A novel variant in ALMS1 in a patient with Alström syndrome and prenatal diagnosis for the fetus in the family: A case report and literature review

Abstract

Alström syndrome (AS) is a type of monogenic syndromic ciliopathy disease. The main clinical features of AS include cone‑rod malnutrition, sensorineural hearing loss, metabolic dysfunctions and multiple organ failure, which are caused by mutations of Alström syndrome protein 1 (ALMS1) gene. The current study aimed to identify pathogenic variants in a Chinese patient with AS and to review the relevant literature. Genomic DNA extracted from a 10‑year‑old male with AS was evaluated using a disease‑targeted gene panel. According to the bioinformatics analysis, the current study identified a novel frameshift mutation in exon 8 (c.2988_2989del, p.T996fs) and a rare nonsense mutation in exon 10 (c.9535C>T, p.R3179*) of the ALMS1 gene. Both parents were heterozygous carriers of this gene. To the best of our knowledge, these mutations have not been reported in normal population databases. According to the criteria of the American College of Medical Genetics and Genomics, the mutations were pathogenic. Based on these findings, amniotic fluid sample was used for prenatal diagnosis of the couple's fetus, and it was observed that the fetus carried c.9535C>T, and not c.2988del. During the follow‑up duration of >2 years of the fetus, it was confirmed that he was a healthy male. The results of the present study identified two compound heterozygous ALMS1 mutations in a patient with the symptoms of Alström syndrome and reported a novel ALMS1 variant which expands the spectrum of ALMS1 variants in AS.

Figure 1.

Clinical symptoms of the patient. The patient had narrow blepharoplasty, round face, sparse hair, wide and thick hand with short, thick fingers.

Figure 2.

Pedigree of the patient's family. Arrow indicates the patient.

Figure 3.

Confirmation of two mutations in the family members by Sanger sequencing. (A) c.2988_2989delAG (p.T996fs) mutation. (B) c.9535C>T (p.R3179*) mutation.

Figure 4.

Amino acid and mRNA sequences of Alström syndrome protein 1 and the predicted premature termination codons.