Sickle cell retinopathy and other chronic complications of sickle cell anemia: A clinical study of 84 Sub-Saharan African cases (Cameroon).

OBJECTIVE: Sickle retinopathy is a severe complication of sickle cell disease than can lead to blindness. We aim to describe the epidemiology of sickle retinopathy in homozygous sickle cell (SS) African patients and to analyze its association with non-ophthalmologic disease complications of sickle cell anemia. METHODS: We conducted a nested study within the CADRE cohort in Cameroon. Eighty-four consecutive SS outpatients, aged 10 years and older, with no visual symptoms, underwent an ophthalmologic examination. Mean age was 23±10 years. Clinical and biological features were compared between patients with and without sickle retinopathy. We compared the prevalence of the clinical complications and main biological characteristics in patients with and without sickle retinopathy using a univariate logistic regression. The same analysis was used to compare the patients with non-proliferative sickle retinopathy to those with proliferative sickle retinopathy. Statistical analyses were done using the R software (version 3.1.2). RESULTS: Fifty-two patients (62%) displayed sickle retinopathy, among them 23 (27%) had a non-proliferative sickle retinopathy, and 29 (35%) had proliferative sickle retinopathy. Patients with proliferative sickle cell retinopathy had a mean age of 28±11 years. Sickle retinopathy was associated with higher hemoglobin level (P=0.047) and fewer leg ulcers (P=0.018). Proliferative SR was associated with increasing age (P=0.008) and male sex (P=0.025) independently of the hemoglobin level. CONCLUSIONS: Sickle retinopathy is particularly frequent in sub-Saharan sickle cell SS patients, which advocates for early systematic screening.

Epidemiology of venous thromboembolism in Africa: a systematic review.

Essentials Venous thromboembolism (VTE) is among the three main causes of cardiovascular disease worldwide. This review is the first to summarize the epidemiology of VTE in African populations. The prevalence of VTE in Africa is high following surgery, in pregnancy and post-partum. At least one quarter of patients at risk of VTE in Africa are not receiving prophylaxis. SUMMARY: Background Venous thromboembolism (VTE) is among the three leading causes of cardiovascular disease worldwide. Despite its high burden, there has been no previous study summarizing the epidemiology of VTE in African populations. Hence, we conducted this systematic review to determine the prevalence, incidence and mortality associated with VTE, and to evaluate the use of VTE prophylaxis in Africa. Methods We searched PubMed, Scopus and African Journals Online to identify articles published on VTE in Africa from inception to November 19, 2016, without language restriction. The reference list of eligible articles were further scrutinized to identify potential additional studies. Results Overall, we included 21 studies. The great majority of the studies yielded a moderate risk of bias. The prevalence of deep vein thrombosis (DVT) varied between 2.4% and 9.6% in postoperative patients, and between 380 and 448 per 100 000 births per year in pregnant and postpartum women. The prevalence of pulmonary embolism (PE) in medical patients varied between 0.14% and 61.5%, with a mortality rate of PE between 40% and 69.5%. The case-fatality rate after surgery was 60%. Overall, 31.7-75% of the patients were at risk of VTE, and between 34.2% and 96.5% of these received VTE prophylaxis. Conclusion The prevalence of VTE and associated mortality are high following surgery, and in pregnant and postpartum women in Africa. At least one-quarter of patients who are at risk for VTE in Africa are not receiving prophylaxis. These results are generated from studies with small sample size, highlighting an urgent need for well-designed studies with larger sample size to evaluate the true burden of VTE in Africa.

Ketosis-prone atypical diabetes in Cameroonian people with hyperglycaemic crisis: frequency, clinical and metabolic phenotypes.

AIM: It is unclear whether ketosis-prone diabetes is a specific type or a subtype of Type 2 diabetes. We aimed to describe the clinical and metabolic features of ketosis-prone diabetes in a sub-Saharan population. METHODS: We consecutively enrolled and characterized 173 people with non-autoimmune diabetes admitted for hyperglycaemic crisis at the Yaoundé Central Hospital, Cameroon. Blood samples were collected for fasting glucose, HbA1c , lipid profile and C-peptide assays with insulin resistance and secretion estimation by homeostasis model assessment. People were classified as having Type 2 diabetes (n = 124) or ketosis-prone diabetes (n = 49). Ketosis-prone diabetes was sub-classified as new-onset ketotic phase (n = 34) or non-ketotic phase (n = 15). RESULTS: Ketosis-prone diabetes was found in 28.3% of the hyperglycaemic crises. Age at diabetes diagnosis was comparable in Type 2 and ketosis-prone diabetes [48 ± 14 vs 47 ± 11 years; P = 0.13] with a similar sex distribution. Overall BMI was 27.7 ± 13.4 kg/m2 and was ≥ 25 kg/m2 in 55.8% of those taking part, however, 73.5% of those with ketosis-prone diabetes reported weight loss of > 5% at diagnosis. Blood pressure and lipid profile were comparable in both types. Ketosis-prone diabetes in the ketotic phase was characterized by lower insulin secretion and higher serum triglycerides compared with non-ketotic ketosis prone and Type 2 diabetes. Type 2 and ketosis prone diabetes in the non-ketotic phase were comparable in terms of lipid profile, blood pressure, waist-to-hip ratio, BMI and fat mass, insulin secretion and insulin resistance indices. CONCLUSIONS: Ketosis-prone diabetes is likely to be a subtype of Type 2 diabetes with the potential to develop acute insulinopenic episodes.

Targeted genomic enrichment and massively parallel sequencing identifies novel nonsyndromic hearing impairment pathogenic variants in Cameroonian families.

In sub-Saharan Africa GJB2-related nonsyndromic hearing impairment (NSHI) is rare. Ten Cameroonian families was studied using a platform (OtoSCOPE®) with 116 genes. In seven of 10 families (70%), 12 pathogenic variants were identified in six genes. Five of the 12 (41.6%) variants are novel. These results confirm the efficiency of comprehensive genetic testing in defining the causes of NSHI in sub-Saharan Africa.

No evidence for clinical utility in investigating the connexin genes GJB2, GJB6 and GJA1 in non-syndromic hearing loss in black Africans.

BACKGROUND: Deafness is the most common sensory disability in the world. Globally, mutations in GJB2 (connexin 26) have been shown to play a major role in non-syndromic deafness. Two other connexin genes, GJB6 (connexin 30) and GJA1 (connexin 43), have been implicated in hearing loss, but these genes have seldom been investigated in black Africans. We aimed to validate the utility of testing for GJB2, GJB6 and GJA1 in an African context. METHODS: Two hundred and five patients with non-syndromic deafness from Cameroon and South Africa had the full coding regions of GJB2 sequenced. Subsequently, a carefully selected subset of 100 patients was further sequenced for GJB6 and GJA1 using Sanger cycle sequencing. In addition, the large-scale GJB6-D3S1830 deletion was investigated. RESULTS: No pathogenic mutations that could explain the hearing loss were detected in GJB2, GJB6 or GJA1, and the GJB6-D3S1830 deletion was not detected. There were no statistically significant differences in genomic variations in these genes between patients and controls. A comprehensive literature review supported these findings. CONCLUSION: Mutations in GJB2, GJB6 and GJA1 are not a major cause of non-syndromic deafness in black Africans and should not be investigated routinely in clinical practice.

Phenotypic and allelic distribution of the ABO and Rhesus (D) blood groups in the Cameroonian population.

Data on blood group phenotypes are important for blood transfusion programs, for disease association and population genetics studies. This study aimed at reporting the phenotypic and allelic distribution of ABO and Rhesus (Rh) groups in various ethnolinguistic groups in the Cameroonians. We obtained ABO and Rhesus blood groups and self-identified ethnicity from 14,546 Cameroonian students. Ethnicity was classified in seven major ethnolinguistic groups: Afro-Asiatic, Nilo-Saharan, Niger-Kordofanian/West Atlantic, Niger-Kordofanian/Adamawa-Ubangui, Niger-Kordofanian/Benue-Congo/Bantu/Grassfield, Niger-Kordofanian/Benue-Congo/Bantu/Mbam and Niger-Kordofanian/Benue-Congo/Bantu/Equatorial. ABO allelic frequencies were determined using the Bernstein method. Differences in phenotypic distribution of blood groups were assessed using the chi-square test; a P value <0.05 being considered as statistically significant. The frequencies of the antigens of blood groups O, A, B and AB were 48.62%, 25.07%, 21.86% and 4.45%, respectively. Rhesus-positive was 96.32%. The allelic frequencies of O, A and B genes were 0.6978, 0.1605 and 0.1416, respectively. Phenotypic frequencies of the blood groups in the general study population and in the different ethnolinguistic groups were in agreement with Hardy-Weinberg equilibrium expectations (P > 0.05). The frequencies of O, A, and B blood phenotypes were significantly lower, respectively, in the Nilo-Saharan group (P = 0.009), the Niger-Kordofanian/Benue-Congo/Bantu groups (P = 0.021) and the Niger-Kordofanian/West-Atlantic group. AB blood group was most frequent in the Niger-Kordofanian/Adamawa-Ubangui group (P = 0.024). Our study provides the first data on ethnic distribution of ABO and Rhesus blood groups in the Cameroonian population and suggests that its general profile is similar to those of several sub-Saharan African populations. We found some significant differences in phenotypic distribution amongst major ethnolinguistic groups. These data may be important for blood donor recruitment policy and blood transfusion service in Cameroon.