Melorheostosis and Osteopoikilosis: A Review of Clinical Features and Pathogenesis

A rare case of monostotic Melorheostosis of right ulna presenting with chronic forearm pain - Case report

INTRODUCTION

Melorheostosis is extremely rare non-cancerous lesion of bone mainly affecting the long bones and soft tissues. The incidence is 0.9 per million population. It affects male and female equally and reported among children and early adulthood. Common symptoms include pain, deformity and restricted range of movement of affected joint.

CASE PRESENTATION

A 28-year-old female presented with pain at right forearm for nine months. The pain was of insidious onset and progressive in nature with severity of VAS 7/10. On examination, no gross deformity of right forearm was noted, no tenderness along the bones and range of movement of right elbow and wrist joints were within normal limit. Radiograph of right forearm revealed sclerosis of entire right ulna with dripping candle wax appearance with bowing deformity of ulna. She underwent osteoplasty of right ulna and biopsy. Oral bisphosphonate was started.

DISCUSSION

Due to the rarity of the condition, there is still no standard guideline of the treatment of Melorheostosis, the widely practiced mode of treatment is symptomatic with analgesics, contracture release and deformity correction in extreme cases. If the diagnosis is doubtful it is important to rule out other sinister causes such as infection and malignancy. Biopsy is indicated only to confirm diagnosis.

CONCLUSION

Early diagnosis of Melorheostosis still remains challenge due to paucity of the condition. Melorheostosis should be included in one of the differential diagnosis of any hypersclerotic conditions of bone.

Surgical treatment of progressive melorheostosis worsening over 19 years: A case report

BACKGROUND

Melorheostosis is a relatively rare disease, which may cause chronic pain, soft tissue mass and restricted range of motion. Diagnosis and treatment of melorheostosis remains challenging.

CASE REPORT

We describe a patient with sclerotic bone involving the left acetabulum, femur, tibia, and talus. Over 19 years this patient showed slow progression of disease. The bone mass in the right popliteal region resulted in limitation of knee motion. Comprehensive management including physical therapy, medications and surgeries were adopted to obtain a full range of motion and no recurrence for 2 years.

DISCUSSION

Accurate diagnosis and adequate treatments are critical to melorheostosis patients. Resection of redundant calcified mass is an effective method to treat severe limitation of range of motion associated with knee melorheostosis.

Clinical report of metacarpal melorheostosis: a rare disease with "the dripping candle wax" appearance on different imaging modalities

Melorheostosis is a rare benign bone dysplasia characterized by dysostosis and sclerosis. The classic "dripping candle wax" appearance on imaging is a typical finding for the diagnosis. The authors report the case of a patient presenting with a hard and painful mass on the dorsal side of the hand.

Aneurysmal bone cyst-like changes developed in melorheostosis with epiphyseal osteopoikilosis

Aneurysmal bone cyst (ABC) is a rare and usually painful condition, representing about 1% of all bone tumors. A geographical lytic, expansile, and septated radiological pattern, with fluid-fluid levels on MRI, is classically displayed. ABC can be a primary bone lesion (70% of patients) or can arise in an underlying condition and is subsequently named "ABC-like changes" (30%). ABC-like changes are more frequently encountered in skeletal segments affected by chondroblastoma, fibrous dysplasia, giant cell tumor, osteoblastoma, non-ossifying fibroma, and osteosarcoma. In this article, we describe the first case of ABC-like changes developed in association with an ultra-rare sclerosing bone disease: melorheostosis. Melorheostosis is characterized by recognizable patterns on radiological studies with a pathological increased bone density and a cortical thickening within the periosteal or endosteal space, usually with a "dripping candle wax" appearance. More rarely, other different radiological patterns can be observed, such as "osteopatia striata-like," "osteoma-like," "myositis ossificans-like," and mixed patterns. Pain and limb hypotrophy are the most common clinical manifestations. We report the case of a Caucasian male with a clinic-radiological diagnosis of melorheostosis (with epiphyseal osteopoikilosis) since the age of twelve. At the age of nineteen, he suffered from increased pain in the proximal right thigh, and the radiological control revealed an expansive septated lesion at the right proximal femoral bone. The diagnosis of ABC-like changes developed in melorheostosis was obtained after CT-guided bone biopsy and confirmed by open-incisional biopsy.

A focus on melorheostosis disease: a literature review and case report of femoral-acetabular impingement due to melorheostosis treated with surgical hip osteoplasty

OBJECTIVE

Melorheostosis is a rare, non-hereditary, benign bone disease characterized by abnormal bone growth. Generally, melorheostosis develops during childhood or adolescence and progresses gradually over time. This disease represents a true challenge to the physician because of its variability due to location, extension of the affected bone, and involvement of associated soft tissue. Pain management, physical therapy, and surgery may be recommended, depending on the individual case. This review aims to get an overview of the latest evidence relating to epidemiology, clinical and radiographic characteristics, diagnosis, and possible therapeutic strategies for melorheostosis and describe our experience through a clinical case.

METHODS

We designed a comprehensive literature search on melorheostosis in MEDLINE (via Pubmed) up to April 2023 and reviewed reports published in international journals.

RESULTS

The purpose is to highlight the importance of a multidisciplinary approach in the management of a rare disease such as melorheostosis. We discuss the role of different physicians, including genetists, rheumatologists, physiatrists, physical therapists, and orthopedic surgeons, in providing accurate diagnoses and effective treatments. We conducted a comprehensive review of the literature on the treatment of melorheostosis to support these findings. In addition, the article presents a case study of a patient suffering from melorheostosis, focusing on difficulties in reaching a correct diagnosis and attempts towards conservative and surgical interventions. The patient underwent hip arthroplasty, and the final result was an improvement in function and a reduction in pain.

CONCLUSIONS

Managing melorheostosis can be challenging, and there is no standardized treatment for this condition at the moment.

A case of secondary hypertrophic osteoarthropathy from medieval Tuscany (central Italy, 10th-12th centuries CE)

OBJECTIVES

This study aims to provide a detailed evaluation of a case of secondary hypertrophic osteoarthropathy (HOA) and to explore insights into the presence and consequences of disease in medieval rural Italy.

MATERIALS

The skeleton of a male (US 4405) with an estimated age at death of 51-69 years excavated from the medieval rural site of Pieve di Pava (Siena, Italy).

METHODS

Macroscopic and radiological (x-ray, CT) analyses were performed.

RESULTS

Symmetrical extensive periosteal new bone formation on the diaphyseal and metaphyseal regions of this individual's long bones; the lower limbs were more extensively and severely affected than the upper limbs and the distal segments were more severely altered in comparison to the proximal ones.

CONCLUSIONS

The macroscopic and radiological features are highly consistent with a diagnosis of secondary HOA.

SIGNIFICANCE

The excellent state of preservation allowed the evaluation of rarely noted skeletal manifestations of HOA and provided insight into aspects of rural life in medieval Italy.

LIMITATIONS

Molecular analysis was not successful in sequencing the aDNA of tuberculosis, therefore the underlying primary cause of secondary HOA, whether pulmonary or extrapulmonary, remains obscure in this case.

SUGGESTION FOR THE FUTURE RESEARCH

It is advisable to regularly revisit the data available from osteoarchaeological collections in order to identify further cases of HOA, along with to further investigate the known cases to search for the underlying primary disease.

Pachydermoperiostosis: a case report of initial improvement with etoricoxib

Introduction and importance

Pachydermoperiostosis (PDP) is a syndrome characterised by the triad of pachydermia, digital clubbing and periostosis of long bones and its scarce incidence and similarity in clinical features with acromegaly makes the diagnosis challenging. The elevated PGE2 levels have been hypothesised as one of its mechanisms and therapies have been targeted to inhibit this prostaglandin.

Case presentation

A 25-year-old man with no comorbidities presented to OPD with a 10-year history of bilateral pain and swelling of the hands and feets associated with hyperhidrosis, grade IV clubbing and marked skin thickening on his forehead. X-rays revealed hyperostosis of the metacarpals, proximal and middle phalanges and periosteal bone formation with cortical thickening of the ankle joint. Tests done to rule out differentials such as thyroid acropachy, acromegaly, psoriatic arthritis were normal and a clinical diagnosis of PDP, a rare genetic disease characterised by pachyderma, digital clubbing and periostosis was made.

Clinical discussion

The patient was managed conservatively with etoricoxib for 6 months on a follow-up basis. The symptoms were improving and a repeat X-ray showed partial improvement of soft tissue thickening and periostosis.

Conclusion

PDP is a rare diagnosis with no clear consensus on a management approach. Its management with selective COX-2 inhibitors such as etoricoxib should be considered but its long-term effects should be studied further.

Melorheostosis: A Review of the Literature and a Case Report

Background and Objectives: Melorheostosis, also referred to in the literature as Leri's disease, is an unusual mesenchymal dysplasia with the clinical appearance of benign sclerosing bone dysplasia; it frequently occurs in late adolescence. Any bone in the skeletal system can be affected by this disease, though the long bones of the lower extremities are the most common, at any age. Melorheostosis has a chronic evolution, and symptoms are usually absent in the early stages. The etiopathogenesis is still unknown, however, numerous theories have been proposed that could explain the appearance of this lesion formation. An association with other benign or malignant bone lesions is also possible, and associations with osteosarcoma, malignant fibrous histiocytoma, or Buschke-Ollendorff syndrome have also been reported. There have also been reported cases of the malignant transformation of a pre-existing melorheostosis lesion into malignant fibrous histiocytoma or osteosarcoma. The diagnosis of melorheostosis can be made only based on radiological images, but, due to its polymorphism, additional imaging investigations are often necessary and sometimes only a biopsy can establish a definite diagnosis. Because there are currently no guidelines for treatment based on scientific evidence, due to the low number of cases diagnosed worldwide, our objective was to highlight the early recognition and specific surgical treatments for better prognosis and outcomes. Materials and Methods: We conducted a review of the literature consisting of original papers, case reports, and case series and presented the clinical and paraclinical characteristics of melorheostosis. We aimed to synthesize the treatment methods available in the literature as well as determine possible future directions related to the treatment of melorheostosis. Furthermore, we presented the results of a case of femoral melorheostosis admitted to the orthopedics department of the University Emergency Hospital of Bucharest in a 46-year-old female patient with severe pain in the left thigh and limitation of joint mobility. Following the clinical examination, the patient complained of pain in the middle third of the left thigh in the antero-medial compartment; the pain appeared spontaneously and was aggravated during physical activity. The pain started about two years prior, but the patient experienced complete pain relief after the administration of non-steroidal anti-inflammatory drugs. In the last six months, the patient presented an increase in pain intensity without significant improvement following the administration of non-steroidal anti-inflammatory drugs. The patient's symptoms were mainly determined by the increase in the volume of the tumor and the mass effect on the adjacent tissues, especially on the vessels and the femoral nerve. The CT examination and bone scintigraphy showed a unique lesion in the middle third of the left femur and no oncological changes in the thoracic, abdominal, and pelvic regions; however, at the level of the femoral shaft, there was a localized cortical and pericortical bone lesion formation that surrounded approximately 180 degrees of the femoral shaft (anterior, medial, and lateral). It had a predominantly sclerotic structure but was associated with lytic areas with thickening of the bone cortex and areas of periosteal reaction. The next therapeutic gesture was to perform an incisional biopsy using a lateral approach at the level of the thigh. The histopathological result supported the diagnosis of melorheostosis. Additionally, immunohistochemical tests completed the data obtained after the microscopic examination through the classic histopathological technique The patient was discharged and included in a full medical recovery program for eight weeks in a specialized medical center, during which she also received analgesic treatment in maximum doses, but without improvement regarding her symptoms. Taking into account the chronic evolution of the pain, the complete lack of response to conservative treatment after eight weeks, and the lack of treatment guidelines in the case of melorheostosis, a surgical approach needed to be considered. The surgical option in this case, considering the circumferential location of the lesion at the level of the femoral diaphysis, was a radical resection. The surgical approach consisted of segmental resection to healthy bone tissue and reconstruction of the remaining defect with a modular tumoral prosthesis. At the 45-day postoperative control, the patient no longer complained of pain in the operated-on limb and was mobile with full support without gait difficulties. The follow-up period was one year, and the patient presented complete pain relief and a very good functional outcome. Results: In the case of asymptomatic patients, conservative treatment seems to be a good option with optimal results. However, for benign tumors, it remains unclear whether radical surgery is a viable option. Conclusions: Melorheostosis remains an incompletely understood disease, given the limited number of cases worldwide, and thus, there is a lack of clinical guidelines regarding specialized treatment.

Benign incidental do-not-touch bone lesions

Benign bone lesions may occasionally be incidentally detected on radiographs and are also increasingly found on CT or MRI performed for other clinical indications. Although mostly asymptomatic or associated with minor symptoms, these lesions may simulate true pathological lesions, causing problems in diagnosis. For instance, asymptomatic benign bone lesions can be misinterpreted as metastasis when incidentally encountered in a patient with known cancer. Recognising these entities as "do-not-touch" lesions helps avoid unnecessary further investigation or harmful intervention. In this review, we highlight three groups of bone incidentalomas found in adults, namely: osteolytic lesions, osteoblastic lesions, and bone protuberances. We aim to review the key imaging features of selected common and less common conditions in these three groups, so as to help radiologists confidently identify these benign do-not-touch lesions and to distinguish them from more sinister pathological lesions.

Late-Onset Melorheostosis: A Case Report

Melorheostosis is a rare benign bone pathology involving bone dysplasia and hyperostosis. The disease can be recognized with a characteristic radiographic feature of radiopaque lesions dripping along a long bone's diaphysis. The aberrant bone formation and development manifests mainly as pain, edema, and paresthesia of the affected limb. Severe cases may report limb deformity as well as limited range of motion. Until now, there have been approximately 300 cases reported about melorheostosis worldwide and its diverse clinical picture and age distribution. In Vietnam, there is only one known case of melorheostosis discovered incidentally via radiography. The scarcity of cases presents a challenge within the medical community in recognizing and diagnosing the condition, and a delayed diagnosis can lead to severe contracture and compromised limb motility. In this article, we reported an 82-year-old case of polyostotic melorheostosis with late onset and predominant edema, affecting the sternum, the ribs, and multiple bones of the right extremities and presented our clinical approach for a geriatric patient with chronic limb edema. Our case is distinctive in terms of anatomical location as well as the predominant 20-year non-pitting edema. A prompt diagnosis was made upon the classic dripping candle wax radiographic features emphasizing the role of plain X-ray in establishing the diagnosis without extraneous utilization of other modalities and invasive procedures. Exclusion of other causes of chronic edema such as lymphadenopathy, malignancy as well as parasitic infection is of clinical importance.

Disorganization and Musculoskeletal Diseases: Novel Insights into the Enigma of Unexplained Bone Abnormalities and Fragility Fractures

PURPOSE OF REVIEW

Describe the potential contribution of disorganized tissue to the pathogenesis of bone abnormalities and fractures. Especially, fractures that are unexplained by bone loss (osteoporosis) or structural deterioration.

RECENT FINDINGS

Currently, bone fragility is primarily viewed as due to loss, or decay (osteoporosis). However, it is also acknowledged that this view is limited because it does not explain many fractures or abnormalities such as necrosis, sclerosis, or infarcts. Atypical femoral fractures (AFFs) during antiresorptive therapy are an example. Hence, it is proposed that another distinct mechanism is responsible for bone diseases. A remarkable bone property distinct from mass and decay is the organization (arrangement) of its components. Components must be perfectly assembled or well-stacked to ensure "the right amount of bone, at the right place". Disorganization is an aberration that is conspicuous in many diseases, more so in conditions poorly associated with bone mass and decay such as osteogenesis imperfecta, hypophosphatasia, and AFFs. However, despite the likely critical role of disorganization, this feature has received limited clinical attention. This review focuses on the potential contribution of disorganization to bone in health and diseases. Particularly, we propose that disorganization, by causing ineffective transfer of loads, may produce not only bone abnormalities (pain, necrosis, infarct, sclerosis, delayed healing) but also fractures, especially AFFs or stress fractures. A disorganized element is one that is where it shouldn't be (improperly stacked elements). Hence, disorganization can be measured by quantifying the extent to which a tissue (pixel within an image) is at an incorrect location.

Hereditary Metabolic Bone Diseases: A Review of Pathogenesis, Diagnosis and Management

Hereditary metabolic bone diseases are characterized by genetic abnormalities in skeletal homeostasis and encompass one of the most diverse groups among rare diseases. In this review, we examine 25 selected hereditary metabolic bone diseases and recognized genetic variations of 78 genes that represent each of the three groups, including sclerosing bone disorders, disorders of defective bone mineralization and disorder of bone matrix and cartilage formation. We also review pathophysiology, manifestation and treatment for each disease. Advances in molecular genetics and basic sciences has led to accurate genetic diagnosis and novel effective therapeutic strategies for some diseases. For other diseases, the genetic basis and pathophysiology remain unclear. Further researches are therefore crucial to innovate ways to overcome diagnostic challenges and develop effective treatment options for these orphan diseases.

A case of spinal melorheostosis

Melorheostosis is a rare bone dysplasia of unknown etiology with an incidence of 0.9 cases per million. It typically affects the upper or lower limbs and can cause severe deformity and functional impairment. Diagnosis is radiological and is often described as a “flowing candle wax” appearance on the radiograph. Treatment is individualized depending on the site and severity of symptoms. We report a rare case of spinal melorheostosis. We demonstrate the imaging features of melorheostosis on CT and MRI. We discuss the classification, genetics, and management of this condition.

Challenge in Diagnosing Osteopoikilosis: A Case Report

Background: Osteopoikilosis is a rare benign osteosclerotic dysplasia and occurs in 1/50,000 people. Osteopoikilosis is inherited in an autosomal dominant and associated with several clinical manifestations. Currently, there is no agreement on diagnosing osteopoikilosis.  In this case report, we describe a 24-year-old female patient complaining of a lump and pain in the sole of the right foot.  Case presentation: A 24 years female complained of a painful lump on the right pedis for one year. On physical examination of the right foot found a painful lump with firm boundaries, no sign of inflammation or trauma, and 1 cm x 0,5 cm x 0,5 cm in size. We perform a radiographic examination including bone survey and found multiple homogenous sclerotic lesions were spread over almost all visualized bony structures with oval to round in shape, varied in size, and well-defined borders. The laboratory examination shows normal results. Based on the findings described above, we diagnosed the patient with osteopoikilosis. The patient was provided with analgesics as therapy and periodic observation. Conclusion: Osteopoikilosis is a rare case and is generally found incidentally on radiographic examination. The combination of history taking, clinical manifestations, and typical radiographic findings is sufficient to establish the diagnosis. This can prevent unnecessary examinations or invasive procedures. Keywords: Osteopoikilosis, diagnosis, rare bone disease

Case report of Osteopoikilosis in patient with psoriatic arthritis

Osteopoikilosis (OPK) is one of the rare genetic musculoskeletal, non-inflammatory disorders that we should increase awareness toward. We report a case of a patient diagnosed with psoriatic arthritis with incidental imaging findings of lesions suggestive of osteopoikilosis.

[Sclerosing hyperostotic bone disorders]

CLINICAL/METHODICAL ISSUE

Diagnosis of sclerosing and hyperostotic bone disorders (SHS) is challenging. The correct and early identification of SHS can have therapeutic, prognostic and, in case of genetic SHS with regard to the risk of inheritance, advisory consequences.

STANDARD RADIOLOGICAL METHODS

For diagnosis, radiographic examinations and supplementary computed tomography (CT) and magnetic resonance imaging (MRI) are used. These are of indicative nature. Definitive diagnosis is usually made by genetic differentiation.

METHODICAL INNOVATIONS

In combination with the age of the affected person and the location of the osseous changes the characteristic image criteria are important. These are summarized in groups in this overview.

PRACTICAL RECOMMENDATIONS

Projection radiography in two planes is the imaging modality of choice. CT and MR can detect additional differential diagnostic criteria and should be indicated when needed.

Sclerotic bone lesions caused by non-infectious and non-neoplastic diseases: a review of the imaging and clinicopathologic findings

Bone sclerosis is a focal, multifocal, or diffuse increase in the density of the bone matrix on radiographs or computed tomography (CT) imaging. This radiological finding can be caused by a broad spectrum of diseases, such as congenital and developmental disorders, depositional disorders, and metabolic diseases. The differential diagnosis can be effectively narrowed by an astute radiologist in the light of the clinical picture and typical findings on imaging. Some of these lesions are rare and have been described as case reports and series in the literature. This article aims to collate the clinical-radiologic findings of non-infectious and non-neoplastic causes of bone sclerosis with relevant imaging illustrations.

Melorheostosis of the Fossa Intercondylaris Femoris - A Case Report and Review of the Literature

Introduction:

Melorheostosis is a rare benign bone condition characterized by excessive segmental sclerosis of cortical bone being reminiscent of dripping candle wax. It typically affects the long bones and can cause impingement and nerve compression syndromes that may require surgical treatment.

Case Report:

We report the case of a 49-year-old male patient with a 12-month history of the left-sided knee pain and a concomitant limitation of his left knee flexion to 90 degree. Radiographic and magnetic resonance imaging revealed the typical radiographic appearance of melorheostosis with an extraosseous lesion in the fossa intercondylaris femoris being causative for the limited knee range of motion. Following the resection of the extraosseous part of the lesion through a direct open approach, the patient is pain free with a maximum of 110 degree knee flexion at 12-month follow-up.

Conclusion:

Melorheostosis can present with manifold clinical manifestations that potentially require surgical treatment. Even in patients with a challenging localization of extraosseous lesions, a good to excellent functional outcome is possible.

Cross-Sectional Imaging Useful in Melorheostosis

Melorheostosis is a rare disease of bone overgrowth that is primarily diagnosed based on imaging studies. Recently, the association of different radiological patterns of the disease with distinct genetic cause was reported. Several case reports have described the radiological findings in patients with melorheostosis. However, the added value of cross‐sectional imaging with CT and MRI beyond X‐rays has not been investigated. The aim of the current study was to investigate this existing gap in knowledge. Forty patients with melorheostosis seen at the National Institute of Health Clinical Center were included in the study, and all their imaging studies were analyzed. The sequence of interpretation was X‐ray followed by CT and then MRI. CT images were extracted from whole‐body 18F‐sodium fluoride positron emission tomography/CT studies. The information from CT reclassified the initial X‐rays based radiological pattern in 13 patients. Additionally, CT comprehensively identified joint involvement and disease extent. In 76% of patients (n = 29) who underwent MRI, additional findings were noted, ranging from soft tissue edema to identification of soft tissue masses and incidental findings. MRI did not provide additional information on skeletal lesions beyond CT scans. However, it revealed the extension of soft tissue ossification into ischiofemoral space in four patients who complained of deep gluteal pain consistent with ischiofemoral impingement syndrome. In addition, MRI revealed soft tissue edema in 20 patients, 9 of whom had bone marrow edema and periosteal edema in the tibias consistent with shin splints. These findings suggest that select patients with melorheostosis should be evaluated with both CT and MRI, particularly patients in whom the distribution of pain does not correlate with the anatomic location of the disease in plain radiographs. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Axial melorheostosis: A rare presentation

Melorheostosis is a rare sclerosing bone dysplasia that most commonly affects the lower extremity long bones in a sclerotomal distribution. Melorheostosis of the spine is a particularly rare manifestation of this disease. In the appendicular skeleton, melorheostosis has a pathognomonic imaging appearance of flowing hyperostosis resembling melted candle wax flowing down the margins of a candlestick. In the spine, it can have a variety of imaging manifestations from unilateral focal sclerotic lesions resembling enostoses, to more bulky and deformative hyperostosis that span and fuse multiple adjacent spinal segments. This combination of nonaggressive radiologic features makes melorheostosis a particularly important diagnosis for radiologists to understand so that they may spare their patients unnecessary biopsy. Here we present the clinical features and computed tomography findings in a 33-year-old male with spinal melorheostosis involving the first and second cervical vertebrae.

The dripping candle wax sign of melorheostosis

Melorheostosis is a rare benign bone disease including dysostosis and sclerosis. Dripping candle wax presence is a common and typical sign of melorheostosis. This sign appears as irregular hyperostosis of the cortical bone which is likened to melted wax flowing down one side of a candle. It can sometimes cause pain, stiffness joint, or limitation of motion in the affected areas implicitly but mostly has no symptoms. It is usually observed on plain radiography; its appearance is generally hyperplasia on one side of the bone. We report a 33-year-old male who has an incidental diagnosis of melorheostosis post-trauma.

A multi-omics approach expands the mutational spectrum of MAP2K1-related melorheostosis

Melorheostosis is a very rare sclerosing bone dysplasia characterized by asymmetrical and progressive cortical hyperostosis, usually with involvement of soft tissues surrounding the lesions. Recently Kang et al. identified somatic mosaicism for variants (p.Gln56Pro, p.Lys57Asn, or p.Lys57Glu) in the negative regulatory domain of MAP2K1, resulting in increased ERK1/2 signalling in affected tissues. In our study, we employed several sequencing technologies to unravel genetic variants (only present in affected tissues) from four sporadic melorheostosis patients. In the exome of two patients, we identified the same variants (p.K57N and p.K57E) as previously described by Kang et al. WGS and RNAseq analysis in a third patient demonstrated the presence of a novel variant (p.Cys121Ser) in the catalytic domain of MAP2K1. In addition, gene set enrichment analysis of the transcriptome data demonstrated upregulation of proliferative pathways. Interestingly, increased proliferation of MAP2K1 p.Lys57Asn-positive osteoblasts has been reported by Kang et al. The variants located in the hotspot region of the negative regulatory domain as well as this newly identified p.Cys121Ser variant have all been classified as MAP2K1 variants that can constitutively activate the downstream effector Erk. Finally, in a fourth patient with classical radiographic features of melorheostosis, no pathogenic variants could be identified in MAP2K1 or the other candidate genes for melorheostosis (SMAD3; LEMD3; KRAS). In conclusion, our study strongly suggests that not only somatic variants in the regulatory domain of MAP2K1 but also in the catalytic domain can cause melorheostosis. Our observations confirm that mutations in MAP2K1 are a major cause of melorheostosis and also suggest further locus heterogeneity for this disorder.

A Rare Case of Melorheostosis in the Hand of a Saudi Woman

Melorheostosis is a very rare bone dysplasia, especially in the hand. Most cases were diagnosed incidentally, with the lower limbs being the most affected. This is the first Saudi woman with hand melorheostosis. A 33-year-old Saudi female had mild to moderate right-hand pain that started six years ago. Hand examination showed a full range of motion and full hand grip, and there was no tenderness upon palpation. Plain X-ray, unenhanced CT scan, and MRI of the hand showed an appearance resembling dripping candle wax as melorheostosis. The bone scan showed a nonvascular and nonacute lesion. An unenhanced CT scan demonstrated cortical and endosteal hyperostosis involving the proximal, middle, and distal third and fourth phalanges. Multi-sequential MRI of the hand demonstrated cortical hyperostosis involving the ulnar and radial aspect of the right fourth proximal, middle, and distal phalanges. Features in the X-ray, CT scan, bone scan, and MRI confirmed a diagnosis of melorheostosis with associated flexor tenosynovitis.

Clinical Evaluation of Melorheostosis in the Context of a Natural History Clinical Study

Melorheostosis is a rare dysostosis involving cortical bone overgrowth that affects the appendicular skeleton. Patients present with pain, deformities, contractures, range of motion limitation(s), and limb swelling. It has been described in children as well as adults. We recently identified somatic mosaicism for gain-of-function mutations in MAP2K1 in patients with melorheostosis. Despite these advances in genetic understanding, there are no effective therapies or clinical guidelines to help clinicians and patients in disease management. In a study to better characterize the clinical and genetic aspects of the disease, we recruited 30 adults with a radiographic appearance of melorheostosis and corresponding increased uptake on ¹⁸F-NaF positron emission tomography (PET)/CT. Patients underwent physical exam, imaging studies, and laboratory assessment. All patients underwent nerve conduction studies and ultrasound imaging of the nerve in the anatomic distribution of melorheostosis. We found sensory deficits in approximately 77% of patients, with evidence of focal nerve entrapment in five patients. All patients reported pain; 53% of patients had changes in skin overlying the affected bone. No significant laboratory abnormalities were noted. Our findings suggest that patients with melorheostosis may benefit from a multidisciplinary team of dermatologists, neurologists, orthopedic surgeons, pain and palliative care specialists, and physical medicine and rehabilitation specialists. Future studies focused on disease management are needed. © 2019 The Authors. JBMR Plus Published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.