Histiocytoid Sweet's syndrome - unusual crusted lesions

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An atypical facial eruption in skin of color: A rare presentation of histiocytoid Sweet syndrome, 2024. jaadcasereports.org/article...

- Normally red to purple lesions in Sweet's syndrome.

- Doesn't disproportionately affect specific racial groups.

"Although SS does not have racial predilection, the clinical diagnosis often relies on identification of the classic erythematous to violaceous lesions, which as with our case, can be more challenging to identify in skin of color."

- Sweet's syndrome mainly affects face and upper body.

- Most patients have a fever. In this case, the patient had no fever.

- Unusual large crusted facial lesions.

"SS typically occurs on the head, neck, upper extremities, or trunk and is associated with constitutional symptoms such as fever; however, our patient was initially afebrile with predominately facial lesions. Additionally, the atypical presentation of vegetative plaques led to a very broad clinical differential."

- Diagnosed with histiocytoid Sweet's syndrome.

- Steroids only gave temporary relief.

- Condition successfully managed with dapsone.

"Corticosteroids are considered first-line therapy for HSS, and our patient was initially treated with corticosteroids with temporary relief. Alternative therapies have been used as initial treatment or after treatment failure and include potassium iodide, colchicine, indomethacin, dapsone, clofazimine, and cyclosporin. After failure with corticosteroid treatment, our patient was successfully treated with dapsone as monotherapy, which is typically considered second-line therapy."

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, and medications. In regards to the former, it normally occurs in association with a group of blood cancers called myelodysplastic syndromes. It has also developed secondary to infections and autoimmune conditions.

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). 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.