Image Quizzes

Right ankle pain and swelling

Reviewed by Herbert S. Diamond, MD

Fiona McQueen, Marissa Lassere and Mikkel Ƙstergaard/Arthritis Research & Therapy

A 42-year-old woman with a 20-year history of plaque psoriasis presents with complaints of a 3-month history of pain, tenderness, and swelling in her right ankle and foot, of unknown origin. Physical examination reveals active psoriasis, with a Psoriasis Area and Severity Index (PASI) score of 6.7 and psoriatic nail dystrophy, including onycholysis, pitting, and hyperkeratosis. Tenderness and swelling are noted at the back of the heel. The patient denies any other complaints. Laboratory tests are normal, including negative rheumatoid factor and antinuclear factor. MRI reveals soft tissue and bone marrow edema below the Achilles insertion.

What is the diagnosis?





This patient's findings are consistent with a diagnosis of psoriatic enthesitis.

Enthesitis is a hallmark manifestation of psoriatic arthritis (PsA). Approximately 30% of patients with psoriasis are estimated to be affected by PsA, which belongs to the spondyloarthritis (SpA) family of inflammatory rheumatic diseases.

An enthesis is an attachment site of ligaments, tendons, and joint capsules to bone and is a key inflammatory target in SpA. It is a complex structure that dissipates biomechanical stress to preserve homeostasis. Entheses are anatomically and functionally integrated with bursa, fibrocartilage, and synovium in a synovial entheseal complex; biomechanical stress in this area may trigger inflammation. Enthesitis is an early manifestation of PsA that has been associated with radiographic peripheral/axial joint damage and severe disease, as well as reduced quality of life.

Enthesitis can be difficult to diagnose in clinical practice. Symptoms include tenderness, soreness, and pain at entheses on palpation, often without overt clinical evidence of inflammation. In contrast, dactylitis, another hallmark manifestation of PsA, can be recognized by swelling of an entire digit that is different from adjacent digits. Fibromyalgia frequently coexists with enthesitis, and it can be difficult to distinguish the two given the anatomic overlap between the tender points of fibromyalgia and many entheseal sites. Long-lasting morning stiffness and a sustained response to a course of steroids is more suggestive of enthesitis, whereas a higher number of somatoform symptoms is more suggestive of fibromyalgia.

Enthesitis is included in the Classification Criteria for Psoriatic Arthritis (CASPAR) as a hallmark of PsA. While it can be diagnosed clinically, imaging studies may be required, particularly in patients in whom symptoms may be difficult to discern. Evidence of enthesitis by conventional radiography includes bone cortex irregularities, erosions, entheseal soft tissue calcifications, and new bone formation; however, entheseal bone changes detected with conventional radiography appear relatively late in the disease process. Ultrasound is highly sensitive for assessing inflammation and can detect various features of enthesitis, such as increased thickness of tendon insertion, hypoechogenicity, erosions, enthesophytes, and subclinical enthesitis in people with PsA. MRI has the advantage of identifying perientheseal inflammation with adjacent bone marrow edema. Fat-suppressed MRI with or without gadolinium enhancement is a highly sensitive method for visualizing active enthesitis and can identify perientheseal inflammation with adjacent bone marrow edema.

Delayed treatment of PsA can result in irreversible joint damage and reduced quality of life; thus, patients with psoriasis should be closely monitored for early signs of its development, such as enthesitis. A thorough evaluation of the key clinical features of PsA (psoriasis, arthritis, enthesitis, dactylitis, and spondylitis), including evaluation of severity of each feature and impact on physical function and quality of life, is encouraged at each clinical encounter. Because patients may not understand the link between psoriasis and joint pain, specific probing questions can be helpful. Screening questionnaires to detect early signs and symptoms of PsA are available, such as the Psoriasis Epidemiology Screening Tool (PEST), Psoriatic Arthritis Screening and Evaluation (PASE) questionnaire, and Toronto Psoriatic Arthritis Screening (ToPAS) questionnaire. These and many others may be used to help dermatologists detect early signs and symptoms of PsA. Although these questionnaires all have limitations in sensitivity and specificity for the diagnosis of PsA, their use can still improve early diagnosis.

The treatment of PsA focuses on achieving the least amount of disease activity and inflammation possible; optimizing functional status, quality of life, and well-being; and preventing structural damage. Treatment decisions are based on the specific domains affected. Nonsteroidal anti-inflammatory drugs and corticosteroid injections are first-line treatments for enthesitis. Early use of tumor necrosis factor inhibitors (TNF) (adalimumab, certolizumab pegol, etanercept, infliximab, and golimumab) is recommended. Alternative biologic disease-modifying agents are indicated when these TNF inhibitors provide an inadequate response. They include ustekinumab (dual interleukin [IL]-12 and IL-23 inhibitor), secukinumab (IL-17A inhibitor), and apremilast (phosphodiesterase-4 inhibitor) and may be considered for patients with predominantly entheseal manifestations of PsA or dactylitis. Biological disease-modifying agents approved for PsA that have shown efficacy for enthesitis include ixekizumab (which targets IL-17A), abatacept (a T-cell inhibitor), guselkumab (monoclonal antibody), and ustekinumab (monoclonal antibody). Tofacitinib and upadacitinib, both oral Janus kinase inhibitors, may also be considered.

Herbert S. Diamond, MD, Professor of Medicine (retired), Temple University School of Medicine, University of Pittsburgh; Chairman, Department of Medicine Emeritus, Western Pennsylvania Hospital, Pittsburgh, PA.

Herbert S. Diamond, MD, has disclosed no relevant financial relationships.

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