A 59 year old male presented with gradually progressive severe pain in his left thigh with absence of constitutional symptoms. His past medical history was significant for poorly controlled type 2 diabetes mellitus managed with oral hypoglycemic agents for the past 2 years complicated by proliferative retinopathy, chronic kidney disease and erectile dysfunction.
Physical examination revealed a locally swollen, tender distal lateral left thigh and presence of bilateral pedal pulses. Left thigh movements were restricted in flexion, with no knee or hip joint effusion.
Investigations revealed an elevated CK 788 U/L (RR 1-185) and ESR 64mm/hr. A hemoglobin of 98 g/L. and a white cell count 7.3 × 109 /L. Vasculitic and autoimmune screen were negative. His renal function was stable with serum urea 22.2mmol/L (RR 3.6-8.4), creatinine 540umol/L (RR 60-120) and eGFR of 9mL/min. Liver function tests were normal. Glycemic control was poor with an HbA1c of 74mmol/mol (8.9%).
Ultrasound of the thigh revealed diffuse subcutaneous edema. MRI scan revealed extensive swelling and edema in the left vastus medialis, intermedius and lateralis muscles with sparing of rectus femoris, suggestive of myositis or myonecrosis
He was treated empirically with parenteral steroids with minimal response.
Subsequent muscle biopsy confirmed myofibre necrosis with regeneration of the quadriceps muscle. There was no evidence of vasculitis and blood vessels were normal.
There was significant improvement in muscle strength, swelling and function of the left thigh over the next few months. Repeat MRI 3 months later showed resolution of edema with minor residual signal changes in vastus lateralis and medialis.
This is a rare complication of poorly controlled diabetes and is usually associated with other microvascular complications. The exact pathogenesis remains unknown. It most commonly affects the quadriceps muscle, is self limited and is treated conservatively. The short term prognosis is good but long-term prognosis is poor with recurrence rates up to 47.2%.