Case 1405
Osteonecrosis in multiple symmetrical lipomatosis
Clinical History
Imaging Findings
On examination, there were large, bilateral, soft tissue masses extending from the neck to the upper back and shoulders (Fig. 1). The left ankle was red, hot and swollen. Ankle movements were painful.
Haematological and biochemical evaluation was unremarkable apart from mild renal impairment. A clinical diagnosis of cellulitis was made and a rapid recovery ensued after a course of antibiotics.
Plain radiographs of the left leg (Fig. 2) were taken to exclude osteomyelitis. Because of her appearances and the changes noted on plain radiography, MRI was performed for further evaluation. The patient was examined in a Siemens Magnetom 0.2 T open-core system. Images were obtained of both the neck (Fig. 3) and the legs (Fig. 4).
Discussion
MSL is rare in the UK and most prevalent in middle-aged Mediterranean males. The dominant clinical feature is painless fat accumulation around the neck, upper back and shoulders. Patients may become symptomatic due to compression of the great vessels and trachea and require surgery. Further manifestations include haematological, metabolic and hepatic disturbances and these are exacerbated by concomitant alcoholism.
Kazumi [2] described a mitochondrial defect leading to alteration of lipolysis in brown fat, the distribution of which is similar to the peculiar position of lipomas in MSL.
MRI [3] helps to determine the extent of the fat accumulation prior to possible surgical resection and also confirms the fatty nature of the subcutaneous masses. A liposarcoma may be identified by an alteration in the otherwise homogeneous MRI signal or by non-suppression in STIR sequences. Cushing's syndrome, which also shows excess fat deposition, is characterised by abnormal biochemisty and osteoporosis.
Osteonecrosis has not been described in MSL previously, however there are multiple associations of altered lipid metabolism and osteonecrosis. Bone infarctions are a recognised complication of hypercortisolism, pancreatitis, diabetes mellitus, alcoholism, and gout as well as haemoglobinopathies, collagen small vessel disease and Caisson disease [4].
Jones [5] examined the relationship of osteonecrosis with different clinical disorders characterised by defective lipid metabolism and suggested a common pathway of continuous or intermittent intraosseus fat emboli leading to focal intravascular coagulation and resulting in osteonecrosis.
Multiple symmetrical lipomatosis with extensive osteonecrosis has not been described previously and the present case might widen the differential diagnosis of bone infarction.
Final Diagnosis
References
-
[1]
-
[2]
-
[3]
-
[4]4. Resnick D, Sweet DE, Madewell JE. Osteonecrosis and Osteochondrosis. in: Resnick D. Bone and Joint Imaging 2nd ed., WB Saunders Co. 1996; 941-59.
-
[5]
