Figure 2 . The lesion was unchanged after four weeks . |
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causes include infection , inflammatory conditions , neoplasia , drugs and pregnancy . 1 , 2 , 3 The pathogenesis is poorly understood . It is generally
considered to be a delayed-type hypersensitivity
response to various antigens . Primary EN generally resolves spontaneously within several weeks without treatment . 1 , 2
An underlying cause must be ruled out , especially when EN is accompanied by other systemic findings . 2 Systems review , including for respiratory , gastrointestinal and constitutional symptoms , may provide diagnostic clues . 1 Respiratory features may point towards a streptococcal infection which is the leading aetiology , although TB and sarcoidosis are also potential causes . 1 , 3 Gastrointestinal symptoms may indicate inflammatory bowel disease . 1 , 2 A medication and travel history may point to drug-associated EN or possible exposure to endemic infectious organisms ( such as leptospirosis , brucellosis , Q fever and Hansen ’ s disease ). 1 Medications that may be associated with EN include oral contraceptives , penicillin , sulfonamides , bromides and iodides and , rarely , TNF-alpha inhibitors . 1
Immune system dysfunction and chronic inflammation may complicate T2DM . 4 Despite there being no established causal relationship between T2DM and EN , both involve complex interactions between the immune system , inflammatory , and metabolic pathways . 1 , 4 Therefore , it is logical that there may be a systemic association between the two conditions . Once other red flag conditions have been ruled out , it is reasonable to consider EN as an atypical clinical feature of poor glycaemic control .
Dermatological manifestations of T2DM such as diabetic dermopathy are well established . 5 Diabetic dermopathy , which also has a predilection to affect the shins , shares similar histological features with EN , as both involve
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What is the most likely diagnosis ?
a Atopic dermatitis
b Tinea corporis
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c Psoriasis
d Granular parakeratosis
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Figure 3 . After 12 weeks , the patient ’ s glycaemic control had improved and the lesion had almost resolved .
perivascular lymphocytic infiltrate . 6 There are distinct clinical differences between lesions in the two conditions as diabetic dermopathy progresses from rounded , dull , erythematous papules to well-circumscribed , atrophic , brown , scaly macules . 5
Outcome
Mike returns after 12 weeks . His glycaemic control is dramatically improved and now in target range . Examination of his right lower leg reveals that the lesion has almost completely resolved ( see figure 3 ).
References on request from kate . kelso @ adg . com . au
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ANSWER The correct answer is d . Granular parakeratosis is typified by brown-red scaly plaques , usually occurring in areas of friction , sweating and occlusion . Cases may be triggered by use of laundry or cosmetic products containing benzalkonium chloride . 1 This constituent , which has antimicrobial properties , can disrupt human cellular lipid membranes and induce proliferation and abnormal development of keratinocytes .
In this patient , a key clue is the appearance of the plaques after she washed her jumpers in an antiseptic laundry product . Since COVID-19 , there has been an increase in cases of granular parakeratosis associated with the use of antiseptic laundry products . 1
While atopic dermatitis does have a predilection for flexural surfaces , it typically presents as more chronic , intensely pruritic and erythematous , with some response to steroids . 2 Tinea corporis is characteristically asymmetrical and well-demarcated . It is scaly and plaque-like with a distinct erythematous border and central clearing . 3 This patient ’ s rash lacks a distinct ring-border and is symmetrical .
Psoriasis is an unlikely diagnosis as the rash does not involve the characteristic thick and erythematous plaques of psoriasis . 4 The location confined to the skin folds and history of washing underwear in antiseptic soap is more suggestive of granular parakeratosis .
The patient stopped using the antiseptic detergent containing benzalkonium chloride to wash her clothes . She was also treated with betamethasone dipropionate and calcipotriene foam twice daily . The rash had cleared at the next review .
References on request from kate . kelso @ adg . com . au
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