Coexistence of steatocystoma multiplex and hidradenitis suppurativa: Assessment of this unique association by means of ultrasonography and Color Doppler

Background: Steatocystoma multiplex (SM) is an uncommon skin disease manifesting as multiple sebum-containing cysts arising in pilosebaceous unit-rich body areas. Hidradenitis suppurativa (HS) is a debilitating chronic inflammatory disease affecting the apocrine gland-bearing skin and presenting with both pseudocystic and inflammatory nodules, abscesses and fistulas. Considering that genetics has been reported to play a role in both entities, the albeit rare association between them suggests a shared genetic background. Although histology remains the gold standard for the diagnosis of SM, ultrasonography can be an useful diagnostic tool. This method is largely used in combination with Color Doppler for assessing disease severity in HS. Materials and Methods: We report three cases of coexisting SM and HS and describe the ultrasonography and Color Doppler features of the two entities. Results: SM lesions appeared on ultrasonography as hypoechoic nodules with well-defined hyperechoic borders and posterior acoustic enhancement, in the absence of Color Doppler signal. HS lesions had the ultrasonographic features of the fistulas, abscesses and pseudocystic nodules, some of which including hair fragments, with an intense Color Doppler signal within or around inflamed lesions. Conclusion: The combination of ultrasonography and Color Doppler proved to be a reliable instrument for differentiating between SM and HS lesions, particularly distinguishing HS pseudocystic nodules from true cysts of SM.