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.