Introduction

DMI is an unusual condition that has been seen in patients with long-standing disease and poorly controlled diabetes mellitus. It is usually accompanied with nephropathy, neuropathy, and retinopathy and can be seen in both type I and type II diabetes mellitus. This condition was first described by Angervall and Stener in 1965 [1, 2]. It can be diagnosed by MRI or biopsy. Following resolution, the disease can reoccur [3]. We present the case of a 22-year-old woman who had 12-years history of type I diabetes mellitus.

Case description

A 22-year-old woman was admitted to the hospital due to pain in the left leg and difficulty in walking. The patient was diagnosed with type I diabetes mellitus (DM) 12 years ago. Her blood glucose levels were poorly regulated for the past 3 years. The patient described three previous episodes of extremity pain, which were improved by analgesics and rest. On admission, she could not walk without support, and heel strike was absent. On physical examination, her vital signs were normal. The anterior left leg was painful and firm on palpation; diffuse swelling extending to the knee and ankle with mild local fever and redness was present. The movements of the left knee and ankle were painful, and the range of motion was limited at the left knee and ankle. There was complete absence of active flexion in patient’s left big toe. Erythrocyte sedimentation rate (ESR) was 72 mm/h, creatine phosphokinase (CK) was normal, glucose was 295 mg/dl, and HbA1c was 9.8%. Glucose was (++++) in urine samples.

Sensory conduction velocities of superficial peroneal nerve and sural nerve and motor conduction velocity of bilaterally peroneal nerve and right tibial motor nerve were slightly slowed. Fibrillation potentials and positive sharp waves were detected in left tibialis anterior, vastus lateralis, and gastrocnemius muscles. In these muscles as well as in peroneus longus and extensor digitorum brevis, the amplitudes of motor unit action potentials (MUAP) were slightly reduced, the duration of MUAP were slightly shorter, and the ratio of polyphasic MUAP were increased. These electroneuromyographic findings revealed mild distal symmetrical sensory–motor polyneuropathy and myogenic involvement of the muscles of the left leg.

A magnetic resonance imaging (MRI) study of the left leg revealed abnormal diffuse signal changes (hyperintense in T2 series, isointense in T1 series) in left tibialis anterior, tibialis posterior, flexor digitorum longus, flexor hallucis longus, and soleus muscles. Mild fluid accumulation between the fascial planes around the triceps surae muscle was observed. (Fig. 1).

Fig. 1
figure 1

Increased signal changes at tibialis anterior, extensor digitorum longus, tibialis posterior, soleus muscles compatible with edema in axial sequences obtained from one-third of the leg are observed in T2-weighted MRG image

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Muscle biopsy from left gastrocnemius muscle revealed fiber size variability and scattered necrotic fibers along with regenerating fibers. There was no significant increase in fibers with internal nuclei. Inflammatory cells were present in the endomysium, but non-necrotic fiber invasion was not detected. Oxidative enzyme staining revealed intermyofibrillary irregularity in some of the muscle fibers. No pathological lipid or glycogen accumulation was detected. There was no significant increase in connective tissue. Vascular structures were normal. These findings were consistent with skeletal muscle microinfarcts associated with diabetes mellitus.

Treatment was planned as the regulation of blood glucose and analgesics, antiplatelet medication, bed rest, gentle stretching of the left knee and ankle, and transcutaneous electrical nerve stimulation. After 2 weeks, she was able to walk independently, but mild pain remained around the ankle. At follow-up, two recurrent episodes of diabetic muscle infarction, which had been aggravated by long walks, were observed. At the follow-up visit 6 months after the initial admission, firmness became more distinctive. An apparent firm mass in her left anterosuperomedial leg with severe atrophy and desquamation extending to the lower ankle was identified. A red demarcation line was separating atrophic area from the region around the mass (Fig. 2).

Fig. 2
figure 2

Left leg at 6-month follow-up. There was an apparent firm mass in her left anterosuperomedial leg, with severe atrophy and desquamation going through the lower ankle. A red demarcation line was separating these two sides

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Discussion

DMI is a rare condition that is usually seen in patients with long-standing disease and poorly controlled diabetes mellitus. It is usually accompanied with nephropathy, neuropathy, and retinopathy. It was first described by Angervall and Stener in 1965 [1]. DMI can be seen in both type I and type II diabetes mellitus [2]. Our patient had type I DM for 12 years, and she had mild neuropathy non-proliferative retinopathy and microalbuminuria.

DMI is usually seen in the lower extremity, but upper extremity involvement is also reported [4, 5]. Clinical features are local painful mass together with swelling and limited range of motion of the involved extremity. It begins with acute onset and persists for several weeks, and systemic signs of infection are absent. Localized tender area (90%), swelling, and indurations of the surrounding tissue are typical physical examination findings. Skin redness is not a common feature but was described in 5 cases by Morcuende. Also knee effusion was reported in 2 cases [6]. Our patient had diffuse swelling and sensitivity extending to the knee and ankle, which made us think of arthritis in differential diagnosis. At the first admission, our patient had mild skin rash, which became more remarkable at 6 months control (Fig. 2). Since rash is not a frequent finding of DMI, we needed to confirm diagnosis with biopsy.

The thigh muscle group is the most commonly affected side, and reports with lower leg involvement are not more than fifteen [1, 6–16]. Although there are cases with gastrocnemius and soleus muscle involvement [6–11], to our knowledge this is the second case with tibialis anterior muscle involvement [17]. Our case had elevated ESR, normal CK levels similarly with literature [2].

Patients with DMI are not usually diagnosed at first visit. Vessel pathologies (lower limb venous thrombophlebitis, arterial occlusion, vasculitis, compartment syndrome), joint pathologies (knee effusions, acute arthropathy), muscle disease (pyomyositis), and metastatic disease are sometimes reported as the first impression of the clinical picture [12, 16, 18]. The initial diagnosis for our patient was complex; we gave weight to amyotrophy, neuropathy, and arthropathy in differential diagnosis.

During diagnosis and differential diagnosis, MRI is used. Involved muscles are diffusely enlarged, borders look ill. Muscles show hyperintensity on T2-weighted images. T1-weighted images are isointense to hypointense. If there is hemorrhage within the infracted muscle, increased signal intensity on T1 can be observed. Varying degrees of edema in subcutaneous tissues and intermuscular fascia and subfascial fluid collection are reported. Best sequences to assess DMI are T2-weighted and STIR images. Contrast-enhanced techniques had been used. Diffuse enhancement of the muscle is expected. Necrotic portion of the affected muscle is observed as the lack of enhancement [19].

Differential diagnosis of DMI includes infections (pyomyositis, necrotizing fasciitis, cellulites, abscess, osteomyelitis), trauma (hematoma, exertional rupture of muscle, myositis ossificans), vascular (deep vein thrombosis, acute compartment syndrome), tumors (primary muscle lymphoma, soft tissue sarcoma, benign muscle tumor), inflammatory (focal inflammatory myositis, polymyositis, dermatomyositis), diabetes-related condition (diabetic amyotrophy), ruptured Baker’s cyst, adverse reaction of simvastatin, and arterial graft complication[20]. Muscle abscesses, focal myositis, nodular myositis, polymyositis, hemorrhage, or neoplasm is characterized by a mass lesion like DMI, while disruption of the normal muscle architecture on MRI is expected. Focal myositis is observed as an enhancing mass, which is not very painful. Necrotizing fasciitis cannot be differentiated by MRI only; it must be accompanied with fever, associated sepsis, cellulites, and elevated white blood cell count. Patients do not have severe pain like DMI, and multiple sites are not involved. Soft tissue tumors are not characterized with severe pain; they involve single or multiple muscles of the same compartment, but bilaterality and multiple, discontinuous muscle involvement are not seen. Osteomyelitis is excluded with the normal bone marrow signal and preserved cortical outline of the bone [13]. MRI findings of primary lymphoma of muscle are as follows: intermediate signal intensity on T1-weighted and T2-weighted images, involvement of more than one anatomical compartment, extension through subcutaneous area and along neurovascular bundle [21]. Patients do not have acute severe muscle pain in lower extremity, do not have DM, and do not recover spontaneously [15]. Sudden severe pain that was prominent in our patient, and MRI findings helped us to exclude all these conditions.

Post-traumatic sequel appears as hyperintense and heterogeneous signal changes in T1-weighted images.

Treatment of DMI is still controversial. Conservative management (bed rest, analgesics) medical therapy (antiplatelet drugs, anticoagulants, and/or steroids) was found to be more favorable than surgical treatment (excision of the infracted muscle), and non-surgical treatment was recommended [22]. Recovery time differs between the cases.

As a conclusion, DMI should be mentioned in rheumatology practice in patients presented with acute onset of extremity pain and swelling and who have poorly controlled diabetes mellitus. Treatment plan should include bed rest, analgesic and antiplatelet medications, regulation of blood glucose levels, and evaluation of end-organ complications. Patient education is of prime importance to prevent recurrences.