POSTERIOR STALK INTERRUPTION SYNDROME

A PECULIAR PRESENTATION OF AN UNCOMMON DISEASE

Abstract

INTRODUCTION/BACKGROUND
Posterior stalk interruption syndrome (PSIS) is a rare anatomical congenital anomaly that is characterised by a radiological triad of a thin or interrupted pituitary stalk, an absent or ectopic posterior lobe and anterior lobe hypoplasia or aplasia. Patients typically manifest with anterior pituitary hormone deficiencies at varying ages of presentation ranging from infancy to early adulthood.

CASE
We present a 15-year-old female who was initially referred for thrombocytopenia and hepatosplenomegaly. Further evaluation revealed that she also had short stature and primary amenorrhea. Antenatal history was unremarkable with no reported obstetrics complications. Clinical examination is consistent with Tanner Stage 1 with a height measuring below the third centile for her age. Initial work-up with peripheral blood, iron studies and haemoglobin analysis confirmed true thrombocytopenia and ruled out haemoglobinopathies. Screening of the anterior pituitary hormone profile revealed that she had hypothyroidism, hypocortisolism, growth hormone deficiency, low gonadotropins levels with normal prolactin. MRI demonstrated a small anterior pituitary measuring 0.4 cm, with an ectopic posterior lobe and the infundibulum was not visualised. Her presentation, complemented with the biochemical and radiological findings confirmed a diagnosis of PSIS. She was started on hormonal replacement therapy.

CONCLUSION
PSIS occurs in about 0.5/100,000 births. The pathogenesis is largely unknown, though genetic factors and obstetric trauma are considered potential contributors. Common presentation includes short stature and delayed puberty. A combination of clinical assessment and biochemical tests is required to form a suspicion with MRI as the confirmatory test, differentiating PSIS from other pituitary pathologies. Treatment involves replacing the deficient hormones.