Departments of *Paediatrics, Gastroenterology and Nutrition and †Pathophysiology, Medical University, Wroclaw, Poland; ‡Children's Hospital, Technical University Dresden, Germany
The molecular studies were supported by a grant from the Deutsche Forschungsgemeinschaft to AH.
Address correspondence and reprint requests to Dr. Franciszek Iwanczak, Paediatrics, Gastroenterology and Nutrition Department, Curie-Sklodowskiej 50/52, 50-368 Wroclaw, Poland (e-mail: firstname.lastname@example.org).
The triple A syndrome (MIM*231550), known as Allgrove syndrome, is a rare disease characterized by the triad of achalasia, adrenal insufficiency and deficient tear production (alacrima). In most patients, neurologic and dermatological abnormalities (e.g., palmoplantar hyperkeratosis) are associated features. Other symptoms, including short stature, facial dysmorphic features, osteoporosis and microcephaly, indicate that triple A syndrome is in fact a multisystemic disorder (1-3). Progressive neurologic symptoms of triple A syndrome include autonomic and peripheral motor and sensory neuropathy, mental retardation, dementia, dysarthria, cerebellar ataxia and hyperreflexia (4-6). Thus some authors propose that autonomic and other neurologic abnormalities should be considered as an integral feature of triple A syndrome and have suggested the term "4A syndrome" (7-11).
The pathogenesis and pathophysiology of this syndrome are obscure. It is supposed that the disease is a result of progressive failure of the autonomic nervous system, particularly of the cholinergic system (12). Recently, Khelif et al. revealed the lack of neuronal NO synthase and fibrosis of the intermuscular plane in the defective cardia of patients with triple A syndrome (13).
Using genetic linkage analysis in a large number of families, a locus involved in triple A syndrome was identified on chromosome 12q13 (14,15). The gene affected in patients with triple A syndrome was identified in this locus and called AAAS (16,17). The AAAS gene is mutated in a homozygous or compound heterozygous state in nearly all kindreds with triple A syndrome studied to date (16-19). In the AAAS gene, various mutations have been found, including missense, nonsense, frameshift and splice mutations.
The AAAS gene encodes a 546 amino acid protein and is predominantly expressed in endocrine and neuroendocrine tissues as well as in cerebral structures (16,17). Mutations in the AAAS gene can lead to a changed or truncated protein. The AAAS protein, called ALADIN (alacrima-achalasia-adrenal insufficiency neurologic disorder), belongs to the large family of WD-repeat proteins and is a member of the nuclear pore protein complex (NPC) (20). Disease-associated AAAS mutations result in a failure of ALADIN to localize to NPCs, in that the mutant proteins were found predominantly in the cytoplasm (16,21,22).
A 7-year-old boy is the second of three children of healthy parents. Family history revealed that parents were third degree relatives. The patient was born at term after normal pregnancy and delivery (birth weight, 3200 g; length, 54 cm; Apgar score 10). The milestones of development during infancy were normal. The parents observed a lack of tears in their son from early infancy, but never discussed this problem with an ophthalmologist, because the child had no complaints. At 5 years of age, after a 6-month history of weakness, fatigability, sporadic vomiting, excessive sleepiness and hyperpigmentation, primary adrenocortical insufficiency was diagnosed. The boy was treated with fludrocortisone with good results, but vomiting without nausea persisted. During the months following diagnosis of adrenocortical insufficiency, vomiting during and directly after meals intensified. Additionally, dysphagia of solid food and retrosternal pain appeared.
At the age of 7 years, the patient was admitted to the Pediatric Gastroenterology and Nutrition Department with suspicion of gastroesophageal reflux disease (GERD). Physical examination revealed that the body weight and length were within the normal range, both 50th percentile; the skin was hyperpigmented, dry and coarse with palmar hyperkeratosis and excoriations. Laboratory findings were within normal range, with the exception of high concentration of immunoglobulin IgE (238 IU/ml, normal range: 3-36,4 IU/ml).
Barium swallow radiography showed dilatation of the esophagus and stasis of food typical of achalasia. During examination in supine position, the absence of normal peristalsis in the mid and distal esophagus was observed. Esophageal manometry showed an elevated pressure of the lower esophageal sphincter (LES), with failure of LES relaxation and absence of esophageal peristalsis. Gastric emptying scintigraphy, using technetium 99 m colloid, revealed retention of isotope in the esophagus for more than 60 minutes. The results of these examinations confirmed the diagnosis of achalasia.
Schirmer test confirmed the absence of tears. No corneal injuries were found in the ophthalmological examination.
In the presence of these findings, primary adrenocortical insufficiency, achalasia and alacrima, as well as skin abnormalities (palmar hyperkeratosis), triple A syndrome was suspected. The diagnosis of triple A syndrome was confirmed by genetic analysis. We identified a homozygous T<C transition in exon 8 of the AAAS gene. This mutation results in a change of serine at amino acid position 263 into proline (S263P) (Fig. 1).
The achalasia required surgical treatment. The patient underwent a Heller cardiomyotomy with funduplication with very good results. Vomiting and dysphagia improved considerably. The boy receives replacement therapy for adrenocortical insufficiency under the supervision of an endocrinologist. At present our patient doesnt require any artificial tears.
Triple A syndrome was firstly described by Allgrove in 1978 as a disease with autosomal recessive inheritance (1). Subsequently, single reports noted the same association between glucocorticoid deficiency, achalasia and deficient tear production (23,24). Patients with triple A syndrome suffer from the three cardinal features of adrenal failure, achalasia and alacrima. Usually the disorder manifests in the first decade of life with alacrima being the earliest and most consistent symptom, followed by glucocorticoid deficiency and achalasia, as observed in our patient (1-3). The presenting symptom of our patient was alacrima. The deficiency in tear production was observed from early infancy, but the child was not diagnosed by ophthalmologist because of the absence of clinical problems. In fifth year of life adrenalcortical insufficiency (Addison disease) was diagnosed. In the seventh year of life, achalasia was diagnosed based on the clinical picture, barium contrast radiography, scintigraphy and esophageal manometry.
Triple A syndrome can be associated with microcephaly, mental retardation, optic atrophy, ataxia and other autonomic neurologic abnormalities (7-11). A large series of triple A syndrome patients were reported by Grant et al. It was found that they developed neurologic abnormalities including peripheral sensory, motor and autonomic neuropathy, hyperreflexia, muscle weakness, dysarthria and mental retardation (7). Gazarian et al. and others also have reported autonomic and peripheral neuropathies in patients with this condition (8). To date, no neurologic abnormalities have been recognised in our patient, and a neurologic examination is being performed every 6 months.
To confirm the triple A syndrome we sequenced the entire coding region including exon-intron boundaries of the AAAS gene. We identified a homozygous missense mutation with T<C transition in exon 8 resulting in a change of serine at amino acid position 263 into proline (S263P). Handschug et al. presented nine families with triple A syndrome and found eight different mutations occurring in different exons (17). They identified three missense mutations (Q15K, H160R and S263P), three nonsense mutations (W84X, R286X and R342X) and two frameshift deletions of 1 and 2 base pairs (552-553delTT and 1471delC, respectively) (17). The S263P mutation seems to be one of the most frequent mutations in the AAAS gene occurring in not-related triple A families from European countries (17,18). Handschug et al. found the S263P mutation in four families (three of Polish and one of German origin) (17). They suggested that this phenomenon seems to be based on a founder effect. Huebner et al. and Prpic et al. found the same mutation in others families (18,25). The AAAS gene product belongs to the WD-repeat protein families. The function of wildtype and mutant AAAS protein is not clear to date. However, taking into consideration the frequency of the mutation S263P, the authors are convinced that it impairs AAAS function. Recently, it was found that ALADIN protein is a member of the nuclear pore protein complex (NPC) (20). Cronshaw et al. show that the AAAS protein with the S263P mutation is mislocalized in the cytoplasm and does not target correctly to the NPC and exhibit a severe, heterogeneous phenotype with occurrence of all three main symptoms of the triple A syndrome including the mental retardation and progressive peripheral neuropathy (21). Based on our and other results it should be considered that the S263P mutation is a typical for Slavonic origin of the families with triple "A" syndrome. However the studies by Huebner et al. and Prpic et al. that analyse the genotype and phenotype correlation revealed a highly variable occurrence, age of onset and severity of all clinical symptoms among patients with the same AAAS mutation. They suggested that other modifying genes or factors can determine the phenotype of triple A syndrome (2,25).
DNA isolated from two sisters of the index patient was also sequenced. Family history revealed that the parents of our patients were consanguineous. One sister is homozygous normal at this nucleic acid position and the second has the S263P mutation in a heterozygous state and is therefore a healthy carrier. To date, all heterozygous family members are healthy and do not show any symptoms of the disease.
Our case suggests that the final diagnosis of the triple A syndrome should be confirmed by molecular analysis in patients with suspected disorder. Molecular investigation can be useful when typical features of 3A syndrome are presented. Molecular analysis should be also performed in the patients family. Patients with triple A syndrome show a considerable phenotype variability, including neurologic abnormalities. Therefore, these patients require careful neurologic investigation.
Acknowledgments: The technical assistance of Heike Petzold and Katrin Handschug is kindly acknowledged.
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