Painful 20 fingers' onychodistrophy.

Psoriatic onycho-pachydermo-periostitis (POPP) is a rare subset of psoriatic arthritis. It is usually localized to the hands and it is characterized by onychodistrophy, soft tissue thickening above the distal phalanx and periosteal reaction. The resolution is very slow due to the involvement of nails and bone. Low dose methotrexate and anti-tumor necrosis factor-α (anti-TNF-α) agents are the suggested therapies. We report a case of a 53-year-old man affected by palmo-plantar slight psoriatic dermatitis, who presented a rapid onset of POPP. Rx imaging showed enthesitis and a moderate phalanx erosion with articular spaces narrowing and swollen periosteal reaction. A magnetic resonance imaging test of the hands showed an initial stage of synovitis and extensive periostitis of the distal phalangeal tufts. The patient has been treated with oral methotrexate for a month with a rapid clinical improvement and pain reduction. As POPP at first manifests as a painful onycodistrophy, it can easily be confused with bacterial perionyxis. The delay in making the correct diagnosis, and therefore, the delay in giving a proper treatment would mean the progressive articular erosion and the permanent invalidation of the patient's ability to use his hands.

Introduction

Psoriatic arthritis (PsA) is a chronic inflammatory disease characterized by the association of arthritis and psoriasis.[1] PsA is one of the subsets of seronegative arthropathies that share clinical features, including asymmetrical and oligoarticular joint involvement, a similar incidence in men and women, the same occurrence rate of dactylitis and enthesitis, negative rheumatoid factor and anti-cyclic-citrullinated-peptide antibody, and extra-articular manifestations such as onychitis and iritis. The spectrum of joint inflammation in PsA is wide, ranging from axial to peripheral disease, synovial and adjacent soft tissue inflammation, enthesitis, osteitis, new bone formation and severe osteolysis, and overlaps of all of these.[2] In comparison with rheumatoid arthritis (RA) patients, PsA patients show deeper joint changes. Furthermore, bone proliferation is more common and tenosynovitis is less frequent in PsA than in RA. Psoriatic onycho-pachydermo-periostitis (POPP) is considered a rare form of PsA, which is extremely painful and debilitating.[3] The first step for a successful treatment is to recognize POPP as a manifestation of PsA and to treat the disease with immunosuppressive therapy as soon as possible.

Case Report

A 53-year-old construction worker, suffering from slight palmo-plantar psoriasis for many years, came to our attention for the sudden onset (2 months) of onychodistrophy, onycholysis, and swollen painful hands and feet digits. He had been treated by his medician for at least 2 months with topical antibiotics for bacterial perionyxis. Then, he went to a dermatologist who gave him other topical treatments and oral therapy for the pain for weeks. When he arrived at our department, clinically he presented erythematous and desquamative lesions in his feet and hands, associated with erosions and rhagades [Figure 1]. The palms showed hyperkeratotic indurated horny plugs [Figure 1b]. Lesions of the soles appeared well demarcated by an erythematous peripheral ring [Figure 2]. Both the lesions were associated with intense perionyxis and edema of the distal phalanges. Dystrophy of the nails was characterized by abnormal hyperkeratosis which made them similar to ostraceous shells [Figure 1a]. The lesions were so painful that the patient was unable to work. He did not have fever. Mycological examination was negative. We performed radiographic examination of feet and hands. Feet Rx showed enthesitis and slight erosions of the terminal phalanges, with narrowed intra-articular spaces. There was also edema of the periarticular soft tissue. Hands Rx was similar, but articular damage was more relevant. Magnetic resonance imaging (MRI) of the hands showed extensive synovitis and periostitis of the distal phalangeal tufts. Laboratory investigation did not show any abnormality and rheumatoid factor was negative. Considering the clinical data such as association with psoriasis, painful enthesitis-synovitis, nail damage and negative rheumatoid factor, we finally made a diagnosis of POPP. The patient was treated with methotrexate (12.5 mg per os/week) for 21 days with a brilliant resolution of the lesions and symptoms [Figure 3]; then, methotrexate dosage was slowly decreased (2.5 mg every 2 months). Now, the patient is under a maintenance dosage (2.5 mg/week) in order to avoid relapses.

Figure 1

Hyperkeratosis and onycholysis of hands, fingers with soft tissue swelling of the terminal phalanx. Severe onychodistrophy with ostraceous nails are seen

Figure 2

Erythematous scaly lesions with rhagades and erosions. Dystrophy of nails is similar to that of the hands

Figure 3

Methotrexate treatment improved the patient's onycholysis and painful erythematous swelling of the terminal phalanx. Nails still present with scales but appear thinner

Discussion

POPP was first described in 1989 as a rare form of PsA.[3] It is characterized by onycodistrophy, onycolysis, connective tissue thickening above the distal phalanx and periosteal reaction leading to deformity of the digits.[3] A possible pathogenetic mechanism could be an inflammation starting from subungueal structures and spreading between tendons and bones of the terminal phalanx.[4] A hypothesis is that enthesitis arises at sites of high shear and compression forces, with the additive interaction between mechanical stress, microtrauma, tissue repair mechanism and bacterial molecules, variably leading to inflammation.[4] This model could suggest a possible explanation for the observation that PsA (and secondly POPP) may be associated occasionally with a preceding joint injury.[56] Further, there may be a link to the skin component as injury to the skin is known to be a factor in expression of psoriasis.

Considering POPP, the possible clinical differential diagnosis includes ungueal mycosis, Reiter's syndrome, Hallopeau syndrome, Bazex acrokeratosis. Most important differential diagnoses are for dermatophytosis that can show a very similar clinical manifestation and Candida infection characterized by painful paronychia. In our case, we could easily exclude this infection because of the negative mycological microscopic and cultural examination. In Reiter's syndrome, involvement of nails is very similar to that in POPP, but this syndrome is a genetically determined, often protracted host response to specific preceding enteric or genitourinary infection. It is usually characterized by an abruptly appearing, reactive, asymmetric inflammation of the synovium and periarticular tissue, accompanied by mucocutaneous, ophthalmic and genitourinary involvement. Hallopeau acrodermatitis is a sterile pustular eruption of the fingers, which slowly extends proximally. Final stages of this disease could be similar to that of POPP lesions, but POPP has no pustular lesions, and nail changes are characterized by hyperkeratosis rather than dystrophy or onycholysis. We could exclude Bazex acrokeratosis because of the localization of the lesions to hands and feet (Bazex syndrome usually also involves ears, nose, cheeks, elbows and knees). Furthermore, Bazex syndrome is associated with neoplasia of the upper respiratory tract, while our patient was in a good health condition. In RA, excessive ridging and sometimes beading of the nails are observed. When RA is associated with psoriasis, any of the nail changes found in the latter disease may be present.

POPP diagnosis is made by X-ray examinations, ultrasonography (US) and MRI, with MRI being considered as the golden standard.[7] Both US and MRI are more sensitive for visualization of inflammatory and destructive changes in patients’ fingers and toes because they have a major potential for improved examination of joints, tendons, and entheses in fingers and toes of patients with PsA.

Treatment for POPP is not standardized; mainly, the medications commonly used for PsA.[5] POPP is usually treated with low-dose methotrexate or anti-tumor necrosis factor (anti-TNF) medications, although methotrexate's traditional role as a first-line agent for moderate to severe psoriasis is being challenged by the rapid growth and use of biological therapies. Nowadays, the question remains whether most biological therapies have superior efficacy than the traditional systemic agents such as methotrexate in a short time. However, the significant cost differential and the current lack of long-term safety data for biological agents means that drugs such as methotrexate are likely to remain one of the first-line choices for the future treatment of PsA localized forms (and therefore for POPP). Considering that our patient had never been treated for psoriasis and the lesions were limited to hands and feet, we started therapy with methotrexate rather then biological therapy. The rapid resolution, either of the clinical lesions or the pain, confirms that POPP should be recognized as a specific entity in the spectrum of PsA, as shown by other similar cases in literature.[56] In view of POPP being considered as a subtype of PsA, it is easy to understand that not only immunosuppressive treatment is useful but also it is mandatory to stop disease progression that could otherwise lead to severe and destructive arthritis.

So, finally, we underline the importance of an accurate and rapid diagnosis and an immediated therapy of POPP disease, which is a subset of PsA with a rapid evolution that can be easily mistaken even by specialists.