Favorable course of previously undiagnosed Methylmalonic Aciduria with Homocystinuria (cblC type) presenting with pulmonary hypertension and aHUS in a young child: a case report

Background: Cobaiamin C (cblC) defect is the most common inborn erroi of Vitamin B12 metabolism often causing severe neurological, renal, gastrointestinal and hematological symptoms. Onset with pulmonaiy hypertension (PAH) and atypical hemolytic uremic syndrome (aHUS) is rare. Case presentation: We descnbe the case of a 2-years old child, previously in good health, admitted to the hospital with severe respiratory symptoms, rapid worsening of clinical conditions, 0? desaturation and palmo plantar edema. The patient showed PAH and laboratory findings compatible with aHUS. cblC defect, an inborn error of metabolism, was identified as the cause of all the symptoms described (cardiac, respiratory and lenal involvement). Results of neonatal screening for inborn eirors of metabolism had been negative. Administration of IM OHCbl (intramuscular hydroxocobalamin), oral betaine and symptomatic treatment with diuietics and anti hypertensive systemic and pulmonary drugs induced dramatic improvement of both cardiac and systemic symptoms Conclusions: In this case of cbIC defect the metabolic treatment completely reverted symptoms of aHUS and PAH. The course was favorable, and the prognosis is what we foresee for the future.