6 Most patients admit onychophagia, so in nail deformities it should be one of the first direct questions we ask to exclude the diagnosis.

In our patient, because of the arthropathy, it was very important to diagnose the cause of onychopathy. If the source had been psoriasis, she would have been diagnosed with psoriatic arthropathy based on the CASPAR7 criteria. However, we showed that with willpower she could stop nail-biting for 6 months. This confirms once again the importance of the history and multidisciplinary collaboration.

The authors declare no conflicts of interest.