Dermatology Online Journal

Psoriatic onycho-pachydermo periostitis
Monika Srivastava MD, Gary Solomon MD, Bruce Strober MD PhD
Dermatology Online Journal 13 (1): 20

New York University Department of Dermatology

---

Abstract

A 46-year-old woman presented with onycholysis and swollen, painful digits. No other stigmata of psoriasis were present. Magnetic resonance imaging of the hands showed an extensive periosteal reaction of the phalangeal tuft. Psoriatic onycho-pachydermo periostitis (POPP) is a rare subset of psoriatic arthritis that is characterized by psoriatic onychodystrophy, connective-tissue thickening above the distal phalanx, and a periosteal reaction. Treatment of POPP is difficult; however, low-dose methotrexate and anti-TNF-alpha agents may be beneficial. In patients who are unresponsive or intolerant of these medications, other biologic and non-biologic disease modifying anti-rheumatic drugs need to be considered.

---

Clinical synopsis

Figure 1

A 46-year-old woman with a past medical history of optic neuritis, Shigella infection, Raynaud phenomenon, nephrolithiasis, and asthma presented to New York University Dermatologic Associates in August 2004 with swollen fingers, morning stiffness, and nail changes. Family history was negative for skin diseases. After confirmation of the diagnosis with appropriate imaging studies, the patient was started on methotrexate 12.5 mg weekly. Despite increasing the dose of methotrexate to 17.5 mg, there was only minimal improvement of her joint symptoms. She was given a concurrent course of alefacept 15 mg with 12 intramuscular injections over 12 weeks that was ineffective. Subsequent treatment with etanercept 50 mg weekly had to be discontinued after 3 months, owing to the development of neuropathy. Her symptoms resolved and an electromyogram and magnetic resonance imaging studies showed no evidence of demyelinating disease. However, owing to a family history of multiple sclerosis in the patient's mother, the decision was made to exclude tumor necrosis factor (TNF)-α inhibitors as a therapeutic option. In January 2006 cyclosporin 3mg/kg was added to methotrexate 15 mg weekly. The patient did not tolerate cyclosporin, owing to nausea and fatigue. Furthermore, the patient's joint disease has continued to progress with involvement of more joints. Cyclosporin was discontinued. The patient was recently referred for a rheumatologic consultation for further evaluation and treatment options. She was started on 6-mercaptopurine 50 mg daily in addition to methotrexate and prednisone 5 mg daily. If she fails therapy with 6-mercaptopurine, trials of rituximab or abatacept will be considered.

Prominent nail pits and distal onycholysis were present on the fingernails and toenails. The scalp, face, chest, back, extremities, and groin were clear. Diffuse thickening of the flexor tendons of the hands was noted. Tenderness of 18 metacarpophalangeal and proximal interphalangeal joints and the greater trochanters was present. The range of motion was decreased in the right shoulder and the spine.

Figure 2	Figure 3

A complete blood count, electrolytes, and liver function tests were normal. A magnetic resonance imaging test of the hands showed extensive periostitis of the distal phalangeal tufts.

Comment

Psoriatic onycho-pachydermo-periostitis (POPP) was initially described in 1989 [1]. It is considered to be a rare form of psoriatic arthritis that is characterized by psoriatic onychodystrophy, onycholysis, connective-tissue thickening above the distal phalanx, and a periosteal reaction [1]. These nail, bone, and connective-tissue changes clinically result in a drumstick-like deformity of the digits. Patients usually have associated tenderness of the involved joints, with functional impairment. Any of the nails can demonstrate onycholysis; however, in most cases the great toes are involved [2].

Although POPP is considered to be a type of psoriatic arthritis, its pathology and pathophysiology are poorly understood. In at least seven of the reported cases of POPP, HLA-B27 was found to be present, which suggests a similarity between POPP and other spondyloarthropathies [3]. It has been theorized that in spondyloarthropathies primary inflammation from the enthesis is transmitted to articular structures and results in pathology [4]. It is possible that a parallel mechanism occurs in POPP, in which inflammation spreads from subungual structures through fibrous areas between tendon and bone to the terminal phalanx.

Treatment of POPP is difficult. Therapy is based on clinical experiences with psoriatic arthritis. Responses to nonsteroidal anti-inflammatory medications and sulfasalazine are inconsistent, and they are often ineffective [3]. A recent report demonstrated the efficacy of methotrexate 4 mg weekly in one patient [5]. A clinical and radiologic resolution of POPP was reported in a patient treated with adalimumab for 4 months [3].

Treatment options become even more difficult when contraindications exist to the use of certain promising medications. Our patient had a family history of multiple sclerosis in her mother. Although a short trial of etanercept was attempted, neurologic side effects made the use of TNF-α inhibitors impossible. Furthermore, the patient also failed treatment with alefacept. Other disease modifying anti-rheumatic drug therapies that included methotrexate and cyclosporin were either ineffective or intolerable.

In this setting where the patient has failed or been intolerant to more traditional therapies, other medications which have been successful in the treatment of psoriatic arthritis or rheumatoid arthritis need to be considered. The patient is currently being treated with 6-mercaptopurine. One study indicated that eleven of thirteen patients with psoriatic arthritis treated with 6-mercaptopurine showed improvement in skin and joint disease within 3 weeks of initiating therapy at a dose of 1mg/kg with minimal side effects [6]. Leflunomide is another disease modifying anti-rheumatic drug which has shown efficacy in the treatment of psoriatic arthritis [7].

Newer therapies which are approved for the treatment of rheumatoid arthritis that are being considered as treatment options in this patient include abatacept and rituximab. Abatacept is a costimulation modulator that prevents the full activation of T-cells. Rituximab is a chimeric monoclonal antibody against CD20+ B-lymphocytes. Both of these medications have demonstrated efficacy in patients with rheumatoid arthritis, even those who have failed treatment with TNF-α inhibitors [8, 9].

References

1. Fournie B, et al. Psoriatic onycho-pachydermo-periostitis of the big toe: anatomo-clinical study and physiopathogenic approach apropos of 4 cases. Rev Rhum Mal Osteoartic 1989; 56:579

2. Goupille P, et al. Incidence of osteoperiostitis of the great toe in psoriatic arthritis. J Rheumatol 1996; 23: 1553

3. Bongartz T, et al. Successful treatment of psoriatic onycho-pachydermo periostitis (POPP) with adalimumab. Arthritis Rheum 2005; 52: 280

4. McGonagle D, et al. Psoriatic arthritis: a unified concept twenty years on. Arthritis Rheum 1999; 42: 1080

5. Ochiai T, et al. Psoriatic onycho-pachydermo-periostitis successfully treated with low-dose methotrexate. Med Sci Monit 2006; 12: CS27

6. Baum J, et al. Treatment of psoriatic arthritis with 6-mercaptopurine. Arthritis Rheum 1973; 16:139

7. Liang GC, Barr WG. Long term followup of the use of leflunomide in recalcitrant psoriatic arthritis and psoriasis. Arthritis Rheum 2001; 44:S121

8. Westhovens R, et al. Improved health-related quality of life for rheumatoid arthritis patients treated with abatacept who have inadequate response to anti-TNF therapy in a double-blind, placebo-controlled, multicentre randomized clinical trial. Rheumatology 2006 [Epub ahead of print].

9. Brulhart L, et al. Efficacy of B-cell depletion in rheumatoid arthritis patients refractory to anti-tumour necrosis factor (TNF)- a agents an open label observational study. Ann Rheum Dis 2006 [Epub ahead of print].

© 2007 Dermatology Online Journal