Investigators at the Massachusetts General Hospital, Boston, MA, tested the hypothesis that acquired small-fiber polyneuropathy (SFPN) contributes to unexplained widespread pain syndromes in children and adolescents. Medical records of 41 consecutive patients were analyzed for objective diagnostic test data for SFPN. These included skin biopsy, nerve biopsy, and autonomic function testing, plus histories, symptoms and signs, and treatments. Healthy matched volunteers acted as normal controls for SFPN tests.
In this polyethnic patient sample, age at illness onset averaged 12.3 +/- 5.7 years; 73% were female, 68% chronically disabled, and 68% had been hospitalized. Objective diagnostic test results were definite for SFPN in 59%, probable in 17%, and possible in 22%. Only 1 had normal SFPN test results. Somatic complaints other than pain were reported in 98% patients and were consistent with SFPN dysautonomia (90% cardiovascular, 82% gastrointestinal, and 34% urological). Chronic fatigue was reported in 83% and chronic headache in 63%. Neurological examinations identified reduced sensation in 68% and vasomotor abnormalities in 55%, including erythromelalgia in 23%. Tests for causality of pain revealed only a history of autoimmune disease elicited in 33% and serologic markers of disordered immunity in 89%. Treatment with corticosteroids and/or IV immunoglobulin benefited 80% of patients (12/15), both objectively and subjectively. 
COMMENT. Chronic, diffuse pain syndromes involving small nonmyelinated-C fiber peripheral nerves, especially in the extremities and feet, and the autonomic nervous system are a well-known but little understood disorder of the elderly, often referred to as “burning feet syndrome.” The cause may be nutritional, vitamin B deficiencies, diabetes, hypothyroidism, spinal stenosis, or genetic , but often idiopathic . SFPN in children is rarely reported. It appears to be an autoimmune disorder, but symptoms of dysesthesia and hyperesthesia are also encountered in children with ADHD and PDD, associated with an abnormal microarray, deletion 17p12 (Personal case report). 
Diagnostic testing for small fiber neuropathy
SFPN is characterized by loss of sensation (thermal and pinprick hypoesthesia) and positive sensory symptoms (burning pain, allodynia, hyperalgesia). Clinical neurological examination and routine neurophysiologic tests are often insufficiently sensitive, but skin biopsy and recent availability of normative reference values are of proven value in the diagnosis of damaged small nerve fibers . In an earlier study of 486 patients with SFPN, skin biopsy had a diagnostic efficiency of 88.4%, clinical examination of 54.6% and quantitative sensory testing of 46.9%.