1. In view of the above clinical course, is there a change in your working diagnosis concerning the patient’s left lower limb findings?
No.
2. In general, what type of pathological process do you think is involved in this case?
The most likely pathological process in this patient continues to be multiple mononeuropathies due to compression (aka: entrapment or pressure neuropathies). Other common causes of multiple mononeuropathies were not detected with extensive investigations, and decompression of three of her symptomatic nerves resulted in immediate improvement.
3. The findings in this case most likely represent a known neurologic syndrome. What is the name of this syndrome?
Hereditary Neuropathy with Pressure Palsies (HNPP).
HNPP is characterized by multiple, recurrent mononeuropathies, which are often provoked by trivial or even brief compression. The symptoms are usually painless numbness and/or weakness in the distribution of single peripheral nerves, which may last for weeks to months, but sometimes resolve more quickly.
HNPP is now known to be an autosomal dominant disorder caused by a deletion of the Peripheral Myelin Protein-22 (PMP22) gene on chromosome 17p11.2, such that the PMP22 protein is present at approximately half-normal levels.
Electrophysiological studies (EMG and NCS) are often abnormal, but the abnormalities may be subtle and minor. Nerve biopsy may show localized nerve sheath thickening with duplication of the myelin lamellae (so-called tomaculae).
This patient did not report a family history of multiple, recurrent mononeuropathies. This may simply have been due to a lack of awareness by family members or some other reason for an incomplete knowledge of family medical issues. Alternatively, her syndrome may have been caused by a spontaneous or de novo mutation involving the PMP22 gene. She was seen prior to the availability of genetic testing for this and similar conditions.
References:
1. Davies DM. Lancet 1954;264:266-268.
2. Earl CJ, Fullerton PM, Wakefield GS, Schutta HS. Q J Med 1964;33:481-498.
