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Signs and symptoms
The clinical hallmark is haemorrhagic bullae on the mucosa of the oronasopharynx. Haemorrhage from ruptured bullae, epistaxis or gastrointestinal bleeding is severe and may cause shock and death.
Onyalai is an acute disease that results in the development of hemorrhagic lesions on oral, nasal, and subconjunctival mucous membranes and skin, including on the soles of the feet. The patient initially is not in distress, which may result in a delay of diagnosis. As the disease progresses, hematuria, melena and menorrhagia may develop. Bleeding usually persists for approximately eight days, and may recur. Approximately 80 percent of cases will develop chronic thrombocytopenia. Periodic episodes of acute hemorrhage are possible and may be severe, leading to shock and death.
Inadequate nutrition or the consumption of tainted food are suspected. Both IgG and IgM autoantibodies to platelet and to glycoprotein IIb/IIIa is found in majority of patients.
Treatment is directed at the prevention of haemorrhagic shock. Standard dose prednisolone does not increase the platelet count. High-dose methylprednisolone therapy in children with Onyalai has been shown to improve platelet count and reduce the requirement for transfusions. Vincristine sulphate may be of benefit to some patients. Splenectomy is indicated in patients with severe uncontrollable haemorrhage. High-dose intravenous gammaglobulin may help in increasing the platelet count and cessation of haemorrhage.
Onyalai is limited to black populations in central southern Africa. The affected age range is from less than a year to 70 years and seems not to be gender-specific in the same manner as ITP. Cases generally peak between 11 and 20 years old.
Analysis of patient admissions in Namibia between 1981 and 1988 showed an incidence rate of onyalai to be 1.19% with the annual incidence varying between 0.96% and 1.66% of all admissions. The female to male ratio was 3:2. The mean age at presentation was 24.8 years (range 6 months to 80 years) and the mean hospital stay (and duration of clinical bleeding) was 7.68 days (ranging between 1–38 days). The treatment policy of commencing intravenous fluid on admission and a blood transfusion whenever the haemoglobin dropped below 10 g/dl in patients with active bleeding was associated with a mortality rate of 2.78% compared to 9.8% in cases recorded up to 1981.
The first case was reported in 1904 by Wellman.
- Hesseling, PB (Apr 1992). "Onyalai". Baillière's Clinical Haematology. 5 (2): 457–73. PMID 1511183. doi:10.1016/s0950-3536(11)80027-2.
- "Onyalai".[dead link]
- Hesseling, PB; Smith, S; Oosthuizen, O; Amadhila, S (1994). "High dose methylprednisolone therapy in children with onyalai.". Annals of Tropical Paediatrics. 14 (3): 239–43. PMID 7825998.
- Hesseling, PB; Girdle-Brown, B; Smit, J (Aug 16, 1986). "Onyalai--therapeutic effects of vincristine sulphate. A prospective randomized trial.". South African medical journal. 70 (4): 201–2. PMID 3738655.
- Hesseling, PB; Oosthuysen, E; Pretorius, L; Swart, A; Steynberg, J (Oct 13, 1984). "Splenectomy in onyalai. A report on 5 cases.". South African medical journal. 66 (15): 580–2. PMID 6495094.
- Hesseling, PB (Jul–Aug 1990). "Onyalai at Rundu, Namibia 1981-1988: age, sex, morbidity, mortality and seasonal variation of 612 hospitalized patients.". Transactions of the Royal Society of Tropical Medicine and Hygiene. 84 (4): 605–7. PMID 2091364. doi:10.1016/0035-9203(90)90057-l.