Dysplastic gangliocytoma or Lhermitte-Duclos disease is a rare disorder characterized by a slowly progressive unilateral hamartomatous cerebellar tumor. It is associated with mutations of the phosphatase and tensin homolog (PTEN) gene and is one of the PTEN hamartoma tumor syndromes (PHTS). PHTS also includes Cowden syndrome, an autosomal dominant multi-system disorder that increases risk for benign and malignant neoplasms, and neurodevelopmental disorders.

A 65-year-old female presented with mild, occasional dizziness, lasting few seconds upon head movement. Examination showed mild dysmetria on left upper and lower limbs and mild intention tremor on left upper limb. The patient also exhibited papules, some hyperketarotic, on periorbital and retroauricular areas and nasal mucosa, oral papules and oral mucosa papillomas with a cobblestone appearance, and a hemangioma on the right shoulder and arm.

She was referred to our service and was being followed by other departments, which allowed the diagnosis of Cowden syndrome after evaluation of multiple hamartomatous lesions of the skin, uterus, breast, gastrointestinal tract, kidney and thyroid, and a histopathological exam of facial skin lesions showing a characteristic Trichilemmoma. She had an univitelline twin sister, who died at age 45 from a uterine neoplasia and had similar cutaneous polypoid lesions, which suggests a familial inheritance.

Magnetic resonance of brain revealed a left cerebellar lesion measuring 6,3x2,4cm, crossing the midline and partially occupying the right retrocerebellar cistern. The ipsilateral cerebellar cortex exhibited a salient "tiger stripe" appearance.

Lhermitte-Duclos is an extremely rare disorder that is strongly associated with Cowden syndrome. Recognition of the disease is of major importance, as PHTS has effects on almost all organ systems. A multidisciplinary treatment team is needed and a systematic work-up to detect or exclude concomitant malignancies should be made.