Amyotrophy, Hereditary Neuralgic

A number sign (#) is used with this entry because of evidence that hereditary neuralgic amyotrophy (HNA) is caused by heterozygous mutation in the SEPT9 gene (604061) on chromosome 17q25.

Description

Hereditary neuralgic amyotrophy (HNA) is an autosomal dominant form of recurrent focal neuropathy characterized clinically by acute, recurrent episodes of brachial plexus neuropathy with muscle weakness and atrophy preceded by severe pain in the affected arm.

Clinical Features

Taylor (1960) studied a family in which 5 generations were affected by single or recurrent attacks of mononeuritis with a particular predilection for proximal brachial localization. The trait behaved as an autosomal dominant with high penetrance. Clinically, the picture closely resembled serum neuritis, suggesting that the fundamental defect might be a genetic susceptibility to 'hyperergic reactions.' The authors noted that episodes may be triggered by periods of physical or emotional stress and pregnancy.

In 7 patients from 2 unrelated families, Jacob et al. (1961) observed 14 similar episodes of recurrent brachial neuritis or mononeuritis multiplex. Attacks were featured by incapacitating pain, weakness, wasting, depression of reflexes, and sensory loss. The legs were involved only in instances of severe arm involvement. Narrow face with close-set eyes was a feature. Gardner and Maloney (1968) emphasized ocular hypotelorism and reported associated syndactyly in this disorder.

Guillozet and Mercer (1973) described 4 cases of recurrent brachial neuropathy in 3 generations of a family. These patients showed recurrent attacks of pain, weakness, and sometimes muscle-wasting in the arms and hands. These attacks generally were known to remit gradually, sometimes leaving residual weakness or muscular atrophy. Although the brachial plexus is primarily involved in this condition, the lower cranial nerves and the sympathetic nervous system may also be affected.

Airaksinen et al. (1985) reported a Finnish pedigree in which 13 members in 3 generations were affected with recurrent brachial plexus neuropathy. The first episode usually occurred in childhood after a mild infection. Affected patients had hypotelorism, small palpebral fissures, and a small mouth. Despite limitation of symptoms to the upper limbs, sural nerve biopsy in 1 patient showed tomaculous neuropathy. The authors interpreted this finding as indicating a generalized abnormality of Schwann cells predisposing the patients to recurrent palsies precipitated by exogenous factors. Phillips (1986) pointed out that isolated long thoracic nerve palsy causing weakness of the serratus anterior muscle and winging of the scapula, while usually traumatic in origin, can be a major manifestation of familial brachial plexus neuropathy. He studied the disorder in 4 persons in 3 generations of a family. There was male-to-male transmission. In 1 person, facial paresis was also present.

Thomas and Ormerod (1993) described a family in which 4 members over 2 generations were affected by neuralgic amyotrophy. A brother and sister were described in detail; another brother and the father were described briefly and not examined. At 19 years of age, the sister had developed pain around her right shoulder which lasted for about 2 days and was followed by difficulty in elevating the right arm and winging of the right scapula. This resolved over the following 5 months. At the age of 20 years, she began to suffer from episodes of pain, usually in the limbs, which lasted for a few days and were followed by areas of sensory loss. At the age of 31, toward the end of a pregnancy, she developed severe pain over the outer aspect of the right upper thigh which she maintained was worse than her subsequent labor pains. This was followed by cutaneous sensory loss in the same area. A brother developed painful winged scapula at age 25 with subsequent recovery. The father of the 3 sibs experienced a painful winged scapula which developed 2 weeks after an injection of antitetanus serum. Although the pain subsided, muscle strength was recovered only partially. There were no dysmorphic features in the family. Thomas and Ormerod (1993) pointed out similarities to the migrant sensory neuritis of Wartenberg (Matthews and Esiri, 1983).

Stogbauer et al. (1997) noted that the disorder is characterized clinically by episodes of brachial plexus neuropathy with muscle weakness and atrophy, as well as sensory disturbances. In almost all cases, the onset of muscle weakness is preceded by severe pain in the affected arm. The age of onset of the disease is in the second and third decade of life, although children in the first decade may be affected. Recovery is usually complete and begins weeks to months after the onset of symptoms. Recurrent episodes affect the same as well as the opposite arm. From electrophysiologic studies there is no evidence for a generalized neuropathy in HNA. Histologically, minor signs of axonal degeneration distal to the affected brachial plexus have been described. Several minor dysmorphic features are associated with HNA, including short stature, hypotelorism, epicanthal folds, and cleft palate, but clear segregation of the dysmorphism with the neuropathy has not been proved. In the hereditary form, as in the sporadic form, individual episodes of symptoms may be preceded by infections or immunization (Jacob et al., 1961; Taylor, 1960; Tsairis et al., 1972).

Orstavik et al. (1997) described a mother and son with recurrent episodes of brachial plexus neuropathy. They suggested that the hereditary form of this disorder is usually associated with dysmorphic features (Airaksinen et al., 1985), such as hypotelorism, small palpebral fissures, and a small mouth. Although their patients had only very slight dysmorphic features, they concluded that they represented the inherited form.

Pellegrino et al. (1997) noted that dysmorphic features, including hypotelorism, long nasal bridge, and facial asymmetry, are frequently associated with this disorder.

Meuleman et al. (2001) reviewed the topic of hereditary neuralgic amyotrophy. They pointed out that 2 different clinical courses had been discerned: the classic relapsing-remitting course and a chronic undulating course, consistent with the evidence of genetic heterogeneity.

Jeannet et al. (2001) cited 27 patients with hereditary neuralgic amyotrophy from 7 families. Twenty-five patients had an average of 3 attacks of brachial neuritis. The right arm was involved more frequently. Cleft palate was present in 4 individuals. Facial measurements showed significant hypotelorism in patients versus controls. Unusual skin folds and creases were observed on the necks of several individuals, as well as on the scalp of 1 man (cutis verticis gyrata). In 3 families, deep skin creases were present on the limbs of infants and toddlers who were subsequently affected by hereditary neuralgic amyotrophy. Thus, the phenotypic spectrum is wider than previously appreciated and involves nonneural tissues.

Kuhlenbaumer et al. (2005) summarized the clinical features of hereditary neuralgic amyotrophy, also called neuralgic amyotrophy with predilection for brachial plexus. The disorder, an autosomal dominant recurrent neuropathy affecting the brachial plexus, is triggered by environmental factors such as infection or parturition. The clinical hallmarks are recurrent painful brachial plexus neuropathies with weakness and atrophy of arm muscles and sensory loss. Full or partial recovery occurs in most affected individuals within weeks to months. A more common sporadic form of painful brachial plexus neuropathy, called Parsonage-Turner syndrome, is clinically indistinguishable from HNA. Attacks of brachial plexus neuritis are often triggered by infections, immunizations, and strenuous use of the affected limb. Inflammatory changes in the blood and brachial plexus have been shown, suggesting involvement of the immune system. Dysmorphic features such as hypotelorism, epicanthal folds, and, rarely, cleft palate had been found in many but not all individuals with the disorder (Pellegrino et al., 1997).

Laccone et al. (2008) reported a brother and sister, aged 2.5 years and 6.5 years, respectively, with HNA and dysmorphic features. Dysmorphic features included hypotelorism, upslanting palpebral fissures, very thin, downslanting eyebrows, deep-set eyes, and blepharophimosis. Both sibs also had slight ptosis, epicanthal folds, depressed nasal root, microstomia, and low-set dorsally rotated ears with very broad upper helices. The boy had cleft palate. Developmental milestones for both were normal. On history, the father and paternal grandmother reported painful episodes of brachial muscle weakness with residual wasting and paralysis, consistent with HNA. Photographs of the father and grandmother as children showed similar dysmorphic features as in the 2 sibs. Genetic analysis identified a heterozygous mutation in the SEPT9 gene (R88W; 604061.0001) in all 4 individuals. The boy was originally thought to have BPES (110100), but that was excluded by genetic analysis. His sister had experienced a painful attack in her elbow at age 2.5 years and was incorrectly diagnosed with radial head subluxation at that time. Laccone et al. (2008) emphasized that wider recognition of the characteristic dysmorphic features of HNA can facilitate clinical diagnosis of this syndrome.

Diagnosis

Kuhlenbaumer et al. (2000) presented diagnostic guidelines for HNA, as reported on behalf of the European CMT Consortium. Pertinent exclusion criteria are absence of pain before or during attacks, signs of a generalized neuropathy, and presence of mutations in the PMP22 gene.

Mapping

Distinction from HNPP

Although hereditary neuralgic amyotrophy with predilection for the brachial plexus has some similarities to hereditary neuropathy with liability to pressure palsies (HNPP; 162500), several studies have confirmed that they are distinct disorders. HNPP is associated with deletion or abnormal structure of the PMP22 gene (601097) on 17p12-p11.2, the same gene that is duplicated or the site of point mutations in Charcot-Marie-Tooth disease type Ia (CMT1A; 118220). In affected members from 3 pedigrees with neuralgic amyotrophy, Chance et al. (1994) did not find the deletion associated with HNPP or any abnormality in the PMP22 structure. Gouider et al. (1994) showed that in affected members of 2 families with neuralgic amyotrophy, the PMP22 gene is not deleted, duplicated, or mutated and that the disease is not linked to any other gene in the HNPP region. Thus, the genetic evidence supported the conclusion that from clinical, electrophysiologic, and pathologic studies, the 2 disorders are distinct. Windebank et al. (1995) reported the same findings from a larger study involving fluorescence in situ hybridization using a DNA probe that hybridizes to 17p11.2 in the area deleted in HNPP. Their study involved 14 persons from 4 unrelated families with HNPP and 7 members from 3 unrelated families with inherited brachial plexus neuropathy. While all of the HNPP patients showed deletion, Windebank et al. (1995) found that all 10 control subjects and the 7 patients with inherited brachial plexus neuropathy showed normal fluorescent signals on both chromosomes 17.

Linkage to Chromosome 17q

Pellegrino et al. (1996) analyzed 2 pedigrees to demonstrate linkage of HNA to markers from the distal part of 17q. In a large Turkish pedigree with 14 affected members, Stogbauer et al. (1997) confirmed the presence of the mutant locus on 17q, and by defining flanking markers, refined the localization of the locus to a 16-cM region on 17q24-q25. Stogbauer et al. (1997) commented that genes coding for connective tissue proteins may be critical for hereditary neuralgic neuropathy through both direct pressure and diminished blood supply. As triggers, strenuous use of the affected arm and parturition have been observed. Possible immunologic mechanisms as a trigger were suggested by Geiger et al. (1974).

Pellegrino et al. (1997) assessed genetic homogeneity in 6 pedigrees with HNA and found linkage of the NAPB locus to chromosome 17; combined lod score = 10.94, theta = 0.05 with marker D17S939. Analysis of crossovers placed the locus within an approximately 4.0-cM interval flanked by D17S1603 and D17S802. Analysis of DNA from a human/mouse somatic cell hybrid using these linked markers suggested that band 17q25 harbors the NAPB locus.

Meuleman et al. (2001) excluded several genes that map to the 17q25 region as candidates involved in the causation of HNA: MLL septin-like fusion gene (MSF; 604061), the thymidine kinase-1 gene (TK1; 188300), and the SEC14-like 1 gene (SEC14L1; 601504). These genes mapped on the clone contigs of the hereditary neuralgic amyotrophy region.

With a high-density set of DNA markers from 17q25, Watts et al. (2002) narrowed the locus for hereditary neuralgic amyotrophy to an interval of approximately 1 Mb flanked by markers D17S722 and D17S802. They compared genotypes of 12 markers from 7 pedigrees from the U.S. that showed linkage to 17q25. The haplotypes identified a founder effect in 6 of the 7 pedigrees with a minimal shared haplotype that further refined the locus to an interval of approximately 500 kb. The findings suggested that, for the pedigrees from the U.S., there are at least 2 different mutations in the responsible gene.

Heterogeneity

Klein et al. (2009) identified a common conserved 17q25 sequence in affected members of 5 North American kindreds with HNA, consistent with a founder effect. However, no mutations were identified in the SEPT9 gene in these families, and SEPT9 mRNA levels were similar to controls.

Molecular Genetics

Kuhlenbaumer et al. (2005) performed linkage analysis in 10 previously reported multigeneration families with the classical phenotype of what they referred to as hereditary neuralgic amyotrophy (HNA). The families were derived from different geographic areas. Segregation analysis of short tandem repeat (STR) markers in informative recombinants of these families allowed further reduction of the HNA locus to a 600-kb interval containing only 2 known genes, SEC14L1 and SEPT9 (604061). Kuhlenbaumer et al. (2005) sequenced the coding region of SEPT9 including its untranslated regions (UTRs), multiple splice variants, and alternative first exons. In 4 families with HNA, they found a sequence variation (262C-T) in exon 2 of the SEPT9 gene. This transition caused the amino acid change R88W (604061.0001). These 4 families did not share a common disease-associated haplotype, suggestive of a mutation hotspot rather than a founder mutation. The genomic variation occurred at a potential hypermutable CG dinucleotide. In one family they detected an S93F missense mutation (604061.0002). In another family a variation was found in the 5-prime UTR of the SEPT9 alpha transcript (604061.0003).

In 8 of 42 unrelated pedigrees with HNA, Hannibal et al. (2009) identified mutations in the SEPT9 gene. The R88W mutation was consistent with a founder effect.

Landsverk et al. (2009) identified an intragenic 38-kb tandem duplication in the SEPT9 gene (604061.0004) that was linked to HNA in 12 North American families that shared a common founder haplotype. The duplication was identical in all pedigrees and included the 645-bp exon in which 2 previous HNA mutations had been found.

Collie et al. (2010) identified heterozygous tandem duplications affecting the SEPT9 gene in affected individuals from 6 unrelated families with HNA. All of the duplications were of different sizes with unique breakpoints and ranged size from 30 to 330 kb. The smallest common region shared by all duplications encompassed the proline-rich 645-bp exon in which HNA-linked mutations had previously been identified, suggesting that this region is involved in the pathogenesis of the disorder. Five of the duplications generated larger protein products compared to the wildtype protein. The largest 330-kb duplication spanned the entire SEPT9 gene and included a portion of the adjacent gene SEC14L1 (601504); this duplication did not generate aberrant transcripts or proteins, suggesting that increased dosage of SEPT9 alone may be responsible for the disorder. There was no single mechanism responsible for the generation of these duplications. The HNA phenotype was the same as that observed for other mutations in the SEPT9 gene.

History

Meuleman et al. (2001) suggested that Dreschfeld (1886) may have published the first report of hereditary neuralgic amyotrophy, that of a 43-year-old woman who had suffered 3 episodes of painful upper limb weakness and whose sister had suffered 7 similar attacks.