We present the case of a 12-month-old boy presenting in February 2014 with widespread soft tissue nodules that had progressed over 5 months. They were not painful or itchy and there were no associated symptoms. He had continued to gain weight and had remained systemically well.

He had widespread subcutaneous and firm nodules over his scalp, forehead, trunk, back, abdominal wall and scrotum. They were non-tender and had no overlying skin changes. He was pale but systemic examination was otherwise normal. There was no significant lymphadenopathy or hepatosplenomegaly.

Blood tests confirmed normocytic, hypochromic anaemia (Hb 69 g/L), slightly low white cell count (5.5 × 10⁹/L) and normal platelet count (198 × 10⁹/L). Over the following week the blood count deteriorated with progressive anaemia and leucopenia with an increasing blast cell population. Tissue biopsy and bone marrow aspirate confirmed a diagnosis of pre-B cell acute lymphoblastic leukaemia (ALL) with mixed-lineage leukaemia (MLL) gene rearrangement.

Cutaneous leukaemia (leukaemia cutis) is a rare presentation of ALL signifying neoplastic infiltration of the skin. The appearance of skin lesions is variable and can manifest in different leukaemia subtypes (most commonly seen in acute myeloid leukaemia and in neonates). Occasionally it may be the only clinical sign of leukaemia but is invariably felt to be a poor prognostic sign.

This case describes an unusual presentation of childhood leukaemia, highlighting the importance of early skin biopsy in unusual cutaneous lesions. To our knowledge it is the first case of cutaneous leukaemia in a child with pre-B ALL with an MLL gene rearrangement.