Sézary Syndrome

Epidemiology and Aetiology

Sézary syndrome is very rare, making up <5% of cutaneous T cell lymphomas (therefore at least 10 times less common than mycosis fungoides). It has a similar age of onset and no known aetiology. It can be considered a 'leukaemic version' of mycosis fungoides.

Natural History

The most significant problem experienced by patients is loss of the normal CD4+ T cell population; this leads to immunodeficiency and opportunistic infection. Disease is often widespread, with involvement of many visceral sites possible, with the unusual exception of the bone marrow.

Clinical Features

The presentation of Sézary syndrome is with rapid onset of generalised erythroderma. This is associated with generalised pruritis and alopecia. On examination patients usually have generalised lymphadenopathy.


Diagnosis is dependent on the finding of Sézary cells in the peripheral bloodstream. Sézary cells are the cerebriform cells seen in mycosis fungoides. A count over 1,000 cells per mm3 is required for diagnosis; without this finding the diagnosis is simply mycosis fungoides.

Tumour/Normal Tissue Features


The macroscopic lesions of Sézary syndrome are similar to mycosis fungoides.


There may be less dermatotropism seen in Sézary syndrome than mycosis fungoides. Otherwise the appearances are very similar. Immunohistochemistry findings are similar to mycosis fungoides.


On examination of the genome, there are often large deletions and translocations throughout most chromosomes (moreso than mycosis fungoides). This implies a higher level of genomic instability and perhaps the reason for the more rapid presentation.


By definition, all Sézary syndromes are Stage IV in the unique system used for mycosis fungoides/Sézary syndrome.

Stage Features
IA Patches, papules or plaques limited to < 10% of skin surface
IB Patches, papules or plaques covering > 10% of skin surface
IIA Patches, papules or plaques associated with early lymph node involvement (N1-2, see next table)
IIB One or two skin tumours, no nodes
III Erythroderma, with no nodal involvement, and < 1,000/μl circulating Sézary cells
IV High blood tumour burden (> 1,000/μl), extensive lymph node involvement (N3+) or visceral disease