If left untreated, patients with psoriatic arthritis (PsA) are at risk of irreversible joint damage, cardiovascular disease, and death. Some other conditions conflated with PsA include chronic eczema, seborrheic dermatitis, onychomycosis, lichen planus, and nodular prurigo.
A recent case study describes a situation where a female patient was diagnosed with other conditions for about a year before specialists diagnosed her with psoriatic arthritis (PsA); the authors said they wrote the case to show how PsA can mimic other conditions.
If left untreated, patients with PsA are at risk of irreversible joint damage, cardiovascular disease, and death. Some other conditions conflated with PsA include chronic eczema, seborrheic dermatitis, onychomycosis, lichen planus, and nodular prurigo.
In this situation, the patient, age 50, had noticed some of her fingers had become deformed a year earlier, without pain; general practitioners had diagnosed her as having hand osteoarthritis. In addition, she had noticed multiple pruritic skin rashes over both ankles and knees and was also diagnosed with lichen planus; treatment with topical agents were ineffective.
By the time she saw specialists, she had severe pain, early-morning stiffness and swelling over the joints of her left ring and little fingers.
Physical examination revealed a fixed flexion deformity, swelling and tenderness of the left ring and little fingers’ distal interphalangeal (DIP) joints; a left hand radiograph showed sclerotic joint margin, narrowed joint space, and marginal osteophytes of the affected DIP joints.
A dermoscopic examination showed red-violaceous, flat-topped papules and plaques with minimal scales on both ankles; both knees and vertical fingernail ridges had hyperpigmented scaly plaques.
While serum autoimmune screening and inflammatory markers were unremarkable, a left ankle skin biopsy showed features consistent with psoriasis. Specifically, it showed “parakeratosis at the surface of the epidermis with elongation of the rete ridges; spongiosis of the epidermal layer and small capillaries proliferation seen in the papillary dermis with surrounding mixture of inflammatory cells, predominantly lymphocytes,” wrote the authors.
PsA was diagnosed. The patient began a weekly oral methotrexate 7.5 mg titrated up to 15 mg with folic acid supplement and topical betamethasone valerate cream 0.5%. She showed significant improvement after 1 month.
The authors said the case “highlights the importance of distinguishing psoriasis from other skin disorders especially lichen planus.” They also said that while both share common features, reports of both coexisting are rare.
Anne LJ, Rahim MJC, Ghazali WSW, et al. More than meets the naked eye: an unusual psoriatic arthritis mimicry and the important role of dermoscopic examination. BMC Rheumatol . Published online April 12, 2021. doi: 10.1186/s41927-021-00182-7