A 3-month-old boy presented with erythroderma. He had been born at term following an uncomplicated pregnancy; his parents were consanguineous. At the age of 2 weeks, he developed a widespread erythematous scaly rash, and from the age of 4 weeks, he developed recurrent respiratory tract infections and intermittent diarrhoea. By the age of 3 months, his weight had dropped dramatically to the 0.4% centile, he was failing to thrive, had a hepatosplenomegaly and lymphadenopathy of unknown origin and required admission to the paediatric high dependency unit.Physical examination revealed a nonpruritic erythematous scaly eruption, which extended to cover the entire body surface area (Fig. 1) and widespread scale on the scalp with alopecia (Fig. 2).Laboratory investigations revealed hypogammaglobulinaemia [IgG 0.56 g/L (normal range 2.4-8.8 g/L), IgA < 0.03 g/L (0.10-0.50 g/L), IgM 0.06 g/L (0.20-1.00 g/L)], while IgE was elevated [782 kU/L (0-10.9 kU/L)]. Full blood count revealed eosinophilia [2.99 9 10 9 /L (0.1-1.0 9 10 9 /L)], lymphocyte counts were normal and cell subsets identified no B cells and normal T cells. Liver function tests were deranged [gammaglutamyl transferase 752 IU/L (1-55 IU/L), alkaline phosphate 429 IU/L (126-524 IU/L), aspartate aminotransferase 110 IU/L (10-77 IU/L]) with an elevated international normalized ratio of 1.83 (normal level 1).
Histopathological findingsA 3-mm punch biopsy was taken from the abdomen and at low power (Fig. 3a), compact hyperkeratosis with minimal parakeratosis was seen. At high power (Fig. 3b), a florid interface dermatitis, comprising lymphocytes, satellite cell necrosis and apoptotic keratinocytes, was identified, resembling a graft-versushost disease (GVHD) picture. Few eosinophils were seen. There were no features of ichthyosis or eczema.