Descriptive epidemiology of a rare neuropathic syndrome in Navajo children.

This study is an attempt to determine the incidence and geographic distribution of Navajo neuropathy on the Navajo Reservation. To that end, the researchers established an epidemiologic surveillance system and attempted to identify all cases occurring since 1960 A definite case of Navajo Neuropathy was defined as a patient who experienced at least four of the following signs and symptoms prior to the age of 10, and showed no alternative diagnosis: 1) Sensory neuropathy demonstrated by physical exam, acral mutilation, or sural nerve biopsy; 2) Motor neuropathy demonstrated by physical exam, denervation on electromyography, or delayed motor nerve conduction velocity; 3) Corneal ulceration and/or scarring; 4) Liver derangement defined as sero-negative hepatitis, chronic active hepatitis, fulminant liver failure, Reye syndrome-like episode or cirrhosis; and 5) At least one documented metabolic or infectious derangement, including short stature (below 5th percentile), inadequate weight gain (below 5th percentile), delayed puberty (beyond age 14), or systemic infections (at least one episode of sepsis, meningitis, disseminated viral infection, pyelonephritis, or pneumonia requiring hospitalization). A case was considered definite with four signs and probable if the patient displayed two signs. Demographic, environmental, and family histories were obtained from families of definite cases through home visits conducted by the researchers. Standard descriptive statistical techniques were used. Epidemiologic surveillance resulted in the identification of nine previously unidentified cases. In all, twenty definite cases and four probable cases were diagnosed. The average annual incidence of definite and probable cases on the Navajo Reservation from 1972 to 1986 was 20 cases/ 100,000 births. The 24 identified cases were from 13 Navajo families. Six of those families had more than one affected sibling. Extensive family histories revealed common ancestors in four of the thirteen families. No common environmental factors were discovered in families of definite cases. It may be years before the etiology of the pathogenesis of Navajo neuropathy is discovered. In the interim, medical intervention is aimed at preventing acral mutilation, contractures and corneal scarring, and providing nutritional support. Patients should have periodic serum albumin levels and coagulation studies to evaluate liver function. Routine follow-up should be conducted by Pediatric Neurologists, Ophthalmologists and Orthopedic Surgeons.