A 53-year-old man without any history of trauma, presented with gradually increasing left-shoulder discomfort and swelling for few months. Clinical examination revealed a prominent swelling on the anterior aspect of the shoulder with discolouration of the overlying skin. Pain was felt on shoulder abduction.
Plain radiograph (Fig. 1) demonstrated conglomerate of multiple calcific densities around the greater tuberosity, with further similar densities projected over the scapula. There was no cortical expansion, bony destruction or periosteal reaction. The glenohumeral and acromioclavicular joints looked preserved. The subsequent CT (Fig. 2) revealed extensive hyperostosis appearing as ‘multiple dollops’ on the anterior surface of the scapular blade, with endosteal extension obliterating the medullary cavity of the scapula blade. There were also large masses of peri-articular calcific densities demonstrating mature cortex in the adjacent soft tissues, seen supero-laterally to the greater tuberosity, suggestive of heterotopic ossification. On MRI (Fig. 3), the dollops of cortical hyperostosis were expectedly demonstrated as low-signal abnormalities. The heterotopic ossified soft tissue masses also appeared as signal void on all sequences of the MR (Fig. 4), and were found to be within and beneath the deltoid muscle. There was surrounding soft tissue oedema, but no collection or haemorrhage. Apart from minimal subacromial bursal fluid, there were no other relevant findings like rotator cuff pathology or another lesion to explain patient’s symptoms.
This case was referred and subsequently discussed at the regional tertiary level soft tissue sarcoma centre. On review of all imaging, it was apparent that there were two separate pathologies at play in this case 1) heterotopic ossification (Fig. 1) which was the likely cause of clinical symptoms and 2) melorrheostosis (Figs. 2, 3) causing the incidental changes at the scapula. Our focus in this case report is on melorrheostosis. Melorheostosis, an uncommon non-hereditary sclerosing mesenchymal dysplasia of the bone, was first reported by Léri and Joanny in 1922 [1]. Aetiology is still unknown, but the pathogenesis is hypothetically attributed to genetic mutation involving the spinal sensory nerves of a sclerotome distribution [2]. Clinical symptoms range from being asymptomatic to having pain, stiffness or movement restriction. Although the radiology can look peculiar on first encounter, it is important to recognise this condition due to its mostly indolent nature. It usually affects the long bones on one side of the body, which on plain film has been classically described as “dripping candle wax”. However, it has also been described in flat bones, including the ribs and spine [3]. However, it is worth noting that there have been five different radiological appearances for melorheostosis described in the literature: 1) classic dropping wax appearance 2) osteoma-like lesion 3) myositis ossificans-like lesion 4) osteopathia striata-like lesion and 5) mixed picture. [4] For the changes at the scapula, differentials of osteoma, sessile osteochondromas, parosteal osteosarcoma and osteopathia striata were considered, but all these were thought to be less likely. Osteomas are predominantly found in the paranasal sinuses. Osteochondromas would have demonstrated cartilaginous cap on MRI, lack of a lucent centre went against paraosteal osteosarcoma and osteopathia striata cause vertical striations in the bone, but do not usually cause cortical hyperostosis. Above all, none of these conditions would have explained the concurrent heterotopic ossification found in this case. Due to the combination of myositis ossificans-like heterotopic ossification in the periarticular region and fairly typical radiological findings in the scapula [5], a diagnosis of melorheostosis was reached. The patient was further followed over a six-month period, during which the symptoms settled down and the radiological findings remained static. The overarching histological feature of melorheostosis is excess bone formation [6]. The long tubular bones most typically show the characteristic appearance of a dripping candle wax possibly because of their orientation, physical shape or gravity, allowing the areas of hyperostosis to drip along the length of the bone. However, for flat bones, instead of dripping like candle wax, flat geometry perhaps acts to reduce the effect of gravity, thereby encouraging the hyperostosis to accumulate like dollops along the periosteal surface of the bones [7]. Without taking the liberty of imagination, we are describing this feature on cross sectional imaging (Figs. 2 and 3) as a ‘dumpling on a plate sign’ (Fig. 5). Such an appearance may also be expected in similarly oriented flat bones. The characteristic melting dripping wax sign is not seen in all patients [8] and it may not be feasible for all radiologists to instantly recall the differing radiological patterns [4] seen in such a rare bone dysplasia like melorheostosis. We hope this sign will equip the radiologist’s memory with an another visually striking and relatable sign, along with the “dripping candle wax”, to help them diagnose this condition. Written informed patient consent for publication has been obtained.
Melorheostosis
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1. X-ray plain film (Figure 1) shows: a significant increase in soft tissue density near the left shoulder joint, forming a mass-like ossification shadow with an irregular distribution, suggesting bony overgrowth or heterotopic ossification around the joint. The scapular region presents localized cortical thickening and accumulation, with maintained continuity at the margins and no apparent signs of bone destruction.
2. CT (Figure 2) demonstrates: a mass-like high-density sclerotic lesion protruding from the scapular surface, suggestive of cortical hyperplasia or an osteogenic change, and heterotopic ossification is also visible within the local soft tissue.
3. MRI (Figures 3, 4) shows: the abnormal signal on the surface of the scapula mainly presents as a low to intermediate signal (T1/T2) sclerotic lesion, and the irregularly distributed strip-like ossification within the surrounding soft tissue is also observed. Compared to the typical “dripping candle wax” appearance, the thickening on the scapula tends to present as a “mass-like” or a “dumpling on a plate” accumulation pattern, referred to as the “dumpling on a plate sign.”
Based on the patient’s clinical presentation and imaging findings, the following differential diagnoses can be considered:
1. Heterotopic Ossification: The presence of bone formation within the soft tissues indicates prominent heterotopic ossification, possibly related to repeated shoulder stimulation or unclear soft tissue pathology; however, this alone may not fully explain the abnormal sclerosis on the scapular surface.
2. Osteoma: Commonly found in the skull and paranasal sinuses. Although an isolated osteoma may occur in the scapula, the typical manifestation is not widespread cortical thickening as seen in this case, and the findings here are more extensive.
3. Osteochondroma: A cartilage cap would usually be visible on MRI, but this case lacks the typical cartilage cap structure.
4. Sclerosing Bone Diseases (e.g., Osteopathia Striata): May cause longitudinal striations of bone sclerosis, but they usually manifest as vertical stripes rather than localized protrusive bony proliferation.
5. Malignant Tumor (e.g., Parosteal Osteosarcoma): Typically presents as extensive tumor growth adjacent to the bone cortex, with associated soft tissue mass and signs of destruction. No significant destructive changes are observed in this case, making this diagnosis less likely.
Considering the scapular surface “mass-like” sclerosis and concurrent heterotopic ossification around the shoulder, and with reference to reports describing similar presentations in melorheostosis, the pathological features are most consistent with the coexistence of heterotopic ossification and melorheostosis.
Taking into account the imaging characteristics (not the typical “dripping candle wax” but showing “mass-like” sclerotic thickening on the scapula) and clinical presentation, and excluding other common diagnoses, the most likely diagnoses are:
1) Heterotopic ossification of the shoulder joint and surrounding soft tissue
2) Melorheostosis in the scapular region.
Because the patient’s symptoms are gradually improving and the imaging findings are relatively stable, conservative treatment and regular follow-up are recommended initially. If significant functional impairment or suspicion of malignancy arises in the future, a biopsy or further evaluation may be warranted.
1. Conservative Treatment:
- For mild shoulder swelling and pain, NSAIDs (non-steroidal anti-inflammatory drugs) can be used to reduce pain and inflammation.
- Regular imaging follow-up is advised to monitor any progression in the extent of sclerosis or ossification.
- If severe heterotopic ossification in the soft tissue markedly affects joint mobility, low-dose radiotherapy or medication (to inhibit heterotopic bone formation) under specialist assessment may be considered.
2. Physical Therapy and Rehabilitation:
- Initial phase (after acute symptoms subside): gentle passive stretching and mild active exercises within the joint range, such as pendulum exercises for the shoulder, to maintain basic range of motion. A frequency of three sessions per week, each lasting 15–20 minutes, is recommended.
- Stable phase: begin strengthening exercises for the shoulder muscles using resistance bands (e.g., abduction, internal rotation, external rotation). Perform 3–5 sessions per week, each 20–30 minutes, at an intensity that induces mild soreness but not significant pain.
- Advanced phase: gradually introduce higher-load functional training for the shoulder muscles (e.g., light dumbbells or gym machines), ensuring proper technique and avoiding excessive stretching or high-impact motions. Progress to about 4–5 sessions a week, each around 30 minutes, depending on individual tolerance.
- Patients with fragile bones or compromised cardiopulmonary function should increase activity gradually under the guidance of professional medical or rehabilitation staff, closely monitoring for pain or discomfort.
3. Surgical Intervention:
- If heterotopic ossification or bony overgrowth severely restricts joint function or causes neurovascular compression, surgical resection or corrective procedures may be considered.
- Postoperative rehabilitation must be strictly followed to prevent recurrent heterotopic ossification or joint adhesions.
This report is a reference-based medical analysis derived from current imaging and historical data and does not replace in-person consultation or a comprehensive evaluation by a professional physician. Specific treatment plans must be confirmed in conjunction with clinical examination, laboratory results, and pathological evidence, and finalized by qualified healthcare professionals.
Melorheostosis
