Commentary on Kapoor et al.

The case report by Kapoor and colleagues illustrates the difficulty in differentiating congenital from postnatally acquired tuberculosis (TB) in young infants. The incubation period for congenital TB is generally measured in weeks, rather than months, and the mother may have previously undiagnosed genitourinary TB; intrauterine growth restriction may be seen. Modes of transmission to the young infant also may include aspiration of amniotic fluid, hematogenous spread via umbilical vessels, direct contact (eg, tuberculous mastitis), or postnatal airborne transmission.

Nonetheless, the clinical presentation of young infants with congenital and postnatally acquired TB is similar, and many of the salient features are described in this case report. These include short incubation period, high risk of dissemination, radiographic findings, high organism load, and need for a high index of suspicion.

The short incubation period for young infants means that the child may be the first in the family to be diagnosed. This may be particularly true in resource-poor nations, where evaluation of infertility may not be common and maternal medical care outside the intrapartum period may not be easily accessed. A high risk of dissemination is seen, most commonly to the meninges (seen in up to one-third of cases); in this child, involvement of the reticuloendothelial system was seen. Chest radiographs are abnormal in the majority of children; approximately one-half have a miliary pattern with intrathoracic lymphadenopathy also commonly seen. Rapidly progressive pulmonary TB can result in cavitation. The general pauci-bacillary nature of childhood TB is not the rule in miliary TB, where an acid-fast bacilli (AFB) culture yield often exceeds 70%. Obtaining adequate cultures before initiation of antituberculous therapy is essential, as cultures from relatives may be unavailable at the time of the infant's evaluation. Finally, TB needs to be entertained on the differential diagnosis. Radiographic findings can overlap with hyaline membrane disease and congenitally acquired viral and bacterial infections; in the human immunodeficiency virus-infected infant, this differential diagnosis is even more extensive, including Pneumocystis jirovecii, among other pathogens. Adjunctive tests often helpful in the older child, such as the tuberculin skin test or interferon gamma release assays, are insensitive in this age group, particularly in the face of overwhelming disease. Although AFB smears are sometimes positive, obtaining a thorough family history, including maternal gynecological history (eg, recurrent miscarriages), may be more immediately helpful than microbiologic testing. In countries with high TB prevalence rates, identification of multiple adults with TB disease (potentially with differing drug-susceptibility patterns) is possible. This emphasizes the importance of obtaining microbiologic diagnosis and drug-susceptibility testing in children.

The evaluation of an infant with possible TB disease should include obtaining respiratory cultures, evaluation for tuberculous meningitis, prompt initiation of antituberculous therapy, and a thorough contact investigation. If congenital TB is suspected at the time of delivery, the placenta should be examined by histopathology and AFB culture. A high index of suspicion and timely initation of appropriate therapy can decrease morbidity and mortality in this vulnerable population.