This study tests a medicine called mavorixafor for people who have problems with their immune system, making them get sick often. It focuses on those with congenital (from birth) or acquired (developed later) issues causing low levels of neutrophils, a type of white blood cell important for fighting infections. Participants will keep taking their usual treatments, like granulocyte-colony stimulating factor (G-CSF), which helps boost white blood cells, or antibiotics.

Key points to consider:

• The study involves taking mavorixafor while continuing current treatments.
• Participants must have a history of recurrent or serious infections.
• Some people with secondary causes of low neutrophils or certain other conditions cannot participate.

Doctors will measure how well mavorixafor works by checking if it raises neutrophil levels and reduces infections. The goal is to see if it's safe and helpful for those with these immune problems. Participants must be committed to maintaining their current treatment plans and attend scheduled medical visits. Always talk with your healthcare provider to see if joining is a good choice for you.