Unveiling genetics of non-syndromic albinism using whole exome sequencing: A comprehensive study of TYR, TYRP1, OCA2 and MC1R genes in 17 families.

BACKGROUND: Oculocutaneous albinism (OCA) is a group of skin depigmentation disorders. Clinical presentation of OCA includes defects in melanocyte differentiation, melanin biosynthesis, and melanosome maturation and transport. OBJECTIVES: A molecular diagnostics study of families presenting oculocutaneous albinism. METHODS: In this study, 17 consanguineous OCA families consisting of 93 patients were investigated. Whole Exome Sequencing (WES) of the index patient in each family were performed. Short listed variants of WES were Sanger validated for Mendelian segregation in obligate carriers and other available family members. Variant prioritization and pathogenicity were classified as per the criteria of American College Medical Genetics and Genomics (ACMG). Comparative computational modelling was performed to predict the potential damaging effect of the altered proteins. RESULTS: 15 pathogenic variations: c.132 T > A, c.346C > T, c.488C > G, c.1037G > A in TYR, c.1211C > T, c.1441G > A, c.1706_1707insT, c.2020C > G, c.2402G > C, c.2430del, in OCA2, c.1067G > A in TYRP1 and c.451C > T, c.515G > T, c.766C > T, c.917G > A in MC1R genes were identified. Three variants in OCA2 gene were characterized: c.1706_1707insT, c.2430del, and c.2402G > C, all of which were not reported before in OCA families. CONCLUSION: A few studies focusing on mutation screening of OCA patients have been reported before; however, this study has uniquely presents the Pakhtun ethnic population residing on the North-Western boarder. It explains that TYR, OCA2, TYRP1, and MC1R variations lead to non-syndromic OCA phenotype The overlapping phenotypes of OCA can precisely be diagnosed for its molecular pathogenicity using WES. This study recommends WES as a first-line molecular diagnostic tool, and provides a basis for developing customized genetic tests i.e. pre-marital screening to reduce the disease burden in the future generations.

Superficial Circumflex Iliac Artery Free Flap for Coverage of Hand Injuries.

Open de-gloving hand injuries with exposed tendons and bones require coverage by a flap. Conventionally used groin or abdominal flaps are cumbersome to patients due to extensive dressing and prolonged passive positioning of the hand until pedicle division. Superficial circumflex iliac artery (SCIA) flap is evolved from a traditional groin flap, and because of its thinness, pliability, and concealed donor site, it is an ideal option for single-stage reconstruction of traumatic hand defects avoiding discomforting passive hand position, joint stiffness, and unexpected flap avulsion which were associated with traditional groin flap. All patients with exposed bones or tendons due to traumatic hand injuries who opted for free flap coverage during the year 2018 to 2020 were enrolled in our study. After initial debridement, the wound was covered with a free SCIA flap. Duration of hospital stay, days out of work, the number of dressings required, postoperative complications, and any secondary procedures for flap readjustment were noted till six months postoperatively. A total of eight patients were included in the study. The mechanism of injury was road traffic accidents in a single patient and occupational injury in eight patients. The average duration of hospital stay was six days after reconstructive surgery. The average number of dressings a patient had was 18, and only two patients required flap thinning. Only one patient had a postoperative infection which was managed with dressings and antibiotics. One patient had peripheral flap necrosis. We had zero flap re-exploration. Therefore, we conclude that hand defects coverage with SCIA flap leads to a smaller number of working days lost and rarely requires secondary procedures.

ALTERING THE MARKING OF THE REVERSE POSTERIOR INTEROSSEOUS ARTERY FLAP.

Background: Full-thickness defects on the dorsum of the hand requires thin, soft, and pliable skin for which there are limited locoregional flaps. The reverse posterior interosseous artery (PIA) flap based on the communicating artery fulfills all above requirements and can reach upto the fingers. However, there has been discrepancy in the surface marking of the flap and the anatomical position of the vessel pedicle. We share our alteration with the marking and ease of harvesting this flap. Method and material: This is a prospective study conducted at a private teaching hospital in Karachi, over a period of 2 years from November 2017 to December 2019. After taking consent and ensuring confidentiality of all patients who had PIA flap reconstruction, we collected patient's demographic details, mode of injury, and flap surface area. We altered the described skin marking and took measures to prevent venous congestion and noted the outcomes in term of flap congestion and flap loss. Results: Twenty-eight patients with a mode age of 32 years were operated during this period. The majority (64.2%) had a motor vehicle accident and machine injuries. The mean surface area of flaps was 6 × 10 cm2, and 11 (39.2%) flaps had venous supercharging. All patients had a 10-20° wrist extension splint for 2 weeks. The mean follow-up of the patients was 14 ± 5 days, and 6 (21.4%) flaps developed a minimal marginal flap loss, which was managed conservatively. Conclusion: By minimally altering our surface marking, we experienced a easy and quick harvesting of this flap. However, one has to be vigilant and take all described precautions for venous congestion.

Two missense mutations in GPNMB cause autosomal recessive amyloidosis cutis dyschromica in the consanguineous pakistani families.

BACKGROUND: Amyloidosis cutis dyschromica (ACD) is a rare variant of cutaneous amyloidosis. This disorder often clusters in families, and it has been suggested that genetic factors might be involved in its development. OBJECTIVE: To identify the genetic causes of ACD, we recruited a consanguineous Pakistani family with multiple cases of ACD that display a recessive mode of inheritance. METHODS: We performed whole-exome sequencing of samples from 7 members of this family, followed by bioinformatic and in silico analyses to identify the causative variant. For the replication study, we recruited a British family with Pakistani ancestry, and sequenced all exons of glycoprotein non-metastatic melanoma protein b (GPNMB) to identify mutations. We also investigated effects of the mutations on the stability of the GPNMB protein using the I-TASSER three-dimensional modeling tool. RESULTS: We found a novel homozygous mutation, p.Gly363Val (c.1088 G>T), in GPNMB in all affected cases. In a replication study, another homozygous missense mutation in GPNMB, pIle174Met (c.522 C>G), was carried by the affected son. The two mutations were not observed in our in-house data set comprising 217 healthy Pakistani individuals or in The Genome Aggregation Database. Our structural modeling of GPNMB suggested that p.Gly363Val enhanced its stability, whereas p.Ile174Met caused instability. CONCLUSIONS: This study reports two novel missense mutations in two Pakistani families that cause ACD. The mutations appear to influence GPNMB stability, as revealed by protein modeling.

Deletion mutation in BSCL2 gene underlies congenital generalized lipodystrophy in a Pakistani family.

BACKGROUND: Congenital generalized lipodystrophy (CGL) also known as Berardinelli-Seip Congenital Lipodystrophy (BSCL) is a genetically heterogeneous disorder characterized by loss of adipose tissues, Acanthosis nigricans, diabetes mellitus, muscular hypertrophy, hepatomegaly and hypertriglyceridemia. There are four subclinical phenotypes of CGL (CGL1-4) and mutations in four genes AGPAT2, BSCL2, CAV1 and PTRF have been assigned to each type. METHODS: The study included clinical and molecular investigations of CGL disease in a consanguineous Pakistani family. For mutation screening all the coding exons including splice junctions of AGPAT2, BSCL2, CAV1 and PTRF genes were PCR amplified and sequenced directly using an automated DNA sequencer ABI3730. RESULTS: Sequence analysis revealed a single base pair deletion mutation (c.636delC; p.Tyr213ThrfsX20) in exon 5 of BSCL2 gene causing a frame shift and premature termination codon. CONCLUSION: Mutation identified here in BSCL2 gene causing congenital generalized lipodystrophy is the first report in Pakistani population. The patients exhibited characteristic features of generalized lipodystrophy, Acanthosis nigricans, diabetes mellitus and hypertrophic cardiomyopathy. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1913913076864247.