Successful management of pemphigus foliaceus with mycophenolate mofetil as a steroid-sparing agent in a cat with corticosteroid-associated congestive heart failure.

Case summary: A 5-year-old British Shorthair cat was diagnosed with pemphigus foliaceus (PF) and was initially treated with methylprednisolone (0.7 mg/kg q12h), which possibly resulted in congestive heart failure (CHF). Treatment was switched to dexamethasone (0.09 mg/kg q24h) and mycophenolate mofetil (MMF) (10 mg/kg q12h) was added as a steroid-sparing agent. Although dexamethasone was slowly tapered off, MMF alone successfully maintained PF in remission. After 15 weeks of treatment, blood tests showed neutropenia and thrombocytopaenia. MMF dose reduction (10 mg/kg q24h) resulted in the normalisation of haematological parameters, although a mild flare of PF occurred. The reintroduction of dexamethasone (0.09 mg/kg twice weekly) rapidly restored disease control. MMF (10 mg/kg q24h) and dexamethasone (0.045 mg/kg twice weekly) were continued as maintenance therapy. After 36 weeks, the cat remained in clinical remission without further complications. Relevance and novel information: To the best of the authors' knowledge, this is the first case report to describe the use of MMF in a cat with PF. MMF was well tolerated and it was able to manage clinical signs even after the discontinuation of corticosteroids. Since mild and reversible haematological abnormalities were observed, careful monitoring during MMF administration is recommended. In this case, MMF dose reductions led to flares requiring a temporary reintroduction of corticosteroids to maintain disease control. MMF could be useful as an alternative treatment in cats affected by comorbidities where corticosteroid monotherapy would pose risks.