Which of the following is most useful in Rx of Kostmann's Syndrome ?

Kostmann disease was first described in 1956 as an autosomal recessive disorder characterized by severe neutropenia and onset of severe bacterial infections early in life Filgrastim/lenograstim (G-CSF) in Kostman syndrome There is an induction phase with G-CSF to evaluate the response of individuals, with an increase in absolute neutrophil count (ANC) (>1500/mL) and clinical improvement after 10-15 days. The initial daily dose is 5 mg/kg subcutaneously. If there is no response after 15 days, the daily dose is increased by 5 mg/kg. If the response is rapid or excessive (ANC >5000 /mL), the dose is halved. Once the minimal daily dose is determined, the maintenance phase can begin, with monitoring of neutrophil counts every 3-6 months. Almost two thirds of patients respond to a daily dose of 2-10 ug/kg, while 20% respond to 10-20 mg/kg. A small percentage of patients require higher doses, up to 100 mg/kg. Around 10% of patients are unresponsive to G-CSF therapy. Ref - harrison 20th edition 740 , medscape.com