DMI is an uncommon complication of long-standing uncontrolled diabetes of both type 1 and 2 . The pathogenesis is not clear. The most likely hypothesis is vascular diseases like arteriosclerosis and diabetic microangiopathy . Thigh muscles are the most commonly affected and reports of lower leg involvement are very rare . Upper extremity involvement has also been reported .
Clinical features usually consist of local swelling, limitation and pain on motion, tenderness, and a palpable painful mass, usually without fever and severe induration. Muscle enzymes are usually not elevated and an elevated ESR was seen in about 50%.
Diagnosis can be made combining clinical presentation and radiologic imaging. MRI is one of the best methods. Electromyography has been shown to help in some cases . Biopsy confirms the diagnosis in over 90% of cases , but since it has potential complications, it should be reserved for atypical cases were diagnosis is hard to make. The main reason why biopsies are not performed regularly is that those who have biopsies also have a longer course of pain and associated problems.
The most common differential diagnoses are deep venous thrombosis and pyomyositis, although soft-tissue abscess, necrotizing fasciitis, dermatomyositis, proliferative myositis, focal myositis, nodular myositis, primary lymphoma of muscle, benign tumors or sarcomas of the muscle, diabetic amyotrophy, osteomyelitis, exertional muscle rupture, and ruptured Baker’s cyst were also noted [8, 9].
Diabetic dermopathy, sometimes termed pigmented pretibial papules, or “diabetic skin spots,” begins as an erythematous area and evolves into an area of circular hyperpigmentation that is in patients with long-standing diabetes and no treatment is warranted .
In our patient the presentation was localized muscle involvement and skin lesions in an uncontrolled diabetic patient, which DMI along with diabetic dermopathy had been diagnosed. This was the first report of DMI and diabetic dermopathy together. As the rate of diabetes mellitus is rising, we might be seeing these patients more often and we should be concerned about them. Treatment is controversial, but trials of anti-platelets, anticoagulation, analgesics, off-loading, rehabilitation methods, and anti-depressants have been used. We recommend more thorough clinical trials to see if these treatment regimens significantly improve the outcome.
In conclusion DMI is an uncommon complication of long-standing uncontrolled diabetes presenting with swelling and severe pain usually in lower extremity and usually prompts an extensive diagnostic workup to find etiology of localized myositis which might be unnecessary if the physician has a high level of suspicion, and a T2-weighted MRI images can be a good diagnostic help.