A 54 year-old lady, previously diagnosed with acromegaly, presented with progressive visual loss despite biochemically inactive disease. The only previous treatment was surgical hypophysectomy 30 years ago.

She had bilateral severe concentric visual field loss, skin thickening, coarse facial features, macroglossia, and prominent brows and jaw. Perimetry demonstrated tunnel vision. There was no biochemical evidence of recurrent acromegaly. Pituitary MRI reported postsurgical changes only, without chiasmal compression. Two opthalmology reviews diagnosed Retinitis Pigmentosa as the cause of visual loss.

She subsequently developed progressive upper limb weakness, hypertonia, flexion contractures in the upper limbs, and bilateral median neuropathy. MRI of the spine showed multilevel cervical cord compression with diffuse thickening of spinal dural and ligamentous structures. Cervical spine decompression surgery and bilateral carpal tunnel release resulted in improvement in power and function.

Symptoms recurred 18 months later with new cervical cord compression on MRI. Lumbar canal stenosis had also occurred with decompression elsewhere. IGF1 levels remained below the normal age-matched reference range. GH suppressed to 0.1mIU/l with GTT. There were no new pituitary MRI changes.

Given the atypical pattern of visual loss and the recurrent episodes of severe multilevel nerve entrapment syndromes, hypertonia and joint contractures, yet without metabolic or proliferative features, and in the absence of biochemical acromegaly, we considered potential gain or loss of function mutations downstream of GH action within the GH/IGF1 axis.

Mucopolysaccarhidoses (MPS) are rare inherited lysosomal storage disorders targeting collagen degradation. Defective enzyme activity results in accumulation of glycosaminoglycans, with soft tissue overgrowth including visual, neurological and joint symptoms, mimicking the soft tissue and bony phenotype of acromegaly. Investigations confirmed the diagnosis of MPS-1:
- Elevated urinary glycosaminoglycans: 22.9 mg/mmol Cr (N<15.4)
15>- Low Alpha-l-Ioduronidase (IDUA) activity: 7 (N 15-134)
- A novel mutation in the IDUA gene

MPS-1 usually presents in childhood. To our knowledge, this patient is the oldest patient with MPS-1 to be diagnosed de novo in Australia. We discuss key similarities and differences in acromegaly versus MPS.