A 27-year-old man presented with an 8-year history of chronic right gluteal and posterior thigh pain, worsened by sitting and unresponsive to conservative treatment. Imaging revealed widespread melorheostosis and osteopoikilosis of the right lower extremity, with 2 gluteal soft tissue masses compressing the sciatic nerve. The masses were excised using a dual surgical approach, achieving successful sciatic nerve decompression. Postoperatively, the patient regained normal sitting and sleeping tolerance, with complete pain relief maintained over a 15-month follow-up. Melorheostosis, a rare sclerosing bone disorder sometimes associated with osteopoikilosis, may require surgery when large lesions cause nerve compression.

Sclerosing bone dysplasias encompass abnormalities in bone density, divided into hereditary and nonhereditary forms. Primarily diagnosed through radiography, they are often incidental findings. Among the hereditary forms, the following stand out: osteopetrosis, osteopoikilosis, multiple diaphyseal sclerosis (ribbing disease), osteopathia striata, and Camurati-Engelmann disease. Among the nonhereditary forms, intramedullary osteosclerosis and melorheostosis present specific radiographic characteristics. The main differential diagnoses include osteoblastic metastases, tuberous sclerosis, and renal osteodystrophy, requiring careful differentiation because of their similarities. As displasias ósseas esclerosantes abrangem anormalidades na densidade óssea, divididas em hereditárias e não hereditárias. Diagnosticadas principalmente por radiografia, muitas vezes são achados incidentais. Entre as formas hereditárias destacam-se a osteopetrose, a osteopoiquilose, a esclerose diafisária múltipla, a osteopatia estriada e a doença de Camurati-Engelmann. Entre as formas não hereditárias, a osteosclerose intramedular e a melorreostose apresentam características radiográficas específicas. Diferenciais importantes incluem as metástases osteoblásticas, a esclerose tuberosa e a osteodistrofia renal, exigindo diferenciação cuidadosa em razão das suas semelhanças.

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.

Buschke-Ollendorff syndrome (BOS) is a rare, usually benign, autosomal dominant genetic disease affecting about 0.005% globally. BOS commonly manifests with asymptomatic connective tissue nevi, sometimes with sclerotic bone lesions like osteopoikilosis or melorheostosis. However, BOS may develop severe, symptomatic complications that require surgical intervention. Here we report a 9-year-8-month girl presenting with multiple nonpruritic, nonpainful skin plaques scattered around the trunk, buttocks, and bilateral legs. She had a history of right varus foot with inadequate plantar flexion. Upon visiting, obvious leg length discrepancy (LLD) was noted. Lesional biopsy revealed increased fibroblasts within dermal collagen bundles. Verhoeff-van Gieson stain revealed scattered foci of thickened elastic fibers between collagen fibers, especially in the mid-dermis. Radiographic examination of the lower extremities showed multiple small, round-to-oval shaped, radiopaque spots on the pelvic bones, femurs, tibiae, and both feet. Hyperostosis along the long axis with "dripping candle wax" appearance was characteristic of osteopoikilosis and melorheostosis. Genetic analysis showed heterozygous point mutation in exon 1 of LEMD3 gene (c.1323C>A, p.Y441X), confirming diagnosis of BOS. Sequential and epiphyseodesis were performed to correct LLD with a favorable outcome at 2-year follow-up. BOS associated with severe bone abnormalities is rare, but orthopedic surgical intervention can provide satisfactory outcome.

Osteopoikilosis (OPK) is an extremely rare benign condition with autosomal dominant inheritance characterized by sclerosing bony dysplasia with multiple benign enostoses. It is characterized by symmetrically distributed numerous, small, well-defined, homogenous circular or ovoid radiodensities clustered in epiphysis and metaphysis of long bones in periarticular region, and in some cases diffusely present throughout axial and appendicular skeleton. There is no age and sex predilection; age at the time of diagnosis ranges from 15 to 60 years. It is usually asymptomatic but rarely in 15-20% patients slight juxta-articular pain and joint effusions can be seen. These are incidental radiological findings in most of the cases, also sometimes confused as bony metastasis. There are no specific clinical features; histological features are similar to bony island and it may be associated with connective tissue disorders, synovial osteochondromatosis, and a rare bone condition melorheostosis. We present a case of OPK in a 32-year-old male with bilateral hip and shoulder pain, based on the available literature and focus on clinical significance, due to its mimicking capability of other more severe conditions such as bone metastases and an extremely uncommon cause of bone pain. OPK is an uncommon hereditary condition involving juxta-articular region of long bones with intricate etiopathogenesis, often discovered incidentally on radiographs. It is characterized by multiple, symmetrical ovoid radiodensities, and in most instances confused with osteoblastic metastasis. This concludes that OPK is a condition that should be kept in mind to avoid misdiagnosis, in particular osteoblastic metastasis and undue distress to both the patients and doctors.