Cutaneous involvement in an 8-year-old boy with Ras-associated autoimmune leucoproliferative disorder (RALD).

Ras-associated autoimmune leucoproliferative disorder (RALD) is a nonmalignant syndrome associated with somatic KRAS mutations. We report a patient with RALD and cutaneous lesions, the first such case reported, to our knowledge. An 8-year-old boy presented with erythematous plaques on his face and body, along with lymphadenopathies and spleen enlargement without systemic symptoms. An increased number of monocytes were found in skin biopsy, peripheral blood and bone marrow (BM). Juvenile myelomonocytic leukaemia (JMML) was suspected. Genetic study using peripheral blood showed no mutations in the KRAS, PTPN11, NRAS, CBL or BCR-ABL genes, but bone marrow analysis revealed a mutation (p-G12S/c.34 G>A) in the KRAS gene. The karyotype was normal. No KRAS mutations were found using molecular analysis of saliva. The diagnosis of RALD was proposed. The differential diagnosis between RALD and JMML is challenging because there are no established criteria to differentiate between them. The clinical course of RALD is uncertain, so long-term follow-up is recommended.