Keywords
Chemotherapy - multifocal pyomyositis - rhabdomyosarcoma
Introduction
Pyomyositis, purulent infection of skeletal muscle, is a rare infectious disease.
It is more common in tropical regions. It has a subacute course. Its pathogenesis
is not well elucidated. Immunosuppression due to diabetes mellitus, HIV infection,
prolonged use of corticosteroids, hematological malignancies, chemotherapy, chronic
renal failure, or cirrhosis may be predisposing conditions. Pyomyositis as a complication
of chemotherapy for nonhematological malignancies is extremely rare.
Case Report
A 27-year-old male, tobacco chewer, not a known case of any chronic illness, presented
in January 2016 with left-sided upper neck swelling for 2 months. His performance
status on Eastern Cooperative Oncology Group scale was 1. Examination revealed a conglomerate
nodal mass in the left side of neck extending from level 2 to 4. Fine-needle aspiration
cytology suggested metastatic poorly differentiated neoplasm. Contrast-enhanced computed
tomography (CECT) scan of the neck and thorax revealed multiple left-sided neck nodes
in all stations, largest measuring 6.2 cm × 4.2 cm at Level II. Positron emission
tomography-CT scan showed conglomerate left cervical lymph nodes and left supraclavicular
lymph nodes. Biopsy from cervical lymph node revealed alveolar rhabdomyosarcoma with
rhabdomyoblastic differentiation. On immunohistochemistry, the tumor cells were diffusely
positive for CD56, desmin, and myogenin while negative for AE1/AE3, p63, synaptophysin,
Melan-A, HMB-45, chromogranin, and leukocyte common antigen. He was planned for neoadjuvant
chemotherapy followed by locoregional therapy. He received the first cycle of chemotherapy
with vincristine, etoposide, and ifosfamide with mesna (VIME). Injection Vincristine
was repeated one week later. He presented on day 23 after first cycle of VIME with
pain in the right leg for 3 days and swelling on the posterior aspect of the left
thigh for 2 days. There was no history of trauma. Examination revealed swelling and
tenderness in the right calf, feeble pulsation in the right dorsalis pedis artery,
and two distinct nontender soft lumps, 3 cm × 2 cm each, located posteriorly on upper
one-third of the left thigh. He was hemodynamically stable and had fever 102 F. Ultrasound
of lower limbs revealed bulky right gastrocnemius muscle appearing darkly hypoechoic
and showing posterior acoustic enhancement suggestive of myositis with early changes
of necrosis. Neither liquefied collection nor any evidence of deep vein thrombosis
was seen. Targeted ultrasound at the sites of swelling in the left thigh revealed
collection with moving internal echoes in the subcutaneous plane and surrounding hyperechoic
fat suggestive of inflammation without the involvement of the underlying muscles.
Blood investigations revealed a total leukocyte count of 41,000/μL, Grade 1 transaminitis,
and normal renal functions. CECT scan of bilateral lower limbs revealed multiple peripherally
enhancing abscesses in the muscle plane in both lower limbs involving the right vastus
medialis, left adductor magnus, right gastrocnemius, and left tibialis posterior [Figure 1] and [Figure 2]. He was hospitalized and started on intravenous antibiotics after drawing blood
for culture. During hospital stay, he was treated with antibiotics – cefepime-tazobactam,
meropenem, amikacin, teicoplanin and clindamycin. He responded to antibiotics. Serial
ultrasound examinations showed the formation of abscess. Pus was aspirated twice under
ultrasonographic guidance from the left thigh, right gastrocnemius, and right vastus
medialis. Open surgical debridement of pus from the right gastrocnemius and right
vastus medialis was performed after 10 days of hospital stay [Figure 3]. Pus culture showed Streptococcus species on one occasion, sensitive to amikacin,
cephalexin, and azithromycin; on another occasion, pus culture showed Staphylococcus
sensitive to amikacin, ofloxacin, and cephalexin. Blood culture was sterile. He was
discharged after 2 weeks of hospitalization. After discharge, he was started on oral
metronomic chemotherapy with cyclophosphamide and etoposide for 2 weeks. After the
conclusion of metronomic chemotherapy, he was planned for three cycles of vincristine,
cyclophosphamide, and dactinomycin as neoadjuvant chemotherapy followed by locoregional
therapy and adjuvant chemotherapy. He has completed his neoadjuvant chemotherapy with
good tolerance. The neck masses have completely resolved.{Figure 1}{Figure 2}{Figure
3}
Figure 1: Axial (a) and sagittal (b) reformats of the patient with peripherally enhancing
abscess in the right gastrocnemius muscle
Figure 2: Same patient with similar peripherally enhancing abscesses in the right
vastus medialis (a), the left tibialis posterior muscle (b), and small abscess in
the left adductor magnus muscle (c)
Figure 3: Intraoperative picture of the opened cavity (a) in the right gastrocnemius
muscle showing a cavity with white thick shaggy walls. About 30 ml of hemorrhagic
tinged pus was aspirated (b)
Discussion
Pyomyositis, as a complication of chemotherapy, has been rarely reported. It has been
reported in patients of acute lymphoblastic leukemia,[1] acute myeloid leukemia,[2] myelodysplastic syndrome,[3] multiple myeloma, endometrial cancer,[4] lung cancer,[5] breast cancer,[6],[7] retroperitoneal teratoma,[8] colon cancer,[7] and glottic cancer.[7] Anthracyclines,[6] vinca alkaloids,[1] corticosteroids,[1] and taxanes [4] have been implicated in previous reports. The initial symptoms of myalgias can be
confused with vincristine-induced pain. In the early stage of pyomyositis, examination
does not reveal any specific findings. Signs such as fever, chills, and erythema are
uncommon. Hence, early diagnosis of pyomyositis is difficult. Due to the delay in
diagnosis, complications such as compartment syndrome, arthritis of adjacent joints,
multiple muscle abscesses, and sepsis may occur. This patient received vincristine
and presented with multiple muscle abscesses in both lower limbs. In early stages,
ultrasonography reveals only altered echogenicity, which is nonspecific. In the late
stage of suppuration, fluid collection may be seen. Staphylococcus aureus is the most
common pathogen, followed by Streptococcus.[9] Other organisms isolated include Bacteroides fragilis, Stenotrophomonas maltophilia,[3] pneumococci, Haemophilus influenzae, Gram-negative enteric bacilli, and anaerobes.
In this patient, Staphylococcus and Streptococcus were isolated in pus culture. Blood
cultures are positive in 5%–10% patients only. This patient had no growth in blood
culture. Some patients are cured with antibiotics alone,[10] whereas others require drainage of pus. This patient was treated with antibiotics
for total 4 weeks, ultrasound-guided aspiration of pus, and open surgical debridement.
This report highlights an unusual focus of infection – multifocal pyomyositis after
chemotherapy for rhabdomyosarcoma. When a patient on chemotherapy presents with limb
swelling and tenderness, pyomyositis should also be considered in the differential
diagnosis apart from cellulitis, deep vein thrombosis, and osteomyelitis.
