A rare case of osteomyelitis of the clavicle in a child due to Group A streptococcal infection

Abstract

Acute osteomyelitis of the clavicle is rare in the paediatric age group. We treated a 5-year-old boy who presented initially with fever and left shoulder pain, and subsequently developed swelling in the region of the left clavicle. Group A Streptococcus (GAS) was isolated in blood culture. MRI of the clavicle showed osteomyelitis of the medial clavicle. The child had incision and drainage of his clavicular collection. The child received intravenous benzylpenicillin and oral cephalexin in the initial presentation; he was treated with 2 weeks of intravenous ceftriaxone and 4 weeks of oral penicillin thereafter with the resolution of his symptoms. There are no previous case reports of osteomyelitis of the clavicle in children caused by GAS. This case highlights the importance of identifying the microbial aetiology in these children to ensure early initiation of treatment with appropriate antibiotics.

Background

Osteomyelitis of the clavicle is rare and may be difficult to diagnose in the paediatric age group. We present the case of a 5-year-old boy who presented with acute osteomyelitis of the clavicle caused by group A Streptococcus (GAS). To our knowledge, this is the first case report of osteomyelitis of the clavicle in children caused by GAS. This case highlights the importance of identifying the microbial aetiology in these children to help early initiation of treatment with appropriate antibiotics to ensure symptom resolution and good outcome.

Case presentation

A 5-year-old child was admitted with 5 days of fever, 3 days of blanching rash on his chest and back and 2 days of left shoulder pain and sore throat. The rash had resolved by the time of admission to the hospital.

There was no history of any recent trauma. He had a history of hot water spillage on his chest 3 years ago—he had healed burn scars on his chest. He was otherwise fit and well and was not on any medication. His immunizations were all up to date.

At presentation, he had a heart rate of 110 beats/min, respiratory rate of 24 breaths/min, a temperature of 39°C and blood pressure of 104/70 mm Hg. On examination, the child was unwell and in discomfort. Examination of his chest and abdomen was normal. Musculoskeletal examination showed restricted movements of his left shoulder mainly in abduction and external rotation. There was no localised swelling or tenderness in the region of the left shoulder; all other joint examination was normal. Skin examination was normal, and there was no erythema or localised warmth. Throat was mildly congested with no pus points or exudates noted. Ear examination was normal.

The child thereafter developed a swelling in the region of the left clavicle the next day, which was tender. Overlying skin examination demonstrated erythema with no local rise of temperature. He continued to have reduced movements of his left shoulder. Systemic examination was otherwise normal.

Blood tests showed a raised white cell count (WCC) of 14.9×10⁹/L and C reactive protein (CRP) of 211 mg/L (normal range: less than 5 mg/L). An X-ray of the left shoulder was done which was normal. An ultrasound of the chest wall was normal with no evidence of any abscess or collection—this included the evaluation of the left shoulder, clavicle and sternoclavicular joint and left chest wall.

The orthopaedic team reviewed the child, and septic arthritis was considered in the differential diagnosis during the initial presentation. An aspiration of the shoulder was not attempted during the initial admission due to associated overlying skin and soft tissue infection in the shoulder region and the risk of seeding the underlying joint with infection.

Blood culture demonstrated the growth of GAS (sensitive to penicillin and tetracycline) and coagulase-negative Staphylococcus (CONS) (this was considered a skin contaminant). Throat swab culture was negative—this was sent prior to starting antibiotics.

The child was initially started on intravenous ceftriaxone (1.6 g once a day) and flucloxacillin (1 g every 6 hours) for 2 days; this was changed to intravenous benzylpenicillin (1 g every 6 hours) following identification of GAS on blood culture. He had 5 further days of intravenous benzylpenicillin and was discharged home on 5 days of oral cephalexin (250 mg three times per day).

The child was afebrile after 3 days of intravenous antibiotics, the swelling in the region of left clavicle showed good improvement with the range of motion of the left shoulder normalising within 2 days. His repeat blood tests showed improvement with CRP of 138 mg/L and WCC of 10.2×10⁹/L.

The child developed a swelling in the region of the left clavicle on the last day of his oral cephalexin (12th day of antibiotics) with no history of fever or any associated symptoms. He was readmitted the next day to the hospital; examination showed swelling in the region of the left medial clavicle, which was erythematous and mildly tender (figures 1 and 2). There was a good range of motion in all joints including the left shoulder. Systemic examination was normal.

Figure 1.

Swelling in the region of the left clavicle (front view).

Figure 2.

Swelling in the region of the left clavicle (side view).

Investigations

Repeat blood tests including full blood count, renal and liver functions and CRP were normal. Repeat blood cultures were sterile. An echocardiogram was performed which was normal. MRI of the clavicle with contrast showed osteomyelitis of the medial clavicle with associated soft tissue phlegmon and subperiosteal collections (figure 3).

Figure 3.

MRI of the left shoulder and clavicle showing osteomyelitis of the clavicle.

Differential diagnosis

Differential diagnoses included trauma, cellulitis, soft tissue abscess, septic arthritis, osteomyelitis and malignancies including osteosarcoma and Ewing’s sarcoma.

Treatment

The child had an incision and drainage of the subperiosteal collections and soft tissue phlegmon. The underlying bone did not look diseased, and therefore no sections of the bone were removed.

Tissue culture was negative. Wound swab culture was also negative. The above cultures were most likely negative due to prior treatment with antibiotics.

A peripherally inserted central catheter was inserted, and the child was started on intravenous ceftriaxone (1.6 g once a day at 80 mg/kg/dose). As he remained clinically well and asymptomatic, he was continued on intravenous ceftriaxone for a total of 2 weeks (child went home between the doses of antibiotics). He was thereafter discharged home on 4 weeks of oral phenoxymethylpenicillin (125 mg four times per day).

Outcome and follow-up

The child had a total of 8 weeks of antibiotics and remained clinically well. He did not have any further symptoms and range of motion in all joints including the left shoulder remained normal.

The child was followed up by the orthopaedic team 2 months later and the paediatric team 3 months after discharge. The child continued to be well with no further recurrence of symptoms and was discharged from further follow-up.

Discussion

Osteomyelitis of the clavicle is a rare condition in the paediatric age group; it comprises less than 3% of all cases of paediatric osteomyelitis.^{1 2} This diagnosis can be easily missed because of its rarity, and delayed diagnosis has the potential to cause complications such as bony deformity and chronic osteomyelitis³ The most common bacterial aetiology in paediatric osteomyelitis is Staphylococcus aureus; other organisms that cause osteomyelitis in children include GAS, pneumococci, Kingella kingae and Gram-negative bacilli.^{4 5} However, there are no published case reports of GAS causing clavicular osteomyelitis in children.

The clavicle is the first bone that ossifies in fetal life,⁶ this is also a common bone to be fractured, up to 10%–15% of all fractures in children involve the clavicle.⁷ Non-traumatic aetiologies of clavicular swelling are rare,⁸ and can, therefore, cause diagnostic dilemma and delay in the initiation of specific management.

A systematic and methodical approach to infective clavicular lesions is therefore warranted. It is important to first exclude trauma or tumour as the cause of the clinical presentation. Once the above differential diagnoses are ruled out, the children should be started on broad-spectrum intravenous antibiotics. The antibiotic regimen should be modified based on blood cultures and surgical cultures. If blood cultures are negative, then the antibiotic regime should be tailored towards the most common causative pathogens⁹ after discussion with the microbiology and/or infectious disease teams.

In our child, we considered the differential diagnosis of fracture, soft tissue abscess, tumours, septic arthritis and osteomyelitis. There was no history of any trauma and no localised tenderness on palpation of the clavicle. We did not note any clinical features suggestive of tumours like bony tenderness or a palpable mass. We ruled out traumatic lesions and soft tissue abscess during the initial presentation with X-ray and ultrasound. Blood tests were suggestive of an infective pathology. As the ultrasound was normal in the initial presentation, we organised an MRI in the second admission, which showed evidence of osteomyelitis. We started broad-spectrum intravenous antibiotics initially and changed to intravenous benzylpenicillin following the identification of GAS in blood culture.

In children, osteomyelitis is mainly haematogenous in origin. Surgery and trauma are other common predisposing causes. Our child had a sore throat with evidence of pharyngitis, which may have been a potential cause of GAS bacteraemia.

GAS causes invasive infections with significant mortality and morbidity.¹⁰ The incidence of GAS bacteraemia and invasive infections in all ages is two to four cases per 100 000 per year.^{11 12} The risk of invasive GAS infection is highest in infancy.¹⁰ GAS accounts for 15%–30% of cases of sore throat in children, with a peak incidence in ages 5–15 years,¹³ up to one–fifth of children may be asymptomatic GAS carriers.^{14 15} GAS causes up to 10% of paediatric osteomyelitis;¹⁶ however, there are no published case reports of GAS causing clavicular osteomyelitis.

There are no consensus guidelines on the management of paediatric osteomyelitis.¹⁷ However, the current evidence stresses the importance of administering antibiotics as per the sensitivities of the causative pathogen. It is recommended to start empirical treatment based on the local microbiology data. Flucloxacillin and cephalosporins are used empirically in children above 1 year of age, as S. aureus is the most common organism causing osteomyelitis in this age group. Osteomyelitis is usually treated with antibiotics for up to 4–6 weeks.^{9 18} Surgery is advocated when there is any clinical evidence of local pus accumulation, surgery should also be considered when there is no clinical improvement or clinical worsening despite treatment with appropriate antibiotics.⁹

In our case, we started empirical ceftriaxone and flucloxacillin for 48 hours; we then changed it to intravenous benzylpenicillin following isolation of GAS. The child had intravenous benzylpenicillin for 5 days followed by 5 days of oral cephalexin. Surgery was considered when the child was readmitted with swelling in the region of the left clavicle, and MRI showed evidence of osteomyelitis with soft tissue phlegmon and subperiosteal collections. The child thereafter had intravenous ceftriaxone for 2 weeks followed by 4 weeks of oral penicillin. The child showed good clinical improvement with no sequelae noted postsurgery. The total duration of antibiotic treatment in our case was 8 weeks.

CONS is a known causative agent in prosthetic joint and device-related osteomyelitis.¹⁹ In our child, the isolation of CONS was considered to be a skin contaminant.

No penicillin resistance is reported in GAS, and therefore early identification of this organism helps in early initiation of appropriate treatment.²⁰ Osteomyelitis of clavicle is a rare clinical condition, and to our knowledge, this is the first case report of acute osteomyelitis of the clavicle due to GAS. This highlights the importance of identifying the microbial aetiology in these children to ensure early initiation of treatment with appropriate antibiotics leading to good symptom resolution.

Learning points.

• Osteomyelitis of the clavicle must be considered in children presenting with swelling in the region of the clavicle.

• Group A Streptococcus is a causative agent in osteomyelitis of the clavicle in paediatric age group.

• Identifying the microbial aetiology in these children is important to ensure early initiation of treatment with appropriate antibiotics.