Histiocytoid Sweet’s syndrome: a histological variant

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 has most commonly been associated with cancer (35-55% of cases), and medications (Morgado-Carrasco et al, 2018; Wick and Bush, 2015). In regards to the former, it normally occurs in association with a group of blood cancers called myelodysplastic syndromes (MDS) (Shalaby et al, 2016). It has also developed secondary to infections and autoimmune conditions (Morgado-Carrasco et al, 2018).

How many people have histiocytoid Sweet’s syndrome?

More than 70 cases of histiocytoid Sweet’s syndrome have been reported in medical literature (Arima et al, 2015; Kato et al, 2016; Macarini et al, 2016; Miller et al, 2015; Morgado-Carrasco et al, 2018; Shalaby et al, 2016; Watson et al, 2018; Yeom et al, 2017). By Oct 2017, only 5 cases had been in children (Yeom et al, 2017).

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 white blood cells called neutrophils accumulate in the tissues. In histiocytoid Sweet’s syndrome, immature myeloperoxidase-positive cells and 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). Myeloperoxidase is an enzyme that’s abundantly expressed in neutrophils.

The immature cells in histiocytoid Sweet’s syndrome 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. 

Skin lesions are the commonest symptom of Sweet’s syndrome, and there are different lesion types. In Sept/Oct 2016, the first case of histiocytoid Sweet’s syndrome with annular or ring-shaped lesions was reported in medical literature (Macarini et al, 2016). Initially, it was thought that this particular lesion type might be a symptom of another condition such as erythema multiforme, sarcoidosis, or granuloma annulare.

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’s important to note that on rare occasions, azathioprine has been reported to have triggered Sweet’s syndrome. When Sweet’s syndrome is triggered by medication, this is referred to as drug-induced Sweet’s syndrome. In 2018, the biologic drug, etanercept, was used to treat persistent Sweet’s syndrome in a 34-year-old woman (Watson et al, 2018).

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

Yes, histiocytoid Sweet’s syndrome can be confused with the conditions leukaemia cutis and Kikuchi-Fujoimoto disease (histiocytic necrotizing lymphadenitis), or other skin conditions that show histiocytes or histiocyte-like cells in the tissues (Macarini et al, 2016; Requena et al, 2005; Yeom et al, 2017).

Diagnostic recommendations.

Due to histiocytoid Sweet’s syndrome association with cancer and blood disorders, it’s 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.

In both histiocytoid Sweet’s syndrome and Sweet’s syndrome, biopsy can sometimes show other types of white blood cell, e.g. lymphocytes (Morgado-Carrasco et al, 2018; Sweet’s Syndrome UK, 2018).

Very rarely, a patient may develop subcutaneous histiocytoid Sweet’s syndrome. The most recent case was reported in a patient with relapsed acute myeloid 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 (PMC).

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).

Marcarini, R., Araujo, R., Nóbrega, M., Medeiros, K., Gripp, A. and Maceira, J. (2016) Histiocytoid Sweet’s syndrome presenting with annular erythematous plaques. Anais Brasileiros de Dermatologia, Sep-Oct;91(5 suppl 1):154-156 (PMC).

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

Morgado-Carrasco, D., Moreno-Rivera, N., Fusta-Novell, X., Garcia-Herrara, A., Carrera, C. and Puig, S. (2018) Histiocytoid Sweet’s syndrome during combined therapy with BRAF and MEK inhibitors for metastatic melanoma. Melanoma Research, Jun;28(3):256-257 (PubMed). Dabrafenib and trametinib.

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 (PMC).

Sweet’s Syndrome UK (2018) Myelodysplasia and Sweet’s syndrome.

Watson, I., Haugh, I., Gardner, A. and Menter, Martin Alan (2018) Histiocytoid Sweet syndrome successfully treated with etanercept. Baylor University Medical Center Proceedings, May 9 (Taylor & Francis Online).

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

Yeom, S., Ko, H., Moon, J.,  Kang, M., Byun, J., Choi, G. and Shin, J. (2017) Histiocytoid Sweet Syndrome in a Child without Underlying Systemic Disease. Annals of Dermatology, Oct;29(5):626-629 (PMC online).

2012-2018 Sweet’s Syndrome UK


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