Objective The aim of this study was to report the earliest age of diagnosis of common clinical findings in children with PTEN hamartoma tumour syndrome (PHTS).

Design Medical records of children with PHTS were reviewed; data included growth measurements, presence or absence of specific clinical manifestations and tumours, and documented ages of diagnosis.

Setting Children with PHTS evaluated at Boston Children's Hospital from 1996 to 2011.

Patients The cohort included 34 children diagnosed with PHTS via genetic testing, under the age of 21 years. Of these, 23 were male and 11 female. The mean age at their last documented clinical evaluation was 13.6 years. The mean follow-up time was 7.5 years.

Results Macrocephaly and developmental/intellectual disability were consistent findings. Pigmented penile macules were noted in all males examined for this finding. Thyroid nodules, found in half the children screened with ultrasound, were diagnosed as early as at 5 years of age. Thyroid carcinoma, identified in 12% of the children in this cohort, was diagnosed as early as at 7 years of age. Other tumours included renal cell carcinoma diagnosed at 11 years of age and granulosa cell tumour of the ovary and colonic ganglioneuroma, each diagnosed at 16 years of age.

Conclusions Specific clinical findings and tumours are characteristic in children with PHTS. Tumour development occurs in young children with this condition, which necessitates early surveillance, especially of the thyroid.