多发性骨髓瘤是一种常见的浆细胞肿瘤，通常伴有溶骨灶的形成，而骨硬化性骨髓瘤是浆细胞恶液质的一种非常罕见的形式。当检测到骨硬化性骨髓瘤时，骨硬化灶通常是 POEMS 综合征的一部分。没有 POEMS 综合征其他表现的骨硬化性骨髓瘤是一个不寻常的发现。在一名 46 岁女性中，颞顶区的骨硬化变化导致该病变上的软组织硬结，因此启动了进一步的调查。随后的影像学研究显示颅骨中有多个骨硬化灶。血液蛋白检查显示 8 g/L IgG-lambda 单克隆免疫球蛋白（IgG1 亚类）。为了寻找骨硬化变化的原因，进行了 FDG-PET/CT，结果显示没有 FDG 积聚，即没有其他肿瘤（乳腺癌或胃癌）。低剂量CT显示骨结构不规则，但未见明显溶骨或骨硬化病灶。为了绘制骨硬化变化的程度，随后进行了 NaF-PET/CT 想象，结果显示了多个氟化物高积累的点。顶骨活检显示骨硬化，伴有少量克隆性浆细胞浸润。 Trepanobioptic 骨髓取样显示 8% 的骨髓中存在非典型浆细胞浸润。骨髓的流式细胞术检查显示 0.37% 的浆细胞，但主要 (91%) 是具有 lambda 表达的克隆。大脑 MRI 发现无症状的脑膜增厚。患者没有 POEMS 综合征的证据；因此，我们得出的结论是，具有临床意义的单克隆丙种球蛋白病伴骨硬化，以前被称为骨硬化性多发性骨髓瘤。具有骨硬化性骨骼变化的临床意义的单克隆丙种球蛋白病（MGCS），在 CT 上记录，多病灶伴有密集的骨新生，在 NaF-PET 上记录/CT 没有 POEMS 综合征的证据，是一种极其罕见的浆细胞恶液质。本出版物记录了 IgG-lambda 型浆细胞增殖的独特临床表现，而没有 POEMS 综合征的迹象，以及 NaF-PET/CT 成像的作用。与多发性骨髓瘤相比，将这种疾病分类为具有骨硬化表现的 MGSC 更符合该疾病的惰性性质，且预后明显更好。

Multiple myeloma is a common plasma cell neoplasia usually accompanied by the formation of osteolytic foci, whereas osteosclerotic myeloma is a very rare form of plasma cell dyscrasia. When osteosclerotic myeloma is detected, osteosclerotic foci are usually part of the POEMS syndrome. Osteosclerotic myeloma without other manifestations of the POEMS syndrome is an unusual finding.In a 46-year-old woman, osteosclerotic changes of the temporoparietal region caused soft tissue induration over this lesion, which initiated further investigation. Imaging studies subsequently showed multiple osteosclerotic foci in the skull. Examination of blood proteins revealed 8 g/L of IgG-lambda monoclonal immunoglobulin, subclass IgG1. In search of the cause of the osteosclerotic changes, FDG-PET/CT was performed, which revealed no FDG accumulation, i.e., no other tumor (breast or stomach cancer). Low-dose CT showed irregular bone structure, but not significant osteolytic or osteosclerotic foci. To map the extent of osteosclerotic changes, NaF-PET/CT imagination followed, which revealed multiple spots with high fluoride accumulation. A parietal bone biopsy showed osteosclerosis with minor clonal plasma cell infiltration. Trepanobioptic bone marrow sampling revealed an infiltration of bone marrow with atypical plasma cells in 8%. Flow-cytometric examination of bone marrow showed 0,37% of plasma cells, however predominantly (91%) clonal with lambda expression. MRI of the brain identified asymptomatic meningeal thickening. There was no evidence of POEMS syndrome in the patient; thus, we concluded the diagnosis as monoclonal gammopathy of clinical significance with osteosclerosis which was previously termed osteosclerotic multiple myeloma.Monoclonal gammopathy of clinical significance (MGCS) with osteosclerotic skeletal changes, documented on CT and multiple foci with intensive osteoneogenesis, documented on NaF-PET/CT without evidence of POEMS syndrome, is an extremely rare form of plasma cell dyscrasia. This publication documents the unique clinical manifestations of IgG-lambda type plasma cell proliferation without signs of POEMS syndrome and the role of NaF-PET/CT imaging. Classification of this disease as MGSC with osteosclerotic manifestations is more consistent with the indolent nature of the disease with a significantly better prognosis, compared with multiple myeloma.