24-year-old male with a history of severe pain in the heels and achilles from past 6 months

Discussion

Enthesitis of heel could be suspected in the current case due to the presence of disabling heel pain with substantial rest stiffness. This is one of the common conditions in active young patients and poses a diagnostic and management dilemma. It is significant to differentiate whether the condition is non-inflammatory (enthesopathy) or inflammatory (enthesitis). The presence of clinical features of inflammation like rest pain, improvement of pain after movement, and the presence of tenderness and/or swelling indicated the possibility of inflammatory enthesitis.

Enthesitis, defined as the inflammatory changes of an enthesis, is a characteristic finding in spondyloarthropathies (SpAs). Enthesis refers to the insertion of a tendon, ligament, capsule, or fascia into bone and it encompasses the inserted structure and the bone. The importance of enthesitis relative to synovitis, subchondral marrow inflammation, and osteitis in ankylosing spondylitis (AS) is debated. The different conditions that can cause pain in entesis include rheumatic disorders, spondyloarthropathies,  rheumatoid arthritis,  chondrocalcinosis osteoarthritis, diffuse idiopathic skeletal hyperostosis, metabolic and endocrine disorders, hyperparathyroidism, hypothyroidism, hypoparathyroidism, X-linked hypophosphatemia, acromegaly, hemochromatosis, ochronosis, familial hypercholesterolemia, diabetes mellitus, chronic renal failure, and entesitis caused by drugs (fluoride, fluoroquinolones glucocorticosteroids, and retinoids). ¹

Enthesitis is the primary clinical feature of spondyloarthritis. Pelvic enthesitis has a high specificity for confirming SpA and it can be diagnosed by MRI of sacroiliac joints.² The hallmarks of peripheral SpA are the development of enthesitis, most typically of the Achilles tendon and plantar fascia, and new bone formation.³ Enthesopathy is more common in subjects with  untreated celiac disease and positive anti-tissue transglutaminase antibodies titre when compared to those on gluten-free diet and absence of serum anti-tissue transglutaminase antibodies titre.⁴ The anterior chest wall (ACW) pain was seen in 45% of patients with complaints of inflammatory back pain (IBP). In patients with IBP suggestive of SpA, presence of ACW pain is associated with enthesitis, thoracic spine involvement, radiographic sacroiliitis, diagnosis of AS, and with a more severe disease. ACW pain could be interpreted as a diagnostic feature for AS.⁵ It is common finding in rheumatic diseases namely AS and Behcet's disease. Musculoskeletal complaints are common in patients with familial Mediterranean fever (FMF), and these could be one of the clinical manifestations of enthesopathy.^6-9 In a case series from India, 7 out of 11 patients with a typical presentation of Reiter's syndrome had enthesitis as one of their presentations.¹⁰ As per another series published from India, the most common sites of enthesitis were chondro-sternal junction (30%) and Achilles tendonitis (24.3%).¹¹ In enthesitis of elderly gout is one of the possibility.¹²

Thus in the presence of persisting enthesitis of heel, after excluding the possibility of post-traumatic enthesitis, it is important to rule out other differential diagnoses. The pain may be disabling and need attention and appropriate identification X-ray of the pelvis was done in the current case to exclude sacroiliitis (Fig 1.) X-ray of the heel of Achilles may indicate calcification at bony insertion suggesting enthesitis. Ultrasound examination or MRI imaging is recommended if associated tenosynovitis on neighbouring joints is suspected. Presence of conditions like hypercholesterolemia, hypothyroidism and other metabolic causes also needs be explored.

In the present case, the sacroiliitis was asymptomatic. The patient was HLA B 27 negative with normal inflammatory parameters. However, the patient cannot be categorised to have seronegative SpA, since he fulfilled the criteria of ESSG criteria only partially. The radiological features of sacroiliitis and enthesitis may assist in diagnosing ankylosing spondylitis in those who do not have inflammatory back symptoms. Although radiological features are present according to the New York criteria, the case cannot be categorized as AS since clinical features are absent. However, managing the patient with NSAID may help to improve the symptoms.

Table 2: Comparison of two criteria of seronegative SpA

Table 3:  New York criteria for diagnosing ankylosing spondylitis

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