Systemic immunosuppressant therapy in childhood

The indications for systemic immunosuppressant therapy are much the same in children as in adults. Perhaps the most important difference is the need in a child to consider more carefully the patient's likely future therapy requirements. This need reflects a justifiable anxiety concerning the longer‐term toxicity associated with some of these drugs. It is obvious that special attention should be paid to the dosage regimens that are appropriate in children. However, otherwise the principles of treatment are essentially the same as in adults. This talk will focus on the use of azathioprine in atopic eczema, methotrexate in psoriasis and linear morphoea, and intravenous methylprednisolone in severe muco‐cutancous erythema multiforme and toxic epidermal necrolysis. The value of azathioprine as a treatment for severe childhood eczema was greatly increased by the elucidation of the metabolic pathways for this drug, and by the development of an assay for thiopurine methyl transferase to allow detection of those at greatest risk of myelosuppression. We now treat children with normal TPMT levels with 3 mg/kg per day with gratifying therapeutic response and limited requirement for monitoring of blood counts and liver function. More recently we have successfully treated TPMTHL heterozygotes with doses of around 1.5 mg/kg per day. We now consider azathioprine as superior to cyclosporin as a systemic therapy for atopic eczema. The value of methotrexate in adults with plaque psoriasis and generalized pustular psoriasis is well established. It is equally useful in children with these disorders, and the most appropriate dosage appears to be in the region of 0.3–0.4 mg/kg as a single weekly dose. Children generally tolerate oral therapy well. Methotrexate also appears helpful in arresting the progression of linear morphoea, both in the case of coup de sabre lesions and progressive hemi‐facial atrophy, and in limb lesions that are interfering with joint mobility or are causing profound lipoatrophy. Intravenous methylprednisolone appears to be of value in several acute dermatoses in childhood, but is most commonly used at Great Ormond Street Hospital in the hope of arresting progression of severe muco‐cutaneous erythema multiforme and toxic epidermal necrolysis. Various dose regimens are used in children, but in our unit we use a dose of 20–30 mg/kg per day, up to a maximum of 500 mg, for 3 successive days. Each dose is given over period of 2 h with frequent monitoring of vital signs, particularly blood pressure.