Off-label use of low dose rituximab may be a valuable option for management of  pemphigus, experience at a Victorian hospital suggests.

Clinicians at the Department of Dermatology, Royal Melbourne Hospital have described how some patients have achieved control of pemphigus within a month after receiving ultra-low doses of rituximab.

In their report, published in the British Journal of Dermatology, they say the rationale for using rituximab comes from its role binding to the CD-20 antigen expressed on B-cell lymphocytes, which produced the destructive antibodies that cause pemphigus

And in pemphigus treatment depletion of B-cell lymphocytes can be achieved with only a fraction of the haematological dose, they note.

While previous rituximab protocols for pemphigus have used two x 1000mg and two x 500mg doses, the Melbourne clinicians report a case series of eight patients who received two infusions of 200mg rituximab 14 days apart.

In this group of patients, six had mucocutaneous disease and two had mucosal dominant disease. The reasons for using rituximab included recalcitrant disease or contraindications to traditional immunosuppressants.

Dr Laura Scardamaglia and colleagues report that all the paients reached an early end point of disease control, with one achieving disease control on day 24, while the longest time to achieve an early end point was 111 days.

They note that  two patients achieved partial remission on minimal therapy, two achieved complete remission on minimal therapy, and two achieved complete remission off therapy.

While there was a 20% relpase rate in the small group of patients, the study authors note that six out of eight patients saw a reduction in PDAI at 6 months with no increase in adjuvant therapy, while all but one of the eight patients showed a reduction for PDAI score at 12 months, and a mean improvement from baseline of 90%.

“The reductions in PDAI are clinically significant given the impact blistering skin conditions have on quality of life,” they wrote.

Most patients were also were able to decrease the daily prednisolone dose, they added.

With no serious adverse events reported, they concluded that the ultra-low dose rituximab protocol “may be an efficacious and safe option in patients with mild pemphigus disease in conjunction with more traditional adjuvants, and offers an alternative to the 500mg and 1000mg dosing protocols.”