A Novel ABCA4 Mutation Associated with a Late-Onset Stargardt Disease Phenotype: A Hypomorphic Allele?

BACKGROUND

Stargardt disease (STGD) is the most common juvenile hereditary macular dystrophy. In the majority of cases, the diagnosis is made prior to 20 years of age and usually leads to loss of central vision. Late-onset STGD affects a smaller number of patients. Identifying genetic changes which could be associated with clinically important differences in severity or presentation of the disease is important for understanding the mechanisms of visual loss and for planning future therapeutic approaches.

METHODS

We report a patient with the classic phenotype of STGD with late-onset mild disease exhibiting a slow clinical progression over 14 months of follow-up.

RESULTS

A 37-year-old man presented with STGD and good vision of 6/24 in the right eye and of 6/6 in the left eye as well as typical electrophysiology findings. Objective and subjective visual deterioration was not noted over a period of 14 months. Macular genetic testing revealed a novel missense mutation in ABCA4 (Thr829Met) combined with Gly1961Glu, a classic STGD mutation usually associated with a moderately severe phenotype.

CONCLUSIONS

It is suggested that the Thr829Met mutation could give rise to a hypomorphic allele of the ABC transporter with a resultant phenotype of comparatively mild STGD.

Abstract P2-01-22: The long term outcomes of Metasin RTqPCR intra-operative sentinel node analysis in early breast cancer

Background:

Axillary lymph node involvement is a prognostic factor in breast cancer and it is used to guide adjuvant therapy. Axillary clearance remains the standard of care in lymph node positive disease in most parts of the world. Usually this is performed as second procedure but immediate intra-operative node analysis allows clearance to be performed as part of the initial procedure where necessary.

The Metasin assay targets the breast epithelial cell markers CK19 and mammaglobin mRNA and detects the presence of breast tissue (metastatic disease) in the sentinel nodes. Evidence shows the Metasin assay to be fast (average assay time 41.2min) and accurate with a discordance rate below 4% compared with histology. The cost effectiveness of the assay has been reported in our previous studies.

Aim:

The aim of this study is to assess the risk of axillary recurrence following the use of the Metasin assay to guide axillary management.

Method:

This is a single centre retrospective study which included all patients presenting to a district general hospital with early clinically node negative breast cancer undergoing sentinel node biopsy between Oct 2011 and Dec 2014.

Alternate 2 mm slices of the node were examined intraoperatively using the Metasin assay and the remainder sent for histological examination. The results of the Metasin assay and histology were compared. The risk of axillary recurrence using the Metasin test to select patients for immediate axillary clearance was assessed.

Results:

1073 sentinel nodes from 545 patients were analysed during this three-year period. 2 patients were lost to follow up. 94 patients were node positive and underwent axillary clearance as part of their primary surgery. 449 patients had sentinel node biopsy with no further axillary procedure. There were 36 nodes (3.34%) with discordant results. Median follow up was 32 months (range 18 to 55 months).

Fourteen patients presented with recurrences (2.56%). The mean event free interval was 15 months. Of the 14 patients, 5 patients tested with Metasin had macrometastases and underwent immediate axillary clearance during the primary surgery. 7 patients were node negative and 2 patients were shown to have micrometastases. 11 patients recurred with distant metastases, 3 patients with local recurrence and 2 patients (0.36%) with axillary recurrences.

The two axillary recurrences occurred at 3 and 5 months after primary surgery. Both patients underwent Metasin intraoperative analyses of sentinel nodes which were negative. Subsequent histological examination confirmed no metastatic node involvement in one patient but micro-metastases in the other. Both of these patients had aggressive disease with local, axillary and distant metastasis and subsequently died of their disease.

Conclusions:

The Metasin assay is a reliable intraoperative test for sentinel node involvement and when used to guide surgical axillary management is associated with very low axillary recurrences (0.36% with a median follow up of 32 months).

Citation Format: Udayasankar S, Ashley E, Jenkins KS, Huws A, Sharaiha Y, Sai-Giridhar P, Thomas D, Munir A, Holt S, Khawaja S. The long term outcomes of Metasin RTqPCR intra-operative sentinel node analysis in early breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-01-22.

Mucopolysaccharidosis type VI in a Miniature Poodle-type dog caused by a deletion in the arylsulphatase B gene

AIM

To investigate and characterise an inborn error of metabolism in a dog with skeletal and ocular abnormalities.

METHODS

A 2.5-year-old small male Miniature Poodle-like dog was presented with gross joint laxity and bilateral corneal opacities. Clinical examination was augmented by routine haematology, serum chemistry, radiographs, pathology, enzymology and molecular genetic studies. Euthanasia was requested when the dog was 3 years of age because of progressively decreasing quality of life.

RESULTS

Radiology revealed generalised epiphyseal dysplasia, malformed vertebral bodies, luxation/subluxation of appendicular and lumbosacral joints with hypoplasia of the odontoid process and hyoid apparatus. These clinical and radiographic findings, together with a positive urinary Berry spot test for mucopolysaccharides, and metachromatic granules in leucocytes, were indicative of a mucopolysaccharidosis (MPS), a lysosomal storage disease. Histological lesions included vacuolation of stromal cells of the cornea, fibroblasts, chondrocytes, macrophages and renal cells. The brain was essentially normal except for moderate secondary Wallerian-type degeneration in motor and sensory tracts of the hind brain. Dermatan sulphate-uria was present and enzymology revealed negligible activity of N-acetylgalactosamine-4-sulphatase, also known as arylsulphatase B, in cultured fibroblasts and liver tissue. A novel homozygous 22 base pair (bp) deletion in exon 1 of this enzyme's gene was identified (c.103_124del), which caused aframe-shift and subsequent premature stop codon. The "Wisdom pure breed-mixed breed" test reported the dog as a cross between a Miniature and Toy Poodle.

CONCLUSIONS

The clinicopathological features are similar to those of MPS type VI as previously described in dogs, cats and other species, and this clinical diagnosis was confirmed by enzymology and molecular genetic studies. This is an autosomal recessively inherited lysosomal storage disease.

CLINICAL RELEVANCE

The prevalence of MPS VI in Miniature or Toy Poodles in New Zealand and elsewhere is currently unknown. Due to the congenital nature of the disorder, malformed pups may be subject to euthanasia without investigation and the potential genetic problem in the breed may not be fully recognised. The establishment of a molecular genetic test now permits screening for this mutation as a basis to an informed breeding policy.