We report the case of D.A. a 3-year-old boy, born in Peru and moved to Italy with his family when he was 18 months old. He had no relevant past medical history, apart from febrile seizures at 9 months of age.
When moved to Italy, D.A. and his family were hosted by friends in a small house in Milan suburbs. During their stay, D.A. and one of the hosts were diagnosed with scabies and treated with local application of permethrin. Unfortunately, D.A. relapsed a couple of months later, but this time his parents gave him no medications.
About one month after the scabies recurrence, he was brought to the Emergency Department because of a 4-day history of fever, right thigh pain and refusal to walk. He has had severe and diffuse itching for many weeks. At medical examination he looked generally unwell, pale-looking and a bit irritable. His right thigh was extremely painful on palpation, knee flexion was lost, while no limitations in hip movements were evident. He was not able to stand and walk. No local signs of impetiginization were found, but multiple crusted-papular lesions were present on lower limbs and abdomen as well as many scratch lesions.
Blood tests showed neutrophilic leucocytosis (white blood cells 14.600/mm3 with absolute neutrophil count 10600/mm3), significantly increased C reactive protein (CRP) (118 mg/L, nv < 10 mg/L), normal procalcitonin (0.57 µg/L, nv < 0.5 µg/L ), and mildly elevated liver enzymes (ALT 110 U/L, AST 96 U/L). Fibrinogen was also elevated (917 mg/dL), as well as D-dimer (973 ng/mL). Right hipbone and femur X-rays showed no bone fractures, hip and knee ultrasounds were negative. A contrast enhancement MRI of the pelvis and bilateral tights, under-sedation, was performed. MRI demonstrated abnormal bone marrow signal intensity, consistent with osteomyelitis, in the metaphysis and distal diaphysis of the right femur, which appeared inhomogeneous in relation to the presence of oedematous regions and hypo/avascular areas. The periosteum was elevated due to an associated subperiosteal purulent collection and there was concomitant pyomyositis and fasciitis of the distal right thigh and an abscess within the obturator externus muscle of the contralateral limb (Fig. 1A-B).
D.A. was admitted to our Paediatric Department. After obtaining blood cultures, an empirical combination of intravenous vancomycin and cephazolin was started. Since skin lesions suggested a recurrence of scabies, D.A. was placed in contact isolation. 48 hours after starting the antibiotics D.A. was still febrile and his general conditions worsened. Based on muscular and soft tissue involvement in MRI images, intravenous metronidazole was added to the ongoing antibiotic therapy to ensure better coverage for anaerobic bacteria. Trans-thoracic echocardiogram was negative for valvular vegetations. Blood tests showed raising of CRP (346.5 mg/L) and procalcitonin (6.5 µg/L), blood cultures turned positive for Methicillin-Resistant, Vancomycin-Susceptible Staphylococcus aureus. By the fifth day on the antibiotic course, D.A. became afebrile and his general conditions improved significantly. In the following days thigh pain also resolved and no more limitation or pain at knee flexion were noted. CRP turned negative on 10th day of antibiotic therapy, as well as liver enzymes, fibrinogen and D-dimer. Metronidazole was stopped after 10 days, while cephazolin was continued for 4 weeks. An 8-week course of intravenous vancomycin was completed. X-rays of femur, performed during third week of hospitalization, showed a mixed pattern of erosion and sclerosis at meta-diaphyseal region and periosteal reaction at diaphyseal region. D.A. started walking after 4 weeks of hospitalization. The diagnosis of acute bacterial osteomyelitis of the right femur with concurrent cellulitis, pyomyositis and fasciitis was done and, despite a negative personal medical history, we performed a first-line immunologic screening (Ig levels and lymphocyte phenotyping) that resulted normal.
During hospitalization the diagnosis of a recurrence of scabies was confirmed by a dermatologist since many scabies mites in burrows were found at dermoscopic evaluation. Another course of local therapy with permethrin was administered and ivermectin was also prescribed to all households. Scabies resolved and we did not observe any other recurrence during hospitalization.