Congenital afibrogenaemia in a Kenyan child: case report.

Congenital afibrinogenaemia (CA), is a rare inherited bleeding disorder characterised by complete deficiency of fibrinogen in the plasma. Blood clotting tests are indefinitely prolonged in patients. The mode of inheritance is autosomal recessive. Typically patients present with excessive cord bleeding after birth with intracerebral haemorrhages reported in childhood. Other manifestations include musculoskeletal haemorrhages, mucocutaneous bleeds with poor wound healing reported occasionally. In females, menorrhagia, repeated early pregnancy loss and post-partum haemorrhages are common. We present a four year old female who initially presented with severe cord bleeding after birth, warranting a blood transfusion. Currently she experiences recurrent epistaxis, easy bruising and excessive post-traumatic haemorrhages. All her clotting times are markedly prolonged. Her plasma fibrinogen and fibrinogen antigen are undetectable. An older sibling died from excessive cord haemorrhage after birth. Bleeds in CA respond very favourably to fibrinogen concentrates, cryoprecipitate and fresh plasma. To date, 242 cases of CA have been reported worldwide, none of them in Kenya. Our aim in reporting this case is to document the disorder, and also to raise the index of suspicion of the condition.

Disseminated histoplasmosis diagnosed on bone marrow aspirate cytology: report of four cases.

Histoplasmosis, caused by two varieties of dimorphic fungi, Histoplasma capsulatum variant capsulatum and Histoplasma capsulatum variant duboisii is a systemic fungal infection. It has a worldwide distribution and is shown to be more prevalent in North America and Central America. Both variants occur in Africa. Disease spectrum ranges from asymptomatic primary infection to disseminated disease in immunocompromised patients. Since the upsurge of acquired immune deficiency syndrome (AIDS) and despite the availability of high active anti-retroviral therapy (HAART) many patients still present with opportunistic infections of which histoplasmosis is one. Four cases are presented; two infants and two adults. All had disseminated disease with multiple organ involvement and the disease was not suspected clinically. Diagnosis was made incidentally on bone marrow aspirate cytology. The two adult cases were HIV positive, one with CD4 counts of 132 cells/microlitre and was not on HAART. The other was on HAART but the CD4 had not been determined. One of the infants tested HIV negative and the others status was unknown. A high index of suspicion is required for diagnosis as the disease may mimic tuberculosis(TB) and other causes of hepatosplenomegaly such as visceral leishmaniasis. Laboratory diagnosis includes culture, direct staining, antigen and antibody detection. Antibody detection may give false negative in the immunocompromised patient. The infection responds well to antifungal agents (amphotericin B is the drug of choice) and life long maintenance therapy may be required in AIDS especially if CD4 counts remain less than 150 cells/microlitre. Histoplasmosis should be a differential diagnosis in immunosuppressed patients with unexplained fever, weight loss, hepatosplenomegaly and chest findings especially if not responding to anti-TB treatment.

Novel thymidylate synthase enhancer region alleles in African populations.

Thymidylate synthase (TS) regulates the production of DNA synthesis precursors and is an important target of cancer chemotherapy. A polymorphic tandem repeat sequence in the enhancer region of the TS promoter was previously described, where the triple repeat gives higher in vitro gene expression than a double repeat. We recently identified ethnic differences in allele frequencies between Caucasian and Asian populations. We now describe assessment of genotype and allele frequencies of the TS polymorphism in 640 African (African American, Ghanaian and Kenyan) and Caucasian (UK, USA) subjects. The double and triple repeat were the predominant alleles in all populations studied. The frequency of the triple repeat allele was similar between Kenyan (49%), Ghanaian (56%), African American (52%), American Caucasian (54%) and British Caucasian (54%) subjects. However, two novel alleles contained 4 and 9 copies of the tandem repeat. These novel alleles were found at a higher allele frequency in African populations (Kenyan 7%, Ghanaian 3%, African American 2%) than Caucasians (UK 1%, USA 0%). The novel alleles identified in this study decrease in frequency with Western migration, while the common alleles are relatively stable. This is a unique example suggesting the influence of multiple selection pressures within individual populations. Hum Mutat 16:528, 2000.

Ethnic differences in thiopurine methyltransferase pharmacogenetics: evidence for allele specificity in Caucasian and Kenyan individuals.

Thiopurine methyltransferase (TPMT) degrades 6-mercaptopurine, azathioprine and 6-thioguanine which are commonly used in the treatment of autoimmune diseases, leukaemia and organ transplantation. TPMT activity is polymorphic as a result of gene mutations. Heterozygous individuals have an increased risk of haematological toxicity after thiopurine medication, while homozygous mutant individuals suffer life threatening complications. Previous population studies have identified ethnic variations in both phenotype and genotype, but limited information is available within African populations. This study determined the frequency of common TPMT variant alleles in 101 Kenyan individuals and 199 Caucasians. The frequency of mutant alleles was similar between the Caucasian (10.1%) and Kenyan (10.9%) populations. However, all mutant alleles in the Kenyan population were TPMT*3C compared with 4.8% in Caucasians. In contrast TPMT*3A was the most common mutant allele in the Caucasian individuals. This study confirms ethnic differences in the predominant mutant TPMT allele and the findings will be useful for the development of polymerase chain reaction-based strategies to prevent toxicity with thiopurine medications.

Ethnic differences in catechol O-methyltransferase pharmacogenetics: frequency of the codon 108/158 low activity allele is lower in Kenyan than Caucasian or South-west Asian individuals.

Catechol O-methyltransferase (COMT) inactivates neurotransmitters, hormones and drugs such as levodopa. COMT activity is inherited in an autosomal recessive manner and individuals with low activity have thermolabile COMT protein. A low activity allele has been demonstrated at codon 108/158 of the soluble and membrane bound COMT protein, respectively, whereby a G to A transition results in a valine to methionine substitution, rendering the protein more thermolabile. As ethnic differences in erythrocyte COMT activity have been previously demonstrated, the frequency of low activity alleles were investigated in 265 British Caucasian, 99 British South-west Asian and 102 Kenyan individuals. Genotyping of COMT codon 108/158 was performed using a minisequencing method. Erythrocyte COMT activity was measured in 60 British Caucasian individuals by radiochemical assay. The frequency of low activity alleles was 0.54 in Caucasians, 0.49 in South-west Asians, and 0.32 in Kenyans. There was a much lower frequency of individuals with homozygous low activity allele in the Kenyan population (9%) than in Caucasians (31%) or South-west Asians (27%). Erythrocyte COMT activity was lower and less thermostable in individuals with homozygous low activity alleles. The data provide molecular evidence that low COMT is less common in African individuals than the Caucasian population.

MDR1 pharmacogenetics: frequency of the C3435T mutation in exon 26 is significantly influenced by ethnicity.

P-glycoprotein (PGP), the product of the multidrug resistance gene (MDR1), acts as an energy-dependent efflux pump that exports its substrates out of the cell. PGP expression is an important factor regulating absorption of a wide variety of medications. It has also been associated with intrinsic and acquired cross resistance to a number of structurally unrelated anticancer drugs. A single nucleotide polymorphism (SNP) in exon 26 of the MDR1 gene, C3435T, was recently correlated with PGP protein levels and substrate uptake. Individuals homozygous for the T allele have more than four-fold lower PGP expression compared with CC individuals. As overexpression of PGP has been associated with altered drug absorption, therapy-resistant malignancies, and lower concentrations of HIV-1 protease inhibitors, this SNP may provide a useful approach to individualize therapy. To facilitate clinical application throughout the world, 1280 subjects from 10 different ethnic groups were evaluated for this SNP using the polymerase chain reaction-restriction fragment length polymorphism assay and the genotype and allele frequency for each group were ascertained. Marked differences in genotype and allele frequency were apparent between the African populations and the Caucasian/Asian populations (P < 0.0001). The Ghanaian, Kenyan, African American and Sudanese populations studied had frequencies of 83%, 83%, 84% and 73%, respectively, for the C allele. The British Caucasian, Portuguese, South-west Asian, Chinese, Filipino and Saudi populations had lower frequencies of the C allele compared to the African group (48%, 43%, 34%, 53%, 59%, and 55%, respectively). The high frequency of the C allele in the African group implies overexpression of PGP and may have important therapeutic and prognostic implications for use of PGP dependent drugs in individuals of African origin.

Diagnosis of disseminated alveolar rhabdomyosarcoma using cytogenetics: case report.

The clinical, histologic and cytogenetic features of a patient with the alveolar subtype of rhabdomyosarcoma (RMS) were investigated. The patient presented with a widely disseminated tumour including bone marrow involvement, and was a diagnostic dilemma. The presence of translocation (2;13)(q37;q14), which is strongly associated with alveolar RMS helped make the diagnosis. A review of other published cases confirms the strong association of (2;13) with alveolar RMS. The importance of considering RMS as a differential diagnosis in patients presenting with disseminated tumour as the only finding is stressed. This case also shows how cytogenetic investigation of similar patients may provide a diagnosis.

Bone marrow examination at a paediatric hospital in Kenya.

OBJECTIVE: To investigate the main indications for, and common conditions found in bone marrow examinations (BME) of children. METHODS: This was a retrospective study from September 1, 1993 to September 3 1998. All bone marrow aspirate and trephine biopsy results were retrieved. The clinical data provided by clinicians were also noted. RESULTS: A total of 97 BME were recorded from patients aged two months to 13 years. The peak ages for BME were six to eight years (24% of patients). The more frequent indications for BME were unexplained anaemia found in 26% request forms, investigation for solid tumours (10%) and lymphoma (10%) and remission assessment after treatment for leukaemia (26%). The main findings were malignancy (27%) with leukaemia being commonest (ALL) 16% of patients and acute myeloblastic leukaemia (5%). Haematinic deficiency was seen in 12.7% of cases with iron deficiency being the commonest. There were some notable differences and similarities in the study as compared to a similar one performed at a local referral hospital. CONCLUSION: The importance of BME as a crucial investigational tool in the management of patients is underscored. Interpretation is more meaningful when the haematologist has adequate clinical data.

Evaluation of dihydropyrimidine dehydrogenase activity in South-west Asian, Kenyan and Ghanaian populations.

AIMS: Dihydropyrimidine dehydrogenase (DPD) reduces endogenous pyrimidines and therapeutic analogues such as the anticancer agent 5-fluorouracil (5FU). Among Caucasian populations DPD activity is highly variable and subject to polymorphic regulation. To evaluate interethnic influence, DPD activity was assessed in South-west Asian, Kenyan and Ghanaian populations. METHODS: DPD activity was determined in peripheral mononuclear cells using[14C]-5-fluorouracil and h.p.l.c. analysis. RESULTS: A high degree of variation in DPD activity was observed within each population (range CV = 34-48%). Median DPD activity also varied between these populations. South-west Asian and Kenyan subjects exhibited almost identical median values (192 and 193.5 pmol min(-1) mg(-1), respectively), which were similar to Caucasians (median 215 pmol min(-1) mg(-1). A significantly lower median DPD activity (119 pmol min(-1) mg(-1)) was observed in the Ghanaian population. CONCLUSIONS: The similarity in DPD activity between Caucasian, Kenyan and South-west Asian populations suggests that the incidence of 5FU-related toxicity may be comparable in these groups. The pharmacokinetic implications of lower activity amongst Ghanaians needs to be evaluated.