When it comes to differentiating between FD and DSC, it’s all about location, location, location.
Folliculitis decalvans (FD) and dissecting cellulitis (DSC) are both types of scarring alopecias, classified as subtypes of ‘neutrophilic’ scarring alopecia. Although they are classified as ‘neutrophilic’ scarring alopecia, biopsies of these two conditions show a mixture of neutrophils, lymphocytes, histiocytes and plasma cells. Typically, early lesions show neutrophils and later lesions show plasma cells and lymphocytes. Like all scarring alopecia, they may lead to permanent hair loss.
Figuring out whether a patient has FD or DSC can occasionally be challenging. Both clinical and histological features need to be considered. FD often presents in the mid scalp and crown with a red, itching and burning scalp with pustules. Hairs may or may not show tufting or grouping of follicles together to resemble doll’s hair or the bristles of a toothbrush. Dissecting cellulitis presents with tender boggy, deep seeded plaques that may exude pus when pressed.
The histology of FD and DSC can show similarities. However, the inflammation (and scarring) in DSC is fundamentally a deeper process than FD. Inflammation in DSC involves the reticular dermis and subcutis and inflammation in FD involves the upper and mid dermis. Other histological features are also important including the presence of sinus tracts in DSC. However, the recognition of the differences in the location of the inflammation and scarring (upper vs lower)is important for pathologists who evaluate biopsies of these two conditions.
Article orginally posted at donovanmedical.com