Introduction
Diabetic myonecrosis or diabetic muscle infarction, was first described by Angervall and Stener in 1965. It is a very rare, under-recognised complication of poorly controlled long-standing diabetes mellitus with associated complications like nephropathy, retinopathy and neuropathy.1,2 Fewer than 200 cases have been reported in literature.2
Case presentation
A 59-year-old male, with poorly controlled type 2 diabetes mellitus (T2DM) for the last ten years, and hypertension for five years, presented with three months’ history of insidious onset bilateral thigh pains. Intensity of pain gradually increased, making the patient bed-bound for ten days prior to presentation. He also had diabetic nephropathy for the previous year, bilateral diabetic retinopathy for four months, and diabetic mononeuropathy of the left ulnar nerve for one month. He had a history of similar pain in his right thigh three years before, which had improved gradually over two months with low-dose oral steroids and analgesics received elsewhere.
Examination revealed mild swelling all over both thighs, with overlying cutaneous erythema and tenderness of the thigh muscles. Muscle power at the hips and knees could not be assessed due to pain; however, it was normal at the lower legs, upper limbs and neck. The possibility of idiopathic inflammatory myositis (IIM) was considered in view of symmetrical myalgia and muscle tenderness of the proximal groups of lower limbs.
On evaluation, deep vein thrombosis (DVT) was ruled out. Creatine phosphokinase (CPK) was 354 IU/l (normal range is 20–200IU/l). MRI of the thighs, performed during a previous episode in 2015, showed increased bulk of the right vastus lateralis muscle with hyperintense signal on short tau inversion recovery (STIR) images (arrow in Figure 1a,1b) and hypointense signal on T1-weighted images. MRI of the thighs during the present episode demonstrated similar changes, but this time with symmetrical involvement of multiple muscle groups (hip adductors, abductors, quadriceps and hamstrings) (arrows in Figure 1c). Review of histopathology slides of muscle biopsy from the right vastus lateralis performed in 2015 (Figure 2), showed ischaemic necrosis of muscle fibres (arrows) with scattered lymphocytes (arrowheads). Antinuclear antibody and anticardiolipin antibodies were negative. Other laboratory data are summarised in Table 1. CPK during the previous episode was 308IU/l, with a normal range of 39–300IU/l.
Figure 1a MRI of the right thigh in 2015 showing increased bulk of the right vastus lateralis muscle with hyperintense signal on STIR image (arrow) in coronal plane
Figure 1b MRI of the thighs in 2015 showing increased bulk of the right vastus lateralis muscle with hyperintense signal on STIR image (arrow) in transverse plane
Figure 1c MRI of the thighs during present episode, showing increased bulk of the bilateral multiple muscles with hyperintense signal on STIR image (arrows) in coronal plane
Table 1 Laboratory data
|
White blood cell count (4000–11000 /mm3)
|
9700
|
|
Erythrocyte sedimentation rate (0–20 mm/hr)
|
63
|
|
Aspartate aminotransferase (7–40 IU/l)
|
27
|
|
Creatine phosphokinase (20–200 IU/l)
|
354
|
|
Lactate dehydrogenase (200–400 IU/l)
|
235
|
|
Serum creatinine (0.9–1.4 mg/dl)
|
3.0
|
|
Haemoglobin A1C (4–6 %)
|
8.6
|
|
24 hour urine proteins (< 0.15 grams/day)
|
3.7
|
Taking into consideration the following points: long-standing poorly controlled diabetes, concomitant presence of other microvascular complications of diabetes, past history of similar myalgia in the right thigh with myonecrosis on muscle histopathology, normal muscle power at the upper limbs and neck, absence of cutaneous and other manifestations of IIM, CPK being just above the normal upper limit, the absence of antinuclear antibodies and the poor general condition of the patient, muscle biopsy was deferred and a diagnosis of recurrent DMI was made. The hypertension was treated appropriately, blood glucose was controlled with insulin and bed rest was advised with DVT-prophylaxis measures. The patient also received opioid analgesics and aspirin. He had minimal pain relief during his hospital stay, but over the next two months the pain gradually decreased and he was able to ambulate with support. This clinical improvement without the use of any immunosuppressant strongly supported the diagnosis of DMI.
