Hypogammaglobulinemia Causing Multiple Abscesses and Osteomyelitis of Calcaneus Following a Heel Puncture in a Preterm Neonate

Osteomyelitis is a challenging diagnosis for a neonate. It might result from hematogenous spread or direct extension of a skin infection. The most common organism is Staphylococcus aureus. Preterm infants are at high risk for osteomyelitis because of their immature immune system, hypogammaglobulinemia, frequent blood draws, and invasive monitoring and procedures. We report a case of a male neonate born at 29 weeks by cesarean section, requiring intubation and transfer to the neonatal intensive care unit (NICU). At 34 weeks, he was noted to have an abscess in the lateral aspect of the left foot, which required incision, drainage, and antibiotic coverage of cefazolin as S. aureus was sensitive to penicillin. Four days later (34 + 4 weeks), a left inguinal abscess was noticed, which grew Enterococcus faecium on drainage, which is considered a contaminant initially, but one week later, another left-sided inguinal abscess was noticed growing E. faecium, and the patient was subsequently treated with linezolid. Immunoglobulin levels were found to be low for IgG and IgA. After two weeks of antibiotics, a repeat x-ray of the foot demonstrated changes likely due to osteomyelitis. The patient received seven weeks of antibiotics targeting methicillin-sensitive staphylococcus and three weeks of treatment with linezolid for an inguinal abscess. A repeat x-ray of the lower left extremity after the patient received one month of antibiotics in an outpatient setting showed no signs of acute osteomyelitis in the calcaneus. Immunoglobulin levels continued to be low during the outpatient immunology follow-up. During the third trimester of pregnancy, the transfer of maternal IgG across the placenta begins, leading to lower IgG levels in premature infants and predisposing them to severe infections. The usual site of osteomyelitis is the metaphyseal region of the long bones, but any bone can be affected. The depth of penetration of the puncture site during routine puncture of the heel can cause a local infection. Early x-rays can aid in diagnosis. Antimicrobial treatment is frequently administered intravenously for two to three weeks and then switched to oral medication.