2.1 Clinical summary
The patient was a full term infant born to non-consanguineous parents. He presented at six weeks with fever, emesis, abdominal distention, and failure to thrive. Imaging studies showed hepatosplenomegaly and calcified adrenals. Enzymatic assay demonstrated undetectable LIPA activity.
Over the course of four weeks he developed acute liver failure with disseminated intravascular coagulation and cortical adrenal insufficiency. Due to the poor prognosis and limited treatment options, the parents elected palliative care. His liver function continued to worsen and in the days preceding death, the patient became less responsive and developed anuria and respiratory insufficiency secondary to multi-organ failure.
2.2 Molecular summary
DNA sequence analysis of all coding exons demonstrated a paternally inherited c.482delA mutation in exon 5 that results in a frameshift mutation at amino acid 161 (). This mutation leads to premature truncation of the protein at amino acid 179. We screened 200 chromosomes from ethnically matched controls by sequencing and did not detect any carriers of the c.482delA deletion.
Figure 1 A. Electropherogram of proband (top), father (middle) and mother (bottom) demonstrates a paternally inherited c.482delA mutation (arrow) in exon 5 that results in a frameshift mutation at amino acid 161. B. Quantitative PCR results for a probe within (more ...)
Initially, sequencing did not identify a second mutation so known SNPs were genotyped in LIPA to serve as markers to screen for lack of biparental inheritance to support a possible deletion mutation. Using this strategy, at rs2071509 the father was C/C, the mother appeared to be G/G, and the proband appeared to be C/C. Because the proband appeared to be homozygous for a paternal allele not carried by the mother, this data suggested that the mother had a deletion leading to hemizygosity in the proband and mother.
By genotyping additional SNPs, the deletion was found to include intron 3 but not to extend into exon 3. This finding was confirmed by real-time quantitative PCR using probes in exons 3, 4, and 10 which showed that the proband and mother have one copy of exon 4 compared to male and female controls (). Probes located in exons 3 and 10 demonstrated two copies in the proband and mother. This deletion, in conjunction with the c.482delA mutation, is the likely genetic cause of WD in this infant ().