The often forgotten element: a key differential diagnosis for eczema, allergy, or infection

A five month old ex-26 week premature infant presented to the emergency department with a five week history of a rash, irritability, and diarrhoea. The rash consisted of erythematous, scaly, crusted skin lesions involving the head (fig 1), neck, perineal, and genital area. The infant was exclusively breastfed and had a history of chronic lung disease of prematurity. He had recently received a diagnosis of bronchiolitis and had been hospitalised in the paediatric intensive care unit for one week. He had a family history of psoriasis in a paternal aunt.

A diagnosis of superinfected eczema was suspected so systemic antibiotics were started resulting in initial improvement of the symptoms, but the skin lesions subsequently worsened. The infant had no response to various other treatments such as dairy exclusion from the mother’s diet for suspected cow’s milk protein allergy, topical emollients and steroids (eczema), topical miconazole, oral nystatin (fungal infection), oral aciclovir (viral infection), repeated oral co-amoxiclav (impetigo and cellulitis). He was receiving prophylactic iron and multivitamins, phosphate supplements, and alginic acid as regular medication.

The results of repeated blood cultures and skin swabs for bacterial and fungal culture were negative, as were skin swab polymerase chain reaction tests for herpes viruses (herpes simplex viruses 1 and 2, varicella zoster virus). Erythrocyte sedimentation rate and C reactive protein were normal, full blood count unremarkable except for a mild thrombophilia (778 cells 10⁹/L, normal range 150-350 cells 10⁹/L). Alkaline phosphatase levels were low (105 U/L, normal …