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X MONTH APRIL library at www . ausdoc . com . au / therapy-update
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2022
2023
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DermNet NZ |
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Investigations
Serum inflammatory markers are elevated with CRP at 53mg / L ( normal : 0-8 ), leucocytosis with a white blood cell count of 14.8x10 9 / L ( normal : 4.0-11.0 ) and raised neutrophils at 11.3x10 9 / L ( normal : 2.0-8.0 ).
There is a mild microcytic anaemia with haemoglobin at 122g / L ( normal 130-165 ), a red blood cell count of 3.91x10 12 / L ( normal : 4.50-6.50 ), and a mean corpuscular volume of 76fL ( normal : 80-99 ). Iron studies show iron saturation is 8 % ( normal 20-50 %), with a normal ferritin of 122 µ g / L ( normal 30-620 ). EUC and LFTs are normal . Stool microscopy , culture and sensitivity reveals blood and inflammatory cells are present , but culture is negative , including for clostridium and giardia .
At this point , the working differential diagnoses shift to include iron deficiency anaemia , post-asthma diarrhoea and post-COVID-19 syndrome diarrhoea , in addition to IBD .
Diagnosis
Mark is referred for a colonoscopy . Unfortunately , this is substantially delayed due to the hospital accepting fewer cases due to COVID-19 . Faecal calprotectin is then requested and is elevated at 1081 µ g / g (> 100 µ g / g is abnormal , > 250 µ g / g can be suggestive of IBD ). After five months , Mark ’ s colonoscopy confirms Crohn ’ s disease .
Mark is referred to a gastroenterologist who commences infliximab resulting in instant improvement . One year after diagnosis and treatment , Mark ’ s faecal calprotectin is 32 µ g / g .
Discussion
Mark ’ s case highlights the various differentials to be considered when managing post-infective diarrhoea as well as some of the diagnostic and logistic challenges faced by practitioners and patients during the COVID-19 pandemic . 1
Diarrhoea and abdominal discomfort following a course of antibiotics is a common presentation of C . difficile infection . The diagnosis of C . difficile requires presence of diarrhoea ( defined by three or more unformed stools within 24 hours ), 2 positive
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stool test for toxicogenic C . difficile or its toxins OR colonic / histopathological findings demonstrating pseudomembranous colitis . 2
Diarrhoea and abdominal pain are also known sequelae after COVID-19 . 3 , 4 It can be difficult to establish whether diarrhoea is due to COVID-19 or another cause . In this case , the treating GP considered COVID-19-related diarrhoea as a ‘ diagnosis of exclusion ’ and attempted to investigate other causes to determine whether this was an appropriate diagnosis .
The presence of blood in the stools was an important finding in this case , prompting prompt colonoscopy referral . The flow-on effects of pandemic measures resulted in an untimely delay , to diagnosis and appropriate management and care . In hindsight , it could have been beneficial to have ordered the faecal calprotectin sooner . However , it should be noted that there are other non-IBD causes of raised faecal calprotectin , including infections and ischaemia .
Prednisolone can be used to manage asthma exacerbations as well as cases of IBD . 5 , 6 In retrospect , in this case use of prednisolone for asthma also resulted in an improvement in the Crohn ’ s symptoms . 7 This masking of IBD symptoms meant that it took several GP visits for the gastrointestinal significance to become clear , which also contributed to the delay in diagnosis .
References on request from kate . kelso @ adg . com . au
Learning points
• Consider a wide range of differential diagnoses when investigating the cause of diarrhoea
• Note that C . difficile infection is an important cause of diarrhoea after antibiotic use that should be ruled out
• Corticosteroid use can mask the symptoms of inflammatory diseases such as IBD and potentially lead to delays in diagnosis
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The patient had episodes of cough , wheeze , yellow sputum and abdominal bloating .
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What is the most likely diagnosis ?
a Livedo reticularis b Allergic contact dermatitis c Poikiloderma vasculare atrophicans d Erythema ab igne
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For details , email medical co-editor kate . kelso @ adg . com . au
ANSWER The answer is d . Erythema ab igne ( EAI ) is characterised by localised areas of reticulated ( net-like ) erythema and hyperpigmentation as a result of chronic exposure to infrared radiation in the form of heat . 1
It was once commonly seen in the elderly who sat close to open fires or heat stoves . The introduction of central heating has reduced the prevalence of this type of EAI . However , it is still found in individuals exposed to heat from different sources . Nowadays , it is more strongly associated with chronic exposure to electronics , such as laptops or space heaters . 2 , 3
The rash begins as a transient macular erythema arranged in a broad , reticulated pattern that blanches easily .
Prolonged and repeated exposure causes areas of reticular erythema to persist and over time become hyperpigmented .
The size and shape of the lesion often approximates to that of the heat source .
Affected skin and underlying tissue may start to thin , rarely sores will develop . In patients with severe long-standing EAI , poikilodermatous changes can ensue . 3
Treatment entails removing the source of chronic heat exposure . If the area is only mildly affected with slight erythema , the condition will gradually resolve over several months . In more severe varieties with hyperpigmentation and atrophic skin , resolution is unlikely . In such cases , there is a small long-term risk of squamous cell carcinoma or Merkel cell carcinoma developing within the EAI lesion , the latent period may be 30 years or more .
Any persistent sore that does not heal or a growing lump within the rash should be biopsied to exclude skin cancer . Abnormally pigmented skin can persist for years and treatment with topical tretinoin or laser therapy may improve cosmetic appearance . 1 , 2 , 3
Dr Paul Muthiah is a GP on the Central Coast , NSW and medical co-editor of Australian Doctor .
References on request from paul . muthiah @ adg . com . au
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