Differential Diagnosis of Sudden-Onset Shoulder Pain in a 58-Yr-Old Male Patient With an Elevated C-Reactive Protein

PATIENT INFORMATION A 58-yr-old man with no significant medical history visited the orthopedic surgery department of a university hospital because of sharp, sudden-onset right shoulder pain for 5 days. He reported nonradiating pain in the lateral shoulder area around the greater tubercle. The pain had a severity score of 8/10 on a Numeric Rating Scale that significantly affected his sleep. The pain was sharp and aggravated when the patient abducted his right arm. The pain was not exacerbated by neck motion. Moreover, there were no precipitating factors, such as trauma, heavy work, or previous injections to the right shoulder area. One year prior, the patient had intermittent right shoulder pain (pain degree: Numeric Rating Scale 1–2); however, it was well managed with oral pain medications (acetaminophen 650 mg/d). Before visiting our hospital, the patient visited the local hospital 4 days after the onset of the sharp pain. Laboratory tests at the local hospital performed 4 days after pain onset revealed elevated C-reactive protein (CRP) levels (4.4 mg/dl; reference range = 0.3–1 mg/dl). The physician at the local hospital suspected septic arthritis of the right shoulder joint. The following day (5 days after pain onset), the patient was referred to this hospital for further evaluation and management. CLINICAL FINDINGS The patient’s body temperature at presentation in our hospital was 36.7°C. Tenderness over the right greater tubercle and warmth around the greater tubercle were noted; however, no swelling or erythema was observed. During active and passive range of motion of the right shoulder joint, pain increased. When the patient abducted his right shoulder over 60 degrees, the patient’s pain was most severely aggravated as compared with that during internal and external rotation, adduction, flexion, and extension. In addition, the patient had right shoulder pain even in the resting state. During passive internal and external rotation and adduction, no limitation of motion was observed. However, passive abduction range of motion could not be assessed because of severe pain. No sulcus sign was observed. No weakness was observed in right elbow flexion, elbow extension, wrist extension, and finger flexion. Motor examination of his right shoulder could not be performed against resistance because of pain. There were no sensory deficits in his right upper extremity. The biceps and triceps muscle stretch reflexes were normal on both sides. Spurling sign was negative. This study conforms to all AJPMR RFS CARE guidelines and reports the required information accordingly (see Supplemental Checklist, Supplemental Digital Content 1, https://links.lww.com/PHM/B266). What is your differential diagnosis for the patient’s shoulder pain? What diagnoses do you need to rule out? What is the most likely diagnosis? DIAGNOSTIC ASSESSMENT Blood tests revealed an elevated CRP level (6.159 mg/dl; reference range = 0.3–1 mg/dl) and erythrocyte sedimentation rate (92 mm/H; reference range = 0–25 mm/H). The white blood cell count (8190 cells/μl, neutrophils = 64.4%; reference range = 4000–10,000 cells) and procalcitonin level (0.037 ng/ml; reference range = 0–5 ng/mL) were within the reference ranges. The uric acid level was also normal (4.3 mg/dl; reference range = 2.2–7.8 mg/dl). We considered the following disorders as possible causes of sudden unilateral shoulder pain: Septic arthritis: This was considered, given the elevated CRP level and the development of sudden, severe pain. In addition, warmth around the shoulder joint supports this diagnosis. Although our patient was afebrile and had a normal white blood cell count range, septic arthritis could not be ruled out because septic arthritis can occur without fever or leukocytosis.1 Gouty arthritis: In the case of acute monoarthritis, gouty arthritis should be considered along with septic arthritis. A significantly elevated CRP level supports this diagnosis.2 Although the serum uric acid level was normal in our patient, gouty arthritis could not be ruled out. Approximately 60% of patients with acute gout attacks have normal serum uric acid levels.2 However, gouty arthritis rarely develops in the shoulder joint. Calcific tendinitis: Sudden onset of severe pain with worsening of pain with shoulder movements, resting pain, and tenderness over the greater tubercle support the possibility of this disorder. In addition, the CRP level can be increased in severe cases.3,4 Adhesive capsulitis: This diagnosis is possible, however, it usually develops more gradually.5 In addition, patients with this disorder have limitations of motion in abduction and external rotation. Rotator cuff tear: This disorder can induce weakness in abduction and external rotation of shoulder muscles.6 In our patient, the presence of weakness could not be exactly checked because of severe pain. However, this disorder usually causes pain during shoulder movement in a specific direction, but not at rest. In addition, the CRP level is usually not elevated. Therefore, in our patient, the possibility of this diagnosis is low. Fracture or dislocation: The absence of a trauma history makes this diagnosis significantly less likely. Polymyalgia rheumatica: This disorder causes sudden onset of severe shoulder pain and increased CRP level.7 However, in most cases, bilateral shoulder joints are involved. Therefore, it is highly unlikely that our patient had this disorder. Overall, the most likely disorders are septic arthritis, gouty arthritis, and calcific tendinitis, so imaging studies were performed. Plain radiographs of the right shoulder in the anterior-posterior view showed the largest calcific deposit, measuring 1.0 × 1.7 cm above the greater tubercle of the right humerus (Fig. 1). On the axial view of the plain radiograph, calcific deposits were located near the superior and middle facets of the greater tubercle. Based on plain radiography findings, we suspected calcific tendinitis of the supraspinatus tendon.FIGURE 1: Plain radiographs of the right shoulder in the anterior-posterior (A) and axial (B) views showing the largest calcific deposit, measuring 1.0 × 1.7 cm (arrows), above the greater tubercle of the right humerus.For precise localization and identification of the extent of the lesion, magnetic resonance imaging was obtained (Fig. 2). All pulse sequences presented low-signal lobulated lesions near the greater tubercle of the right humerus, which demonstrated calcification. Magnetic resonance images revealed a lobulated calcification in the supraspinatus tendon near the greater tubercle (insertion area; Fig. 2). Lobulated tendon calcifications that migrated into the subdeltoid bursa and increased bursa effusion with surrounding soft tissue edema were also observed. All these magnetic resonance imaging findings demonstrated calcific tendinitis in the supraspinatus tendon and migration of calcification into the bursa, inducing calcific bursitis.FIGURE 2: Magnetic resonance imaging of the right shoulder. A, Axial gradient echo, (B) oblique coronal T1-weighted, and (C) oblique sagittal proton density fat-saturated images showing calcification (arrows) in the supraspinatus tendon near the greater tubercle of the right humerus. Lobulated tendon calcifications migrating into the subdeltoid bursa and increased bursal effusion with surrounding soft tissue edema can also be observed.The primary diagnosis was calcific tendinitis at the right supraspinatus tendon with calcific bursitis. How would you manage calcific tendinitis with calcific bursitis? THERAPEUTIC INTERVENTION Nonsteroidal anti-inflammatory drug (Melodex, Meloxicam 7.5 mg twice daily) was administered. FOLLOW-UP AND OUTCOMES The patient’s shoulder pain completely disappeared 2 days after the initial oral medication. The oral medication was administered for another 1 wk. At 1- and 2-mo follow-up after the onset of severe shoulder pain, the patient reported that his pain did not recur. DISCUSSION In clinical practice, when a patient presents with sudden onset of unilateral shoulder pain with elevated CRP levels, clinicians usually suspect septic arthritis. Septic arthritis is an important differential diagnosis requiring urgent treatment because it can cause devastating complications in patients. Some clinicians consider the possibility of gouty arthritis; however, because of its rare development in the shoulder joint, it is considered less often than septic arthritis.8 Likewise, in our case, the physician at the local hospital referred the patient to our university hospital given the suspicion of septic arthritis. C-reactive protein level is a widely used marker of inflammatory conditions, such as infection, rheumatoid arthritis, gout attack, chronic inflammatory musculoskeletal diseases, and some cardiovascular diseases.9 Especially in bacterial infection, the CRP level is markedly elevated. In calcific tendinitis, although the exact percentage of patients who show elevated CRP levels has not been evaluated, some previous studies reported cases of calcific tendinitis with highly elevated CRP levels.3,4 Calcific tendinitis results from calcium hydroxyapatite crystal deposition in any tendon of the body. However, it most commonly occurs in rotator cuff tendons, and the incidence of shoulder pain from calcific tendinitis is reported to be approximately 7%.3 It becomes acutely symptomatic when calcium hydroxyapatite crystals pass through the tendon into an adjacent bursa,4 producing an inflammatory response. Inflammation increases the CRP level and causes severe and disabling pain, which mimics septic arthritis.3,4 Calcific tendinitis is usually a self-limiting condition and, in most cases, can be treated with oral pain medications. If the pain is not well controlled with oral medications, extracorporeal shock wave therapy, subacromial steroid injection, ultrasound-guided percutaneous lavage, and iontophoresis can be applied.10 CONCLUSIONS When a patient develops acute atraumatic shoulder pain that is present at rest and during movement, clinicians should consider the possibility of calcific tendinitis. The elevation of CRP levels can be a supportive finding for the diagnosis of calcific tendinitis. In addition, before confirming the diagnosis, differential diagnosis should be conducted; septic arthritis and gouty arthritis should be ruled out with imaging studies including radiography, magnetic resonance imaging, or ultrasonography.

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