Neonatal pustular and vesiculobullous eruptions — formative SAQs

SAQ 1 (10 marks)

A ten-day-old term neonate presents with a one-day history of fever, lethargy and poor feeding, and is found to have clustered vesicles on an erythematous base on the scalp at the site of a fetal scalp electrode. The baby was born vaginally to a mother who reported a first episode of genital herpes in the week before delivery. [6]

Question: Outline the diagnosis, the immediate investigations, and the management of this neonate, including the aciclovir regimen and the principle that governs the decision to start it. (10 marks) [6] [7]

Model answer

Diagnosis and recognition (2 marks). The most likely diagnosis is neonatal herpes simplex. The clustered vesicles on an erythematous base at the scalp-electrode site, the fever and lethargy, and the maternal primary first-episode genital herpes near delivery (the highest-risk scenario for transmission) together make this herpes simplex until proven otherwise. This is a neonatal emergency. [6]

Immediate investigations (3 marks). Perform a full sepsis evaluation — full blood count and differential, C-reactive protein, blood culture, urinalysis and urine culture, and liver function tests looking for the hepatitis of disseminated disease. The herpes-specific workup is HSV PCR taken from surface swabs (conjunctiva, mouth, nasopharynx, rectum) and from any skin vesicle, blood PCR, and cerebrospinal fluid for cell count, protein, glucose and HSV PCR. PCR has replaced viral culture as the diagnostic standard because it is faster and more sensitive. [7] [6]

Management and the aciclovir regimen (3 marks). Start intravenous aciclovir at 20 mg/kg every eight hours promptly after taking samples, without waiting for the PCR results, because delayed aciclovir increases mortality and long-term neurodevelopmental morbidity. Add broad-spectrum antibiotics to cover neonatal sepsis while results are pending. The total duration is guided by disease category: 14 days for skin-eye-mouth disease and 21 days for central-nervous-system and disseminated disease, with follow-on specialist-led suppression and surveillance. Admit, monitor for disseminated disease, and involve paediatric infectious diseases. [6] [7]

The governing principle and safety-net (2 marks). The principle is that a vesicle on an ill neonate is herpes simplex until proven otherwise, and the well-or-ill call is the single most powerful discriminator in this topic — treatment cannot wait for the confirmatory test. On recovery, arrange the follow-up surveillance for recurrence and neurodevelopment, and coordinate with paediatric infectious diseases for the long-term plan. [6]