1- Department of Medical Genetics, 3- Department of Pathology, Nizam's Institute of Medical Sciences,2- Diagnostics Division, Centre for DNA Fingerprinting ...
Molecular autopsy identifies recombinant GBA gene in a case of Gaucher disease with Ichthyosis phenotype Shagun
1,2 Aggarwal ,
S. Jamal Mohamed Nurul
2 Jain ,
Ashwani
3 Tandon ,
Aneek D.
2 Bhowmik ,
Ashwin
2 Dalal
1- Department of Medical Genetics, 3- Department of Pathology, Nizam’s Institute of Medical Sciences,2- Diagnostics Division, Centre for DNA Fingerprinting and Diagnostics, Hyderabad
Introduction Molecular workup forms an important part of the perinatal autopsy and helps in confirming the diagnosis of a suspected genetic disease in a fetus with suggestive gross and microscopic findings. This case report illustrates the identification of perinatal lethal Gaucher disease in a fetus with ichthyosis, a dermatosis known to be genetically heterogeneous.
Case report Third degree consanguineous couple. History of previous pregnancy termination due to antenatal detection of cardiomegaly and polyhydramnios Present pregnancy: USG at 16 weeks- Echogenic bowel, USG at 27 weeks- Bilateral clenched hands, Micrognathia, cardiomegaly, growth restriction Generalised skin thickening. Taut, thick, glistening skin on hands, feet and face Short digits with nodular joints and telephalyngy, labial thickening
Autopsy findings
Thick ear lobules, thick lips with eclabium, thick, upturned nares with flat, short nose, ectropion, severe micrognathia
Structure of GBA genes and recombinants 16 Kb GBA GBAP
Intrathoracic examinationcardiomegaly with thick looking ventricular walls Intra-abdominal examinationHepatosplenomegaly
Molecular study
55bp deletion in D409H in normal control normal control L444P,A456P,V460V in normal control
References
Mother’s sample No 55bp deln, D409H Heterozygous L444P, A456P,V460V present
Conclusion
Simple PCR leads to coamplification of GBA and pseudogene
A456P
7765 bp long PCR product
V460V
Reciprocal and Nonreciprocal Recombination at the Glucocerebrosidase Gene Region: Implications for Complexity in Gaucher Disease. Am. J. Hum. Genet. 72:519–534, 2003. Type 2 Gaucher disease: the collodion baby phenotype revisited. Arch Dis Child Fetal Neonatal Ed 2000;82:F163–F166. Novel Mutations in the Glucocerebrosidase Gene of Brazilian Patients with Gaucher Disease. JIMD Reports DOI 10.1007/8904_2012_174.
Molecular testing forms an important part of fetal autopsy, Confirms clinical diagnosis Identifies underlying mutation, Can elucidate interesting genetic mechanisms, Improves genotype-phenotype correlation
L444P
A456P
V460V
Father’s sample No 55bp deln, D409H Heterozygous L444P, A456P,V460V present
L444P
Abdominal wall
Back
No blood or fibroblasts from fetus available Beta glucosidase enzyme assay on parental leucocytes Mother: 4.4 ,Father : 5.1,Normal : 6– 9 (nmol/hr/mg) Control sample No 55bp deln,D409H No L444P,A456P,V460V
V460V (G/C)
Dorsum of hand
Arm
Biochemical study
Long PCR leads to selective amplification of GBA gene
55bp Rec 1 (NciL)- L44P,A456P,V460V deletion D409H L444P A456P (G/C) (T/C) (G/C) Rec 2 (TL)- D409H,L444P,A456P,V460V Highly Homologous regions prone for Rec 3- 55bp deln, D409H,L444P,A456P,V460V recombination events
L444P
Primers for Long PCR
Histopathology- Skin findings suspicious of Ichthyosis Autolytic changes in liver,spleen and cardiac tissue
A456P
V460V
Discussion Both parents found to be heterozygous for the Rec Ncil recombinant allele Fetus retrospectively confirmed to be perinatal lethal Gaucher disease Rec Ncil allele: most common recombinant of GBA gene Presumed to occur from gene fusion/crossover event between GBA and GBAP at intron 9 or intron 9/exon 10 junction Homozygous state of RecNcil allele-Two cases of Afghani and Lebanese origin with perinatal lethal Gaucher disease Compound heterozygous state leads to complete phenotypic spectrum of Gaucher disease