Australian Doctor 4th August 2023 AD 4th Aug Issue | Seite 55

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SPOT DIAGNOSIS

Professor Dedee Murrell is head of dermatology at St George Hospital , Sydney , and conjoint professor at UNSW Sydney . This article was co-authored by Henry Tseng , a medical student at UNSW Sydney , and Dr Corey Stone , a dermatology research fellow at Premier Specialists , Kogarah , NSW , and St George Hospital , Sydney .

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The patient is a 72-year-old teacher who presents with pruritus affecting his upper back and scalp for the past seven days after cleaning a chicken coop . The pruritus causes him to scratch , resulting in excoriation . The itch disturbs his sleep and makes focusing on daily tasks difficult . He reports that he has previously had similar symptoms which have been self-limiting , resolving after a few weeks , but has not previously sought medical attention . He is not aware of any close contacts with similar symptoms . On examination , there is excoriation and erythematous papules and erosions on the back and scalp , with crusting and hypopigmented patches surrounding the sites of excoriations . The digital webs and groin are spared . There are no signs of bleeding or dermatitis .

a single severe stricture in the lower third of the main bile duct , which is stented . A repeat CT scan does not define a pancreatic mass .

Finally , an endoscopic ultrasound locates a mass in the uncinate process , and fine-needle biopsy confirms pancreatic ductal adenocarcinoma ( PDAC ). Although a staging laparoscopy confirms there is no peritoneal disease , the cancer is classified as borderline resectable given its proximity to a major blood vessel .

Discussion

Despite upper gastrointestinal symptoms that improve with esomeprazole , Andrew ’ s initial presentation is not typical of gastric pathology . Nor are the symptoms typical of either acute or chronic pancreatitis . While an elevated lipase suggests a range of pancreatic pathologies — such as acute or chronic pancreatitis , AIP and pancreatic cancer — it may occur in association with a range of non-pancreatic pathologies . 1 The absence of

an obvious pancreatic mass on initial and repeat imaging contributed to the diagnostic challenge .

AIP is an uncommon condition that accounts for up to 2 % of chronic and recurrent pancreatitis . 2 It is on the spectrum of autoimmune IgG4-related sclerosing disorders that may include pancreatic , thyroid , renal and salivary gland involvement . It usually responds well to corticosteroid therapy .

AIP and pancreatic cancer share similar features , including a preponderance to occur in older age , and present with obstructive jaundice , presence of a mass and elevated tumour markers . 3

It can be challenging to differentiate AIP from pancreatic cancer based on clinical and imaging findings . 2-4 Of the differentiating biomarkers , elevated IgG4 suggests AIP . 3 While extreme elevation of the tumour marker CA19-9 ( greater than 1000U / mL ) is highly specific to pancreatic cancer , an increase may also reflect biliary obstruction , cholangitis and AIP , as well as other gastrointestinal , thyroid and liver diseases . 4 , 5

Ideally , pancreatic cancer should be ruled out with histopathology before initiating treatment for AIP . 2 However , pancreatic biopsy is invasive , with risks including infection and bleeding . 6 In this case , definitive diagnosis of the pancreatic pathology is only obtained after endoscopic ultrasound and transduodenal fine-needle aspiration .

Only 15-20 % of PDAC are resectable at diagnosis . 7 PDAC has the highest mortality rate of the main pancreatic cancer types and is the fourth leading cause of cancer death in Australia . 5

Symptoms of pancreatic cancer may be non-specific , with insidious onset . It should be suspected when weight loss occurs in association with abdominal symptoms or back pain in individuals aged over 60 . 5

The absence of an obvious pancreatic mass on initial and repeat imaging contributed to the diagnostic challenge .

Risk factors include increasing age , obesity , smoking , longstanding diabetes and chronic pancreatitis . Approximately 5-10 % of patients with pancreatic cancer have a family history of the disease . 5

Outcome

Andrew ’ s borderline resectable pancreatic cancer is treated initially with FOLFIRINOX ( fluorouracil , leucovorin , irinotecan , oxaliplatin ) chemotherapy , followed by radiotherapy . Given the proximity of the lesion to the superior mesenteric veins , the planned surgery is an exploratory laparoscopy , with a view to a pancreatoduodenectomy and vascular reconstruction .

References on request from kate . kelso @ adg . com . au

It can be challenging to differentiate autoimmune pancreatitis from pancreatic cancer based on clinical and imaging findings .

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What is the most likely diagnosis ? a Lichen simplex chronicus b Prurigo nodularis c Chicken lice infestation d Scabies

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ANSWER The answer is c . Based on the clinical presentation , the most likely diagnosis is chicken lice ( also known as bird mites ) infestation . The recent exposure to a chicken coop and intense pruritus affecting his back and scalp are consistent with the typical clinical manifestations of chicken lice infestation . Excoriations , red papules , crusting and hypopigmented patches also support this diagnosis .

Scabies is an important differential to consider in the setting of severe pruritus and crusting . Unlike scabies , bird mites typically do not burrow beneath the skin . In addition , while scabies can affect various parts of the body , it typically involves the fingers , wrists , groin , buttocks and genitals . That said , microscopic examination of skin scrapings is warranted to confirm the diagnosis and to exclude other infestations .

Lichen simplex chronicus is also a contending differential cause in the setting of pruritus and excoriation ; however , lichen simplex chronicus tends to present as well-demarcated , lichenified erythematous plaques and patches rather than the scant papules seen in this patient ’ s case .

Prurigo nodularis is a potential cause of pruritic erythematous papules on the back ; however , the nodules in prurigo nodularis tend to be larger in diameter ( up to 2cm ), hyperpigmented , and often grouped .

Treatment of bird mite infestation involves measures to remove mites from the skin and manage associated symptoms or superinfection . All visible mites should be removed — loofah shower scrubs may assist . Emollients , coal tar products , topical steroids and oral antihistamines may help reduce itch . Bleach baths and oral antibiotics may be warranted for secondary infection . The use of full protective wear during coop cleaning may prevent reinfection .

References on request from kate . kelso @ adg . com . au