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ausdoc. com. au 12 DECEMBER 2025
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SPOT DIAGNOSIS
Sunburn or something more fishy?
MORE ON THIS DIAGNOSIS ONLINE ausdoc. com. au / spot-diagnosis
PETE, a 35-year-old, is seen urgently via telehealth to review a red, hot, itchy rash on his back that developed 30 minutes ago( pictured). A headache coincided with rash onset but has subsided and the itch has eased after a self-administered dose of antihistamine. There are no weals and no other systemic symptoms. Pete is otherwise well, with no past history of note, no known allergies and no recent medication use.
He spent five hours this morning fishing and wonders if he got sunburnt as it was an unexpectedly hot and sunny outing on the tinnie. He was wearing sunscreen and a long-sleeved shirt and hat but got caught out without an esky and ice to store the fish. He ate some of the mackerel catch about one hour before symptom onset.
His wife also had a taste and experienced similar symptoms, which settled completely with antihistamine administration.
not attend school for seven days after jaundice onset and practise good hand hygiene.
Follow-up and further management
Seven days later, Nat re-presents, tearful and distraught, asking for a medical certificate for work. The day prior, Maya had become somewhat drowsy, started vomiting, and appeared confused. Nat heeded the safety netting instructions and took Maya to the local ED, where she was urgently referred to a tertiary paediatric centre. Maya was diagnosed with acute liver failure and is awaiting urgent liver transplant assessment.
Diagnosis
The diagnosis is acute liver failure secondary to fulminant hepatitis A infection.
Discussion
Hepatitis A infection in children is typically a mild, self-limiting illness, and if symptomatic, characterised by non-specific symptoms such as fatigue, anorexia and jaundice. Approximately 70-80 % of susceptible adults and children aged six and over have symptomatic hepatitis A infection, whereas symptomatic hepatitis occurs in around 30 % of infected children under six years. 1
This case illustrates the rare but potentially devastating complication of acute liver failure, which occurs in less than 0.1 % of cases in children in developed regions. 2 In contrast, in children who reside in endemic regions, hepatitis A is one of the most common causes of paediatric acute liver failure. 3
While the majority of paediatric hepatitis A cases follow a benign course to complete recovery, clinicians and caregivers must remain vigilant for signs of deterioration.
The differential diagnosis of jaundice in a paediatric patient is broad and can be categorised into infectious, haemolytic, and hepatic causes( see table 2).
Table 2. Differential diagnosis of jaundice in paediatric patients
Urine dipstick is a simple and useful test that can help formulate a more specific differential diagnosis and hence aid appropriate investigation ordering, and limit unnecessary investigations.
This case highlights the importance of clear safety netting. It also underscores the importance of travel vaccinations. In Australia, most hepatitis A infections now occur in unvaccinated travellers. 4 Hepatitis A vaccination is recommended for any travellers to endemic regions who are aged one year or older. 5 Vaccination is also recommended for Indigenous children who reside in the NT, Queensland, SA or WA; those with chronic liver disease or developmental disabilities; and people at occupational or lifestyle risk. 5
Hepatitis A is a notifiable disease, and local public health services should be contacted and will provide advice or co-ordinate contact tracing and post-exposure prophylaxis. In identified cases, unvaccinated household contacts should receive post-exposure prophylaxis within 14 days of exposure. For most, hepatitis A vaccine is recommended, although select groups require human immunoglobulin. 5
Clinicians should maintain a high index of suspicion for hepatitis A in any unvaccinated child presenting with jaundice after travel to endemic regions, while also being aware of the rare but serious possibility of progression to acute liver failure. This case serves as a reminder that even common infections can have rare but devastating complications, particularly in the context of global travel patterns and variations in vaccination coverage.
Outcome
Fortunately, Maya did not need a liver transplant. She was managed in the high dependency unit, and after a prolonged inpatient admission of five weeks, was discharged home. Six months later, she is back to full health.
References on request from kate. kelso @ adg. com. au
Category Most common causes Less common but important causes 1. Infectious Hepatitis A( most common) Hepatitis B, C, E
Epstein-Barr virus
CMV 2. Haemolytic G6PD deficiency Autoimmune haemolytic anaemia
Hereditary spherocytosis Sickle cell crisis( if known sickle cell disease) 3. Hepatic Drug-induced liver injury Autoimmune hepatitis
Wilson’ s disease( age-appropriate) Non-alcoholic fatty liver disease
The patient had developed scleral icterus.
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Which is the most likely diagnosis?
a Sunburn b Solar urticaria c Scombroid poisoning d Seafood anaphylaxis
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Spot Diagnosis?
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Spitzer D. An itchy rash after eating tuna BMJ 2022; 376: e068817
ANSWER The answer is c. Scombroid poisoning occurs after ingestion of contaminated dark-meat fish. It is classically associated with finfish from the Scombridae and Scomberesocidae families, such as tuna, mackerel, skipjack and bonito. Cases have also been reported after ingestion of other fish types, including mahi-mahi, bluefish, amberjack, swordfish, marlin, herring, sardines, anchovies, salmon, tilapia and trout. 1 Scombroid poisoning occurs when fish are improperly stored— namely, at temperatures above 4 ° C) after being caught. At higher temperatures, bacterial overgrowth occurs, leading to conversion of histidine into scombrotoxin, of which histamine is the main component. Toxic levels of histamine can accumulate within 2-3 hours in fish stored at temperatures of 15 ° C or higher. In resource-rich regions, scombroid is more likely to occur following consumption of a recreational catch rather than commercial fishing. 1, 2
Contaminated fish may smell and appear fresh but may taste peppery, spicy or bubbly. Symptoms typically occur within 30 minutes to two hours of consumption. The most common feature is cutaneous flushing of the face, neck and upper torso, with an associated erythematous, hot, itchy rash. This is a form of urticaria but is not typically associated with wealing. 2 Rash and flushing may be the only symptoms. Other common features include diarrhoea, nausea, vomiting and headache. 1, 2 More serious cardiorespiratory features may occur, particularly in those with pre-existing respiratory or cardiac disease because of bronchospasm, coronary vasospasm, hypotension and arrhythmia. 2
The diagnosis is clinical. If available, the suspected causative fish can be examined for elevated histamine levels to confirm the diagnosis. 2
In uncomplicated cases, symptoms improve or resolve within 10-15 minutes of administration of a fast-acting H1 antihistamine. For those with significant gastrointestinal symptoms or who do not respond rapidly to a H1 antihistamine, a dose of H2 antihistamine— for example, famotidine— may be of benefit. 1, 2
The need for further or urgent medical attention depends on the clinical presentation and response to initial measures. Any cases associated with cardiorespiratory features or persistent symptoms despite administration of antihistamines warrant urgent ED review.
In this case, sunburn is unlikely given the distribution of the rash on sun-protected areas. Solar urticaria typically causes weals, usually within minutes of sun exposure, and resolves within minutes to hours of cessation of exposure. Allergy is a key differential to consider in cases of scombroid, and the clinical picture may be identical, although anaphylaxis is more likely to be associated with weals. A lack of fish allergy and clustering among people who ate the same fish are more suggestive of scombroid poisoning. Allergy testing for skin prick or oral challenge may be warranted if there is ongoing diagnostic uncertainty or concern for seafood allergy. 1, 2 Dr Kate Kelso is a GP and medical editor at Australian Doctor. References on request from kate. kelso @ adg. com. au