drug hypersensitivity syndrome ( dhs ) , also known as drug rash with eosinophilia and systemic symptoms ( dress ) , is a severe drug reaction .
the syndrome can also be caused by other drugs , such as allopurinol , sulfonamides , beta - lactam antimicrobials , antidepressants , and nonsteroidal anti - inflammatory drugs .
allopurinol hypersensitivity syndrome ( ahs ) is characterized by rash , fever , and internal organ involvement .
we report a case of an exceptional presentation of agep as a manifestation of ahs .
a 67-year - old male was admitted to the dermatology department with history of widespread skin eruption since 10 days .
he was started on allopurinol ( 200 mg / day ) for hyperuricemia 8 weeks earlier .
clinical examination showed maculopapular eruptions involving trunk , arms and legs , as well as pinhead - sized follicular and nonfollicular pustules on patient 's face and trunk .
laboratory investigations revealed a white blood cell count of 13.2  10/l with atypical lymphocytes and hypereosinophilia ( eosinophil count 1.9  10/l ) .
iu / l ( reference range 340 ) and alanine aminotransferase 409 iu / l ( 345 ) .
barr virus , hepatitis b , c , hiv , parvovirus b19 and human herpesvirus 6 .
skin biopsy showed subcorneal spongiform pustules and some single scattered necrolytic keratinocyte [ figure 1 ] .
the superficial dermis was edematous , with mixed inflammatory infiltration , including numerous neutrophils and rare eosinophils consistent with the diagnosis of agep .
subcorneal spongiform pustules and some single scattered necrolytic keratinocytes the patient improved markedly within 72 h on prednisone 30 mg daily ( dose of 0.5 mg / kg body weight ) .
full dose corticosteroid therapy was continued for two weeks , and tapered by 2.5 mg every 57 days , with a total duration of 3 months .
causality assessment by the naranjo probability scale showed that ahs had probable causal association with the adverse effect .
allopurinol hypersensitivity syndrome is a rare adverse reaction characterized by a spectrum of cutaneous reactions and systemic manifestations .
ahs is more frequently associated with chronic renal insufficiency and concurrent use of thiazide diuretics .
the exact pathogenesis of this syndrome is yet unclear , but different hypothesis are proposed .
it seems to be related to the accumulation of allopurinol or oxipurinol a ( major metabolite of allopurinol ) in patients with renal insufficiency .
immunological factors , genetic factors , and human herpes virus - type 6 are also implicated .
cutaneous manifestations of hypersensitivity syndrome are heterogeneous , ranging from mild morbilliform exanthema to severe toxic epidermal necrolysis and stevens  johnson syndrome .
pustules in dhs differ from the typical pattern of agep , in which pustules are more numerous and predominant in main body folds .
we scored both the european registry of severe cutaneous adverse reaction ( regiscar ) criteria for dress and euroscar agep score .
the score was 7 for dress indicating a definite case and 5 for agep indicating a probable case .
the clinical features which most differentiated dress from agep in our patient were the delayed onset ( 8 weeks ) , protracted course and multi - organ involvement .
the first case of ahs with generalized nonfollicular pustulosis was described in a 47-year - old man .
the second is a 65-year - old man who developed ahs manifested as generalized follicular pustulosis mimicking agep .
allopurinol directly inhibits the lymphocytes enzyme purine nucleoside phosphorylase and may affect certain components of the immune system with an alteration of cd4/cd8 rate .
the concomitant release of several mediators from eosinophils and/or activation of neutrophils might be important for the clinical evolution of lesions , with appearance of pustules , or aggravation of skin detachment , as well as internal organ involvement in dress . a drug reaction leading to folliculitis and then pustule formation has also been proposed .
clinicians should be observant of cutaneous manifestations of hypersensitivity syndrome that may be a nonfollicular and/or follicular pustular eruption as well as the more commonly associated maculopapular rash or erythroderma .
 allopurinol hypersensitivity syndrome ( ahs ) is a severe drug reaction . 
 it is characterized by rash , fever , and internal organ involvement . 
 it may present in different clinical forms . 
 we present a case of acute generalized exanthematous pustulosis occurring as a manifestation of ahs . 
Introduction
Case Report
Discussion