PUSTULOTIC ARTHRO-OSTEITIS (SONOZAKI SYNDROME)

Abstract

Pustulotic arthro-osteitis, first described by Sonozaki, is a relatively rare disorder. Its prevalence is however probably underestimated in dermatological literature. Early recognition of the signs can prevent misdiagnosis. We describe a Turkish patient who presented with palmoplantar pustulosis and involvement of the sternoclavicular joint and peripheral oligoarthritis.

Introduction

Pustulotic arthro-osteitis (PAO) was first described by Sonozaki.It is a relatively rare disease. Early recognition of this condition can prevent misdiagnosis and mismanagement.

Case Report

A 53-year-old woman was admitted to our department in February 2007 with a pustular rash affecting the palms and soles. Inflammation and swelling of the small joints and right-sided low back pain developed during hospitalization. The patient had no history of psoriasis and there was no history or clinical evidence of psoriasis in her family.

On physical examination, sharply demarcated erythematosquamous lesions with groups of sterile pustules were seen on the palms and soles [Figures 1 and 2]. There was diffuse swelling and erythema over the right sternoclavicular, the right wrist and the left ankle joints. While there was pain on palpation, the range of motion was normal. General physical examination was normal.

Figure 1.

Pustular lesions on the right palm

Figure 2.

Pustular lesions on the medial sides of feet

Laboratory findings showed an erythrocyte sedimentation rate (ESR) of 120 mm/h (normal <20 mm/h) and C-reactive protein (CRP) of 6.44 mg/dL (normal<0.8 mg/dL). Serum was negative for rheumatoid factor and antinuclear factor, and anti-dsDNA, anti-Ro, anti-La, and anti-Sm antibodies were not present. HLA typing was negative for HLA-B51, 52, and 27. Biochemical screening showed no abnormality. A technetium-99m diphosphonate-labeled scintigram of bones revealed abnormal focal increases in tracer uptake in the right sternoclavicular and left ankle joints [Figure 3] Although x-ray of the wrist and the sternocostoclavicular region revealed soft tissue swelling, there was no ossification of the sternocostoclavicular region. There were bone erosions on the knees, hands, ankles, and elbows. A computed tomography scan showed sclerosis of the sacroiliac joints

Figure 3.

Whole-body bone scintigram

Skin biopsy from lesions on the left hand showed spongiosis and dyskeratotic cells in the basal layer, with infiltration of polymorphonuclear cells under the orthokeratotic epidermis. A dense dermal neutrophilic infiltrate was also present.

On the basis of these clinical and histopathologic features and the scintigram findings we made the diagnosis of PAO.

The patient was started on prednisone 1 mg/kg/day. After about 1 week of treatment, the swelling and pain in the affected joints had decreased, and the prednisone dose was tapered to 10 mg per day. During that time, new palmoplantar pustulotic lesions appeared. These new cutaneous manifestations improved with dapsone (50 mg/day). Complete clearance was achieved after 3 months of therapy. The patient is now healthy after 6 months follow-up and no maintenance treatment is required.

Discussion

Palmoplantar pustulosis is a skin disease characterized by recurrent eruptions of sterile pustules, with erythema and exfoliation. The lesions are situated exclusively, and often symmetrically, on the palms and/or soles.[1–3] The age of onset is usually 30–60 years, and males and females are affected equally. There is a relatively higher prevalence in Japan and the Scandinavian countries.[4] In Scandinavia, it occurs in 0.05% of the population.[1] On the other hand, PAO is a rheumatic syndrome of unknown etiology and is characterized by an inflamatory osteitis of the sternoclavicular joint along with palmoplantar pustulosis.[5] It was first described by Sonozaki and colleagues in 1979.[1] PAO or Sonozaki syndrome occurs in about 10%–30% of patients with palmoplantar pustulosis. Until a few years ago, this syndrome was considered to be a manifestation of psoriatic arthritis and was then erroneously classified by rheumatologists in the SAPHO (synovitis, acne, pustulosis, hyperostosis, osteitis) syndrome. Similar clinical features have been observed in patients with sternocostoclavicular hyperostosis (SCCH) and SAPHO. SCCH is a rare condition characterized radiologically by progressive hyperostosis of the medial ends of the clavicles, upper ribs, and sternum, together with soft tissue ossification between the upper ribs and clavicles. Clinically, the patients present with painful swelling of the sternum, clavicles, and upper ribs. SAPHO presents with anterior chest wall involvement, axial skeletal lesions, and osteitis of appendicular bones. Recently, the term acquired hyperostosis syndrome has been used.[6]

PAO is now classified as a member of the seronegative spondyloarthritis group of disease (which includes ankylosing spondylitis, Reiter's syndrome, and psoriatic arthritis); however, it is not associated with HLA-B27.[4] The principal lesion in PAO is sternoclavicular involvement, with lesions also occurring in the spinal column and the sacroiliac and peripheral joints.[2] Our patient had swelling of the sternoclavicular, right wrist, and left ankle joints, as well as low back pain. Sclerosis of ischial bone was established on computed tomography. Although our patient had osteoarthritis affecting the sternoclavicular region, right wrist, and left ankle, as shown by the bone scan, there were no obvious radiological changes. Arthritis of the sternoclavicular joint is most frequent in patients with PAO, but occurs in less than 15% of patients with ankylosing spondylitis, Reiter's disease, and psoriatic arthropathy.[6–8] In the majority of the cases, the arthritis is of seronegative mono- or oligo-arthritic type, as in our patient who had oligoarticular arthritis.[5,8] In PAO, the most commonly affected peripheral joints are the metacarpophalangeal joints, the proximal interphalangeal joints of fingers, and the elbow and knee joints. Other joints such as the hip, the ankle, and the wrist joints have also been involved rarely.[6] Our patient had ankle and wrist arthritis, but the knee joint was not involved.

PAO is characteristically non-erosive and transient and does not induce contracture deformities, and this was true in our patient also.[2,5] The interval between the onset of skin eruptions to the onset of arthro-osteitis is about 2 years in more than 70% of cases.[6]

In our patient, the sternoclavicular joint arthritis was preceded by skin eruption. Elevated CRP and ESR were the only significant laboratory abnormalities in our patient. The cause of these abnormalities, like the cause of the underlying disease process, remains unclear. Edlund et al. recently cultured Propionibacterium acnes from biopsy specimens of patients with this syndrome in approximately 50%.[5] No microorganisms were obtained in samples taken from the lesions of our patient. This agrees with the experience of other workers, who have also failed to isolate any specific microorganism from the bones or skin lesions of affected patients.[2,5,6] In PAO, the arthropathy is not associated with HLA-B27, and this was true in our patient also. To the best of our knowledge, HLA-B27 is related to generalized pustular psoriasis, psoriatic arthritis, ankylosing spondylitis, and Reiter's disease.[1]

X-ray findings have been consistently reported to be negative, except for soft tissue swellings in acute phases, as in our patient also.

PAO is considered as a member of the seronegative spondylo-arthritis group.[6] SAPHO was excluded because of the absence of synovitis, acne, and hyperostosis. SCCH could also be excluded because of the absence of hyperostosis. The presenting symptoms and findings in our patient, including palmoplantar pustulosis and arthro-osteitis, were compatible with Sonozaki syndrome or PAO.

The disease shows a chronic course with exacerbations and remissions over many years. Treatment is usually symptomatic and consists mainly of analgesics and nonsteroidal anti-inflammatory drugs such as phenylbutazone and indomethacin. Corticosteroids, colchicine, sulfasalazine, methotrexate, and cyclosporine have been used with variable success.[4,7] Dicloxacillin was found to be ineffective. Topical steroids, etretinate, and topical PUVA have been used for the pustular lesions on the palms and soles.[9] If the anterior chest wall symptoms are so severe as to interfere with the patient's daily activities, surgical resection of the clavicle is recommended.[7,8] Dapsone has both antibiotic as well as anti-inflammatory effects. In the case presented here, dapsone treatment was used successfully to treat the cutaneous manifestations and it also maintained the prolonged remission.

To the best of our knowledge, this is the first report of PAO from Turkey. PAO may easily be missed if clinical suspicion is not high. Radiological studies must be performed in a patient with palmoplantar pustulosis and swelling of joints to avoid missing the diagnosis.