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CASE REPORT
Year : 2022 | Volume
: 68
| Issue : 4 | Page : 236-238
Unusual magnetic resonance imaging findings of cystic bone lesions in congenital generalized lipodystrophy
TF T de Oliveira1, MR C Natal2, AA Teixeira2, BB Machado3
Correspondence Address:
B B Machado
Unimed Sul Capixaba Hospital, Cachoeiro de Itapemirim
Brazil
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/jpgm.jpgm_1031_21
Cystic bone lesions are the hallmark of skeletal abnormalities in patients with congenital generalized lipodystrophy (CGL). However, their pathophysiology is still unclear and theories about their origin remain largely speculative. This article reports on a patient with CGL and cystic bone lesions, some of them with unusual magnetic resonance imaging (MRI) findings that include elevated signal intensity on T1-weighted images and fluid–fluid levels, the latter evolving to a more “classic” cystic appearance on follow-up. Even though similar findings were first described almost 30 years ago, little attention was given to them back then; furthermore, other than the present report, no other study has performed sequential exams to follow their evolution in serial MRI. The authors conduct a review of the literature, hypothesizing that these remarkable findings may reflect an intermediate stage in the process of cystification of the abnormal bone marrow, incapable to perform adipose conversion, lending factual support to the modern theories about this issue.
Keywords: Berardinelli-Seip syndrome, bone cysts, congenital generalized lipodystrophy, fluid levels, magnetic resonance imaging
Even though cystic-appearing bone lesions are considered a classic finding and part of the spectrum of manifestation of congenital generalized lipodystrophy (CGL),[1] there is a paucity of articles addressing their appearance on imaging and little is known about their natural evolution. In this article, the authors report on a case of a patient with CGL and large cystic bone lesions on magnetic resonance imaging (MRI) presenting high signal intensity on T1-weighted images and fluid–fluid levels, the latter showing progression to a more “typical” cystic appearance on follow-up. These unusual findings are compatible with an intermediate stage in the process of cystification of the abnormal bone marrow.
:: Case ReportA 21-year-old male with CGL diagnosed in early infancy was referred for an MRI of the right arm to re-evaluate a fracture that occurred 9 years earlier. Skeletal radiographs performed back then revealed extensive cystic lucent lesions in the long bones, which were considered typical of his disease and remained essentially unchanged on serial studies [Figure 1]. A previous computed tomography (CT) scan had revealed sclerosis of the medullary bone of the vertebrae, ribs, scapulae, and of the segments of the long bones not affected by the aforementioned cystic lesions. On physical examination, the patient presented a muscular appearance, with nearly absent subcutaneous tissue.
Figure 1: Coronal T1-WI (left) and STIR (right) images. Two cystic lesions occupy most of the humerus: the biggest one occupies the diaphysis and distal epiphysis (asterisks) and the second one occupies the humeral head (stars). Hypointense bone marrow (squares) is interposed betweenThe most prominent MRI feature was the presence of fluid-filled lesions throughout the whole left humerus, with distinct signal intensity in the lesions of the humeral head and in the diaphysis and distal epiphysis. In the latter two, the fluid filling the large diaphyseal–epiphyseal cystic space was homogeneous, with intermediate to high signal intensity on T1-weighted images (T1-WI), higher than that of the skeletal muscles, and high signal intensity on short TI inversion recovery (STIR) [Figure 1]. On the other hand, the cystic lesion in the humeral head displayed internal bony septa and heterogeneous signal intensity, with fluid–fluid levels characterized by a supernatant presenting high signal on T1-WI (higher than that of the diaphyseal–epiphyseal lesion) and STIR (hypointense when compared to the diaphyseal–epiphyseal lesion), while the dependent portion displayed intermediate to low signal intensity in all sequences [Figure 2]. A small loculus in the humeral head contained fluid with signal intensity similar to that of the diaphyseal–epiphyseal lesion. The bone marrow was hypointense in all sequences in all bones included in the field of view. There was no abnormal post-gadolinium enhancement. Whole body MRI was also performed, showing cystic bone lesions and low signal intensity of the bone marrow throughout the body.
Figure 2: T1-WI (left) and STIR images (right), sagittal (a) and axial (b). There are fluid levels with a hyperintense supernatant (asterisks) and a dependent portion with intermediate to low signal (stars). A small cavity is seen posteriorly (squares), filled by fluidAn MRI performed 22 months later [Figure 3] showed disappearance of the fluid–fluid levels in the cystic lesion of the humeral head, which became partially filled with a heterogeneous and predominantly hypointense tissue growing from the periphery of the cavities, interpreted as fibrous in nature; the fluid filling these cavities was predominantly isointense when compared to that of the diaphyseal–epiphyseal lesion, which presented the same MRI features seen in the first study.
Figure 3: Follow-up MRI, T1-WI (left) and STIR (right) in the sagittal (a) and axial (b) planes. There is absence of the fluid levels previously seen in the epiphyseal lesion. The fluid filling the lesion is predominantly isointense :: Discussion The term lipodystrophy refers to a group of rare syndromes characterized by generalized or partial absence of adipose tissue, of which CGL (or Berardinelli-Seip syndrome) is the most common form.[2] The most striking feature in CGL is near-absence of all body adipose tissue.[1],[3],[4] Metabolic abnormalities and end-organ complications are also part of this syndrome, notably insulin-resistance leading to poorly controlled diabetes.[4]
The hallmark of CGL in the skeleton is the presence of osteolytic cystic lesions predominantly located in the long tubular bones and in the carpal, tarsal, and phalangeal bones. Their pathophysiology remains poorly understood, but it is currently believed that their development is related to failure in developing marrow adipose tissue and defective conversion of red to yellow marrow during childhood and adolescence; therefore, cyst formation at this time would represent a local reaction to the failed marrow adipose conversion.[5],[6]
Bone marrow in patients with CGL has been described to show intermediate to low signal intensity on T1-WI and diffuse high signal intensity (or fluid signal) on fluid-sensitive sequences, evocative of serous transformation.[6] As with cystic lesions, serous transformation of the bone marrow could result from unsuccessful formation and development of the normal adult fatty bone marrow and may represent a less advanced stage in patients undergoing osteolysis and frank marrow cystification.[3],[6],[7],[8] Serous transformation is known since long, initially described as catabolization of marrow fat in patients with severe starvation or cachexia but also described on MRI and on histopathological studies in several other pathologic conditions.[1]
Fluid levels within the cystic bone lesions in CGL were described only once.[3] Occasional hyperintense signal intensity on T1-WI was also reported.[1],[3] It is known that intraosseous lipomas frequently undergo fat necrosis and may also become predominantly/completely cystic; during this process the signal intensity of the necrotic areas on T1-WI is variable before complete cystic degeneration ensues and fluid levels may be present.[9],[10] It is licit to suppose that analog phenomena may occur during serous transformation/cystification of the marrow fat in patients with CGL, as intermediate stages probably occur before marrow liquefaction is complete. Although intracystic bleeding might cause fluid levels, isolated hemorrhage would not explain the ingrowth seen on follow-up, except if it was just part of a more elaborate process, as suggested in this article.
Even though fluid levels and high signal intensity on T1-WI within cystic bone lesions in patients with CGL were first described decades ago, these findings received little attention and were reported only once ever since. As cystic bone lesions usually do not demand MRI assessment, this may explain in part the scarcity of articles addressing their imaging appearance. Furthermore, CGL is exceedingly rare and under-recognized, so that it may take some luck to perform an MRI scan in a patient whose cystic transformation is yet underway. Based on the transformation of the imaging appearance seen on serial studies and relying on previously published data, the authors hypothesize that both findings – elevated signal intensity on T1-WI and fluid–fluid levels – represent intermediate stages in the process of cystification of a bone marrow devoid of fat and incapable to perform adipose conversion. To the best of the authors' knowledge, this is the first article to document these changes in serial MRI studies, lending factual support to the current theories about the origin of cystic bone lesions in patients with CGL.
Declaration of patient consent
The authors certify that appropriate patient consent was obtained.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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