Histiocytoid Sweet’s syndrome: a histological variant

Updated 19/03/17.

Sometimes, Sweet’s syndrome can occur in an unusual form. This is called a disease variant.

What is histiocytoid Sweet’s syndrome?

Histiocytoid Sweet’s syndrome is a rare histological variant of Sweet’s syndrome that is usually associated with certain medications, or cancer and blood disorders (35-55% of cases) (Wick and Bush, 2015). In regards to the latter, it normally occurs in association with a group of blood disorders called myelodysplastic syndromes (MDS) (Shalaby et al, 2016).

How many people have histiocytoid Sweet’s syndrome?

By May 2016, at least 72 cases of histiocytoid Sweet’s syndrome had been reported in medical literature (Arima et al, 2015; Kato et al, 2016; Miller et al, 2015; Shalaby et al, 2016).

How is histiocytoid Sweet’s syndrome different from Sweet’s syndrome?

In patients with histiocytoid Sweet’s syndrome, their biopsy results show something different from what you would normally expect to find in Sweet’s syndrome.

In Sweet’s syndrome, mature neutrophils (a type of white blood cell) infiltrate the tissues, but in histiocytoid Sweet’s syndrome, immature cells not mature neutrophils can be seen (mainly M2-like CD 163+macrophages) (Arima et al, 2015; Fernandez-Torres et al, 2014; Jo et al, 2012; Miller et al, 2015; Requena et al, 2005). These can be mistaken for histiocytes; immune cells that destroy foreign substances and help fight infection. Sometimes, real or ‘authentic histiocytes’ may also be present (Alegria-Landa et al, 2017).

What are the symptoms of histiocytoid Sweet’s syndrome?

The symptoms of histiocytoid Sweet’s syndrome and Sweet’s syndrome are the same. Read more here. 

How is it treated?

Histiocytoid Sweet’s syndrome is treated in the same way as Sweet’s syndrome. The most common treatment is steroid medication, e.g. prednisone, but other treatments have been used. In 2015, a female patient with histiocytoid Sweet’s syndrome was successfully treated with 50mg of azathioprine, daily (Miller et al, 2015). However, it is important to note that on rare occasions, azathioprine has been known to trigger Sweet’s syndrome.

Can histiocytoid Sweet’s syndrome be confused with other conditions?

Yes. Histiocytoid Sweet’s syndrome can be confused with the condition leukaemia cutis or inflammatory skin conditions that show lots of histiocytes in the tissues (Requena et al, 2005).

Diagnostic recommendations.

Due to histiocytoid Sweet’s syndrome association with cancer and blood disorders, it is recommended that:

  • A complete haematological assessment be given at diagnosis (Ghoufi et al, 2016).
  • Blood cell counts be monitored for at least 6 months after diagnosis.

Other information.

Very rarely, a patient may develop subcutaneous histiocytoid Sweet’s syndrome. The most recent case was reported in a patient with relapsed acute myeloblastic leukaemia (Lee et al, 2017).


Alegría-Landa, V., Rodríguez-Pinilla, S., Santos-Briz, A., Rodríguez-Peralto, J., Alegre, V., Cerroni, L., Kutzner, H. and Requena, L. (2017) Clinicopathologic, Immunohistochemical, and Molecular Features of Histiocytoid Sweet Syndrome. JAMA Dermatology, Mar 15 (PubMed).

Arima, Y., Namiki, T., Ueno, M., Kato, K., Tokoro, S., Takayama, K., Miura, K. and Yokozeki, H. (2015) Histiocytoid sweet syndrome: a novel association with relapsing polychondritis. The British Journal of Dermatology, Oct 16th (PubMed).

Fernandez-Torres, R., Castro, S., Moreno, A., Alvarez, R. and Fonseca, E. (2014) Subcutaneous histiocytoid sweet syndrome associated with crohn disease in an adolescent. Case Reports in Dermatological Medicine, March 26th (online).

Ghoufi, L., Ortonne, N., Ingen-Housz-Oro, S., Barhoumi, W., Begon, E., Haioun, C., Pautas, C., Beckerich, F., Robin, C., Wolkenstein, P., Cordonnier, C., Chosidow, O. and  Toma, A. (2016) Histiocytoid Sweet Syndrome Is More Frequently Associated With Myelodysplastic Syndromes Than the Classical Neutrophilic Variant: A Comparative Series of 62 Patients. Medicine (Baltimore), Apr;95(15):e3033 (PubMed).

Jo, M., Lim, Y., Shin, H., Choe, J., Seul, J. and Jang T. (2012) A Case Report of Sweet’s Syndrome with Parotitis. Archives of Plastic Surgery, Jan;39(1):59-62 (online).

Kato, K., Namiki, T., Tokoro, S., Miura, K. and Yokozeki, H. (2016) Histiocytoid Sweet syndrome with ophthalmologic involvements: A novel association with uveitis. The Journal of Dermatology, May 14 (PubMed).

Lee, J., Cornejo, K., Rork, J. Rothman, K. and Deng, A. (2017) Subcutaneous Histiocytoid Sweet Syndrome in a Patient With Relapsed Acute Myeloblastic Leukemia. The American Journal of Dermatopathology, Mar 9 (PubMed).

Miller, J., Lee, N. and Sami, N. (2015) Histiocytoid Sweet syndrome treated with azathioprine: a case report. Dermatology Online Journal, Jul; 21(7).

Requena, L., Kutzner, H., Palmedo, G., Pascual, M., Fernández-Herrera, J., Fraga, J., García-Díez, A. and Yus, E. (2005) Histiocytoid Sweet Syndrome:  A Dermal Infiltration of Immature Neutrophilic Granulocytes. JAMA Dermatology (online).

Shalaby, M., Riahi, R., Rosen, L. and Soine, E. (2016) Histiocytoid Sweet’s Syndrome in a Patient with Myelodysplastic Syndrome: Report and Review of the Literature. Dermatology Practical & Conceptual, Jan; 6(1): 9-13 (online).

Wick, M. and Bush, J. (2015) Cutaneous Histiocytoid Sweet Syndrome & its Relationship to Hematological Diseases. Journal of Cutaneous Pathology, Dec 23rd (PubMed).

© 2012-2017 Sweet’s Syndrome UK

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