isotretinoin and antibiotic is not suitable for treatment of the acne patient. Please try Zinc and high dose niacin(≥20mg/kg/d, 300~500mg qid, gradually increase to high dose) to treat your patient for at least 3 month. Patients with Down syndrome frequently associated with hyperdyslipidemia, therefore niacin should be in very high dose. Acne patient will improved after one month of treatment.
There is no harm in treating a patient with Downs syndrome having acne vulgaris with isotretenoin. The indication should be gr3/4 acne and failure of treatment with topicals. Zinc and niacin will be of no use in acne conglobata
Agree with above. No worries about the risk in a patient with downs syndrome who is otherwise well. I would not hesitate because this may be the only effective therapy to reduce scarring.