Peripheral neuropathy in diabetes: it's not always what it looks like

Hereditary Neuropathy with liability to Pressure Palsies (HNPP) is an autosomal dominant neuropathy, associated with deletion of the Peripheral Myelin Protein-22 (PMP-22) gene, causing recurrent painless palsies with age of onset between 10 and 30 years old. Only a few cases of Type 2 Diabetes and HNPP have been described and the coexistence of HNPP and Type 1 diabetes has never been reported.

A 54-year old man with a history of Type 1 diabetes, managed with continuous subcutaneous insulin infusion (CSII), presented with deterioration of long-standing motor and sensory symptoms, previously attributed to golfer's elbow, diabetic neuropathy and spinal degenerative disease. He had multilevel severe spine degenerative changes and L4/L5 and L5/S1 root impingements with a L4/L5 discectomy performed when he was 25 years old. On physical examination he had normal power and distal hypoaesthesia of the digits and plantar aspect of the feet. Investigations revealed normal full blood count, liver and renal function, electrolytes, vitamin B12 and serum folate. He suffered from primary hypothyroidism and thyroid function tests indicated adequate levothyroxine replacement. Nerve conduction studies revealed a generalized demyelinating sensorimotor neuropathy, with more severe involvement of nerves over entrapment sites. Further history that his father suffered from episodes of weakness and numbness was elicited. Genetic analysis revealed one copy of the PMP22 gene at 17p11.2 confirming the diagnosis of HNPP.

In people with diabetes the evaluation of peripheral neuropathy should include a careful history, a comprehensive physical examination, blood tests and in some cases nerve conduction studies and genetic testing.