A rash that's more than skin deep.

A 6 week old baby presented with petechiae and erythematous macules over the periorbital and perioral areas, spreading to the forehead and malar areas (fig 1). She had been delivered vaginally at 36 weeks’ gestation and was small for gestational age, with no hepatosplenomegaly. Serology tests for toxoplasma, rubella, cytomegalovirus, and herpes simplex were negative. The baby had transient neonatal thrombocytopenia secondary to maternal chronic immune mediated thrombocytopenia (also known as immune thrombocytopenic purpura).Fig 1 Periorbital and perioral petechiae and erythematous maculesGiven the distribution of the rash and the mother’s history of immune thrombocytopenia, an auto-antibody profile was performed. This showed positive speckled antinuclear antibodies titre u003e1/800 (normal range u003c1/100), positive anti-double stranded DNA antibody levels 65.11 IU (u003c25 IU), and presence of extractable nuclear antigen antibodies anti Ro/SSA, La/SSB, Sm, RNP, Scl70, and Jo-1, with index values of 5.8, 6.1, 5.2, 4.8, 4.0, and 4.7, respectively (u003c1.0). Complement levels were C3 0.42 g/L (0.51–1.60 g/L) and C4 u003c0.03 g/L (0.07–0.30 g/L). Full blood count showed a haemoglobin level of 8.7 g/dL (9.0-14.0 g/dL), total white blood cell count 10.74×109/L (5.00-15.00×109/L) and platelet count 144×109/L (150-450×109/L). Liver and renal function tests were normal. The child was well, and the lesions resolved by the time she was 6 months old (fig 2).Fig 2 Resolution of rash at 6 months, with dermal atrophy at the sides of the face (arrows)