Spontaneous remission in congenital leukemia is not related to (mosaic) trisomy 21: case presentation and literature review.

Congenital leukemia is seldomly diagnosed. Cases should be differentiated from transient leukemoid reaction, which is noted in Down syndrome. Outcome in congenital leukemia is poor, but spontaneous remissions have been described. The authors report on a female neonate with myeloid leukemia of the skin; no blood and bone marrow involvement was noted. Constitutional 47, XX, + 21 was excluded. In situ hybridization on a paraffin-embedded skin biopsy sample did not show trisomy 21 in the leukemia lesions. No antileukemia therapy was given. During follow-up, small nodules (diameter up to 3 mm) on the soles of both feet came and went over a 3-month period. The child is now 3.5 years old and well. To date, 18 cases of congenital leukemia showing spontaneous remission have been described in the literature, almost exclusively myeloid leukemia (FAB M4 and M5). Congenital leukemia confined to the skin was described in only 4 cases. On follow-up, 6 cases relapsed; only one of them initially had skin involvement only. The data from this patient and literature indicate that cytostatic treatment should start only if the malignancy interferes with vital parameters. In case of relapse or progression, initial postponement of chemotherapy in these frail neonates will result in less toxicity and probably a better survival.