[Acne flare on isotretinoin: A pointer to diagnosis of hidradenitis suppurativa].

BACKGROUND

Isotretinoin is the most potent treatment for acne but paradoxical flares can occur. HS lesions of the face may be mistaken for acne. We report on 4 patients in whom an "acne" flare on isotretinoin led to the correct diagnosis of HS.

PATIENTS AND METHODS

Four young male patients aged 15 to 28 years were referred to us because of an acne flare on isotretinoin. Three of them had clinical features considered unusual in acne : involvement of the nape of the neck (2), retroauricular cysts (2), a rope-like pre-sternal lesion (1), a large bag-like sinus on the face (1), large deep depressed U-type scars on the back (3). Questioning revealed that all three had previously experienced several attacks of inflammatory nodules in the axillae and/or inguinal folds; they had not mentioned these lesions since they seemed so minor. The fourth patient had lesions typical of HS comprising nodules, sinus, rope-like hypertrophic scars on the face mistaken for acne, epidermal cysts on the scrotum and pubic folliculitis. Treatment with systemic antibiotics resulted in regression of lesions in all 4 patients.

DISCUSSION

An acne flare on isotretinoin requires investigations with a view to potential diagnosis of HS. Patients presenting "acne" and atypical features such as involvement of the neck, large U scars and cord-like structures should be questioned about the presence of nodules in the axillae and groin since patients with mild HS may not spontaneously acknowledge such typical symptoms.