DISCUSSION
AML is a haematological malignancy characterised by clonal expansion of myeloid precursors4. The skin manifestations in AML are variable and less well described especially in children5. SS or acute neutrophilic dermatosis is characterised by rapid onset of red, raised and often painful skin nodules or plaques often accompanied with fever and neutrophilia. The distribution of these lesions are characteristic with involvement of limbs, head and neck; less frequently the trunk and rarely mucosal surfaces2. Our case had SS in the background of a relapsed leukaemia (AML) which was initially unrecognised due to its clinical rarity. However, with no response to conventional chemotherapy, a histological evaluation was undertaken which prompted the diagnosis of SS.
SS is classified based on underlying clinical illness as classical/ idiopathic SS, malignancy associated SS and drug induced SS6. Malignancy associated SS may present prior to, at the onset, after the diagnosis or at recurrence of malignancy. Myeloid malignancy is one of the commonest cancers associated with SS7,8. In addition, treatment modalities utilised in haematological malignancies including granulocyte colony stimulating factor (G-CSF), granulocyte macrophage colony stimulating factor (GM-CSF), hypomethylating agents including azacytidine or decitabine are implicated in drug induced SS9. Our case presented with the skin lesions at the relapse of AML. However, the child received Azacytidine in the salvage chemotherapy which may have contributed to persistence of lesions post the salvage chemotherapy. Our case hence best describes a combination of paraneoplastic SS and drug induced SS. Understanding the inciting agent for SS is hence critical in treatment as it would define natural course of SS.
The etio-pathogenesis of malignancy associated SS is not well known. It is hypothesised that the alteration in various pro and anti-inflammatory cytokine (interleukin, tumor necrosis factor alpha, interferon) drives the neutrophilic infiltration of dermis2. The primary management of SS is treatment of underlying condition. However, systemic glucocorticoids are the most common first line agent recommended at a dose of 1-2 mg/kg prednisolone for 1-2 weeks and slow taper over 4-6 weeks9. Potassium iodide and colchicine are other first line agents, sometimes shown to be more efficacious than steroids9. Cyclosporine, indomethacin, doxycycline and dapsone have also been tried in management of SS often as second line agents when non responsive to steroids or colchicine5,7,9. In our case, there was rapid clinical response to glucocorticoids initially but skin lesions flared on tapering steroids. Colchicine was used for a total of 4 weeks following which there was complete resolution of lesions.
A concise review of published literature of malignancy associated SS has been presented in Table 1. In most of the studies, early identification and prompt treatment with steroids or colchicine has resulted in good initial response although recurrence has been implicated in a proportion. Outcome of malignancy has not been described in all studies and there is no evidence to suggest association of SS to have any prognostic implication in outcomes of malignancy. It is further imperative to have a more published literature and prospective data on outcomes of malignancy (in the background of SS) to have better consensus.
To conclude, our case highlights a rare cutaneous manifestation associated with AML. Astute clinical suspicion along with pursual of histological evaluation is the cornerstone for diagnosis of SS. Early identification aids treatment and helps achieve complete clinical response.