Sometimes, Sweet’s syndrome can occur in an unusual form. This is known as a disease variant.
What is subcutaneous Sweet’s syndrome?
Subcutaneous Sweet’s syndrome, otherwise known as Sweet’s panniculitis, is a rare form of Sweet’s syndrome where the subcutaneous, i.e. fatty tissue under the skin becomes inflamed. On occasion, both the skin and fatty tissue can be affected. When it develops secondary to another condition, it is most commonly associated with a group of blood disorders called myeloid disorders, but can also occur in association with other blood disorders (chronic lymphocytic leukaemia), health conditions and medication (Fernandez-Torres et al, 2014; Hashemi et al, 2016; Kim et al, 2010; Wang et al, 2014).
What does it look like?
Most of the time, the skin lesions caused by subcutaneous Sweet’s syndrome look like coin-sized red areas or red circular bumps that appear under the skin. However, they can sometimes look different. These lesions may be tender or painful, and most commonly appear on the extremities, e.g. arms, legs, ankles, or soles of the feet, but can develop on any part of the body (Fernandez-Torres et al, 2014; Kim et al, 2010; Wang et al, 2014). When the inflammation has settled, a temporary or permanent depression may be left in the skin.
Can subcutaneous Sweet’s syndrome be confused with other conditions?
Yes. Subcutaneous Sweet’s syndrome can sometimes be confused with infectious panniculitis, cellulitis, but more commonly, the skin condition erythema nodosum.
How is it diagnosed?
What kind of biopsy is needed?
An incisional and not a punch biopsy is often needed to accurately diagnose subcutaneous Sweet’s syndrome. This is because a punch biopsy does not always provide an adequate sample as it does not penetrate deeply enough.
Will I only need one biopsy?
You may need more than one biopsy, and if possible, biopsies should be taken from different lesions on different parts of the body. This is because Sweet’s syndrome or subcutaneous Sweet’s syndrome can appear at the same time as erythema nodosum or one condition can appear after the other (Kaur et al, 2015; Qiao et al, 2015). However, when this happens it has not been determined whether or not this is always a true erythema nodosum or an erythema nodosum-like manifestation of Sweet’s syndrome (Kaur et al, 2015).
What will the biopsy show?
The biopsy will normally show neutrophil/neutrophil-rich lobular or septal panniculitis without vasculitis, i.e. lots of white blood cells called neutrophils and no inflammation of the vessels in the fatty tissue under the skin
How is it treated?
Subcutaneous Sweet’s syndrome is treated in the same way as other forms of Sweet’s syndrome. In July 2016, the biological therapy, adalimumab (Humira), was used to successfully treat persistent subcutaneous Sweet’s syndrome (Agarwal et al. 2016). Read more about treatment here.
Very rarely, a patient may develop subcutaneous histiocytoid Sweet’s syndrome (Fernandez-Torres et al, 2014). Read more here.
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).
Hashemi, S., Fazeli , S., Vahedi, A. and Golabchifard, R. (2016) Rituximab for refractory subcutaneous Sweet’s syndrome in chronic lymphocytic leukemia: A case report. Molecular and Clinical Oncology, Mar;4(3):436-440 (online).
Qiao, J., Wang, Y., Bai, J., Wu, Y. and Fang, H. (2015) Concurrence of Sweet’s Syndrome, Pathergy Phenomenon and Erythema Nodosum-Like Lesions. Anais Brasileiros de Dermatologia, Mar-Apr;90(2):237-9 (online).
Wang, H., Huang, Y., Chen, W. and Chiang Y. (2014) Subcutaneous Sweet syndrome associated with disseminated nontuberculous mycobacterial infection leading to the diagnosis of adult-onset immunodeficiency. Journal of the American Academy of Dermatology, Jul;71(1):e20-2 (online).
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