[Cowden's disease: a new paediatric observation].

We report on a paediatric observation of Cowden's disease in a 6-year-old child. Familial steroid-resistant nephrotic syndrome was associated to papulous and papillomatous lesions of gingiva and oral mucosa, multiple hamartoma of the back and of upper limbs, facial dysmorphism and follicular thyroid cancer. Thyroid cancer evolved favorably after surgical treatment, radioactive iodine and L-thyroxin supplementation. Nephrotic syndrome evolved to chronic renal insufficiency after 11 years. The early diagnosis of Cowden's disease, or multiple hamartoma syndrome, allows a careful monitoring of the patients who are facing the risk of cancer transformation, which is the principal complication of the condition.