Four siblings with achalasia, alacrimia and neurological abnormalities in a consanguineous family

The molecular basis of adrenocorticotrophin resistance syndrome

Adrenocorticotrophin resistance syndromes comprise familial glucocorticoid deficiency (FGD) and triple A syndrome, which are rare autosomal recessive diseases with distinct clinical features and molecular etiologies. Mutations of melanocortin-2 receptor (MC2R) have been described in segregation with FGD in 25% of patients. More recently melanocortin-2 receptor accessory protein (MRAP), a small single-transmembrane domain protein, was described as an essential protein for the traffic of MC2R and its expression on the plasma membrane. About 20% of FGD patients carry homozygous mutations of MRAP. The ALADIN protein (for alacrima/achalasia/adrenal insufficiency/neurologic disorder) was identified as the molecular basis of triple A syndrome. The elucidation of the genetic basis of the ACTH resistance syndrome has contributed to the better understanding of MC2R function. However, in some patients the molecular etiology is not yet known and awaits further genetic studies.

Allgrove syndrome with features of familial dysautonomia: a novel mutation in the AAAS gene

Allgrove syndrome (or triple-A syndrome) is a rare autosomal recessive disorder characterized by alacrima, achalasia, adrenal insufficiency (glucocorticoid in the majority of cases) and autonomic/neurological abnormalities. This disease is now known to be caused by mutation in the AAAS gene located on chromosome 12q13. Diagnosis should be readily available when the full-blown features are there, but it becomes less apparent when presentation is atypical or in the evolving process. We present a brother and sister (12 and 19 y old, respectively) born to consanguineous parents of Palestinian origin with Allgrove syndrome. The index patient was erroneously diagnosed to be a case of familial dysautonomia before the diagnosis of adrenal insufficiency was made at the age of 7.5 y, while his elder sister had only alacrima from birth and developed achalasia at the age of 15 y. She started to develop early evidence of adrenal disease at the age of 19 y. Both of them had neuroautonomic dysfunction. The diagnosis of Allgrove syndrome was confirmed in these two patients by studying the gene mutation in the family. The sequencing of the AAAS gene in the two patients identified a novel homozygous mutation within intron 5 (IVS5+1G-->A). Both parents as well as all three other children were heterozygous for the same mutation.

CONCLUSION

These two cases illustrate the heterogenous nature and the intrafamilial phenotypic variability of Allgrove syndrome.

A novel AAAS gene mutation (p.R194X) in a patient with triple A syndrome

OBJECTIVE

The clinical and molecular data of a patient with triple A syndrome are reported.

PATIENT

A 21-year-old male who was diagnosed for adrenal insufficiency at the age of 2 years after a severe attack of adrenal crisis. At the age of 4 years, achalasia and alacrima were diagnosed. Puberty started at the age of 17 years. At the same time, symptoms of central, peripheral, and autonomic nervous system dysfunction were noted. Later on, at the age of 20 years, a bone age delay of 6 years and severe osteoporosis was diagnosed.

RESULTS

A compound heterozygous AAAS mutation consisting of two mutations was found: a C > T transition in exon 7 resulting in a change of arginine at amino acid position 194 into a stop codon (Arg194X) at one allele, and a C > T transition in exon 12 resulting in a change of glutamine at amino acid position 387 into a stop codon (Gln387X) on the other allele.

CONCLUSION

The mutation in exon 7 (p.R194X) of the AAAS gene is a novel mutation which has not been found in any other family so far, whereas the second was already found in some other families. This case adds to the clinical and molecular spectrum of triple A syndrome and may provide a new insight into the functions of AAAS gene.

Triple A syndrome--clinical aspects and molecular genetics

The triple A syndrome or Allgrove syndrome (MIM*231550) is characterized by adrenocorticotropic hormone (ACTH) resistant Adrenal insufficiency, Achalasia of the cardia and Alacrima. In addition to the main features, patients frequently suffer from neurological disturbances. Dermatological abnormalities such as palmoplantar hyperkeratosis as well as other signs like short stature, microcephaly and osteoporosis point to the multisystemic character of the disorder. The molecular defect of the autosomal recessively inherited triple A syndrome is not known. We initially performed a systematic genome linkage scan in eight triple A families and were able to map the syndrome to a 6 cM interval on human chromosome 12q13 near the type II keratin gene cluster. A refinement of the triple A critical region was achieved by detailed haplotype analysis in a further 37 families from different ethnic backgrounds. There was no indication of genetic heterogeneity. The achalasia-alacrima (AA) syndrome which has been defined as a distinct clinical entity (MIM 200440) is most likely a variant of the triple A syndrome as shown by haplotype analysis in three AA families. We constructed a high-resolution BAC/PAC-based transcript map of the region which will greatly facilitate the identification of the triple A syndrome gene. The considerable intra- and interfamilial variability of the severity of the disorder implies a variable expression of an impaired pleiotropically acting gene.