Pyomyositis
Pyomyositis
Pyomyositis is a primary bacterial infection of skeletal muscles presenting with minimal clinical symptoms during the early stages and affects immunocompetent and immunocompromised individuals. MRI is a sensitive and specific imaging modality for early detection. Here we report a young man with a recent history of type 2 diabetes and recovery from hepatitis E presenting with right thigh pain and minimal erythema diagnosed with right thigh pyomyositis with the assistance of an early MRI.
A 39-year-old man presented with a 5 day history of non-specific pain over the right thigh and a low grade fever. He was diagnosed with type 2 diabetes 3 months ago and had recovered from viral hepatitis E infection 4 weeks ago. Clinical examination revealed mild tenderness over the right thigh with normal overlying skin. Investigations revealed leucocytosis 18×10/l (reference range (RR) 4–12) with a normal creatine kinase (CK) value of 31·7 U/l (RR 24–195), HbA1c of 7·2% and a normal HIV antibody test.
The patient was advised admission to hospital and an MRI performed revealed the presence of high T2 signal changes within the quadriceps muscles which was suggestive of a possible diagnosis of pyomyositis (figure 1A, B). Although the right thigh was not massively swollen (figure 1C) surgical debridement revealed 1·5 l of pus (figure 1D) with ampicillin sensitive Staphylococcus aureus grown in culture. Intravenous antibiotics and insulin therapy resulted in complete recovery after 3 weeks with no residue or sequelae.
(Enlarge Image)
Figure 1.
(A) Coronal T1 weighted MRI images showing intermediate signal changes with a massively distended right quadriceps (arrow). (B) Axial T2 weighted MRI images showing hyperintense signals (arrow) in the right thigh suggestive of pyomyositis of the right thigh. (C) Pre-operative picture of both thighs showing lack of erythema of the right thigh. (D) Surgical drainage of the right thigh abscess revealing a high volume of purulent material after surgical incision and drainage. This figure is only reproduced in colour in the online version.
Pyomyositis is a bacterial infection of the skeletal muscle arising due to haematogenous spread rather than contiguous infection, which can lead to abscess formation and sepsis. The most commonly affected muscle groups are the quadriceps, gluteal and iliopsoas.Staphylococcus aureus is the causative organism in more than 75% of cases. Pyomyositis has three stages: the early stage 1 of the disease lasts between one to ten days and clinical presentation includes localised muscle ache, pain and low grade fever similar to our case. Apart from a woody feeling of the underlying musculature physical findings are minimal or absent. As the underlying muscle involvement is deep there is a lack of skin erythema and warmth. Pyomyositis is thus said to be missed during the early stages even by the most astute physicians. A delay in diagnosis could lead to sepsis and death. MRI is preferred as a diagnostic tool to make an early diagnosis. In stage 2 (purulent or suppurative) and stage 3 (sepsis) of the disease, clinical features are more apparent after 2–3 weeks from clinical onset. MRI features of pyomyositis in the early stages include an ill-defined muscle enlargement with hyper intense T2- weighted images. As in our case, fluid collection within the muscle is seen as hyper intense signals on T2-weighted images (figure 1B). A rim enhancement in the presence of uniform enhancement of muscles on T1-weighted post contrast images is suggestive of abscess formation. MRI also offers the additional advantage of assessing neighbouring structures including joints, bone and soft tissue.
Pyomyositis usually occurs in patients with longstanding or poorly controlled diabetes, recent viral infection but could also occur in immunocompetent individuals with a recent history of trauma. Laboratory tests show a normal CK despite muscle destruction. In our case pyomyositis was detected during the early stage and in the context of a recent history of diabetes and recovery from viral hepatitis E. Most patients recover completely with no sequelae after antibiotics and surgical drainage.
Although common in tropical countries this condition is now being increasingly reported in temperate climates too. Pyomyositis in our patient occurred after a short history of diabetes compared with long standing history of diabetes in previous reports. Interestingly, hepatitis A and C have been reported to occur prior to pyomyositis but not hepatitis E. This case highlights the importance of a high index of suspicion and early recognition of pyomyositis in patients with fever, thigh pain and minimal skin changes with pre-existing diabetes, viral infections or an immunocompromised state.
Pyomyositis is a primary bacterial infection of skeletal muscles presenting with minimal clinical symptoms during the early stages and affects immunocompetent and immunocompromised individuals. MRI is a sensitive and specific imaging modality for early detection. Here we report a young man with a recent history of type 2 diabetes and recovery from hepatitis E presenting with right thigh pain and minimal erythema diagnosed with right thigh pyomyositis with the assistance of an early MRI.
A 39-year-old man presented with a 5 day history of non-specific pain over the right thigh and a low grade fever. He was diagnosed with type 2 diabetes 3 months ago and had recovered from viral hepatitis E infection 4 weeks ago. Clinical examination revealed mild tenderness over the right thigh with normal overlying skin. Investigations revealed leucocytosis 18×10/l (reference range (RR) 4–12) with a normal creatine kinase (CK) value of 31·7 U/l (RR 24–195), HbA1c of 7·2% and a normal HIV antibody test.
The patient was advised admission to hospital and an MRI performed revealed the presence of high T2 signal changes within the quadriceps muscles which was suggestive of a possible diagnosis of pyomyositis (figure 1A, B). Although the right thigh was not massively swollen (figure 1C) surgical debridement revealed 1·5 l of pus (figure 1D) with ampicillin sensitive Staphylococcus aureus grown in culture. Intravenous antibiotics and insulin therapy resulted in complete recovery after 3 weeks with no residue or sequelae.
(Enlarge Image)
Figure 1.
(A) Coronal T1 weighted MRI images showing intermediate signal changes with a massively distended right quadriceps (arrow). (B) Axial T2 weighted MRI images showing hyperintense signals (arrow) in the right thigh suggestive of pyomyositis of the right thigh. (C) Pre-operative picture of both thighs showing lack of erythema of the right thigh. (D) Surgical drainage of the right thigh abscess revealing a high volume of purulent material after surgical incision and drainage. This figure is only reproduced in colour in the online version.
Pyomyositis is a bacterial infection of the skeletal muscle arising due to haematogenous spread rather than contiguous infection, which can lead to abscess formation and sepsis. The most commonly affected muscle groups are the quadriceps, gluteal and iliopsoas.Staphylococcus aureus is the causative organism in more than 75% of cases. Pyomyositis has three stages: the early stage 1 of the disease lasts between one to ten days and clinical presentation includes localised muscle ache, pain and low grade fever similar to our case. Apart from a woody feeling of the underlying musculature physical findings are minimal or absent. As the underlying muscle involvement is deep there is a lack of skin erythema and warmth. Pyomyositis is thus said to be missed during the early stages even by the most astute physicians. A delay in diagnosis could lead to sepsis and death. MRI is preferred as a diagnostic tool to make an early diagnosis. In stage 2 (purulent or suppurative) and stage 3 (sepsis) of the disease, clinical features are more apparent after 2–3 weeks from clinical onset. MRI features of pyomyositis in the early stages include an ill-defined muscle enlargement with hyper intense T2- weighted images. As in our case, fluid collection within the muscle is seen as hyper intense signals on T2-weighted images (figure 1B). A rim enhancement in the presence of uniform enhancement of muscles on T1-weighted post contrast images is suggestive of abscess formation. MRI also offers the additional advantage of assessing neighbouring structures including joints, bone and soft tissue.
Pyomyositis usually occurs in patients with longstanding or poorly controlled diabetes, recent viral infection but could also occur in immunocompetent individuals with a recent history of trauma. Laboratory tests show a normal CK despite muscle destruction. In our case pyomyositis was detected during the early stage and in the context of a recent history of diabetes and recovery from viral hepatitis E. Most patients recover completely with no sequelae after antibiotics and surgical drainage.
Although common in tropical countries this condition is now being increasingly reported in temperate climates too. Pyomyositis in our patient occurred after a short history of diabetes compared with long standing history of diabetes in previous reports. Interestingly, hepatitis A and C have been reported to occur prior to pyomyositis but not hepatitis E. This case highlights the importance of a high index of suspicion and early recognition of pyomyositis in patients with fever, thigh pain and minimal skin changes with pre-existing diabetes, viral infections or an immunocompromised state.
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