Cyclic neutropenia is another inherited type of neutropenia. As the name indicates, in this disease neutrophil counts show a cyclic pattern with a typical cycle length of 21 days. These cycles vary from patient to patient with some individuals being neutropenic during the whole cycle and others who have low neutrophil counts for only a few days and normal blood counts during the rest of the cycle. The frequency of bacterial infections depends on the length of the neutropenic period that the patient experiences. Those who have a longer neutropenic period within the cycle suffer more frequently from infections compared to patients who have only short neutropenic phases.
If infections (typically aphthous stomatitis - inflammation and ulceration of the mouth) occur frequently in approximately 3-week intervals, cyclic neutropenia should be considered and serial differential blood counts need to be performed (at least 3 times per week over six weeks) to search for the typical cyclical pattern of blood neutrophils in this disease.
Almost all patients with clinically obvious cyclic neutropenia have periods of severe neutropenia (ANC less than 200 cells/Ál) (0.2 x 109/l) every 3 weeks showing some symptoms with almost every cycle, but significant infections (e.g. otitis media, pneumonia and bacteraemia) usually are infrequent. Cyclic neutropenia occurs because of fluctuating rates of cell production by the bone marrow stem cells. In contrast to other causes for neutropenia, in this condition the marrow changes during the cycle, between normal appearance and that of severe maturation arrest of neutrophil production. The underlying genetic defect of cyclic neutropenia has recently been discovered. This might lead to new therapeutical approaches for cyclic neutropenia patients in the future.
Other blood cells, such as platelets or red cells can also show oscillations with a cyclical pattern. Cyclic neutropenia can occur sporadically, but there are families in which cyclic neutropenia is inherited with one parent and more than one child affected. As in Kostmann syndrome, patients with cyclic neutropenia also benefit from G-CSF treatment.