Congenital and perinatally acquired infections: SAQ

This infant presents the classic cytomegalic inclusion disease phenotype of congenital CMV: microcephaly with periventricular calcifications, petechiae and a 'blueberry muffin' rash of dermal haematopoiesis, and hepatosplenomegaly. The maternal flu-like illness at 10 weeks gestation is consistent with primary CMV infection in the first trimester - the highest-risk period for severe fetal disease. Rubella, syphilis, HIV, and hepatitis B are effectively excluded by the documented negative screens. ^[2]

Question 1 (10 marks)

Outline your diagnostic approach and the investigations you would perform to confirm congenital cytomegalovirus. ^[2]

The priority is to confirm congenital CMV within the diagnostic window. The gold standard is detection of CMV by polymerase chain reaction in urine or saliva collected within the first three weeks of life; after this window, postnatally acquired CMV (including from breast milk) cannot be distinguished from congenital infection. Send urine and saliva PCR now, and request CMV PCR on blood and cerebrospinal fluid as adjuncts. ^[1]

Perform a targeted broader workup to stage disease severity and exclude mimics: a complete blood count for thrombocytopenia and anaemia, liver function tests for hepatitis, and coagulation studies. Perform a lumbar puncture for CSF cell count, protein, glucose, and CMV PCR if the infant is stable. Obtain cranial ultrasound and, for better delineation of cortical and cerebellar involvement, a cranial MRI. Arrange an ophthalmology review for chorioretinitis, and audiology referral for diagnostic auditory brainstem response testing. If the diagnosis is considered after the three-week window, retrospective testing of the stored neonatal blood spot (Guthrie card) is the only reliable retrospective method, though it is less sensitive. ^[2]