Does Cutaneous Mastocytosis Run in Families?
Cutaneous mastocytosis is overwhelmingly sporadic and does not typically run in families—familial cases are rare, accounting for a small minority of cases. 1
Evidence for Sporadic Nature
The most authoritative guideline data from the American Journal of Clinical Dermatology explicitly states that familial cases are rare in pediatric cutaneous mastocytosis. 1 This represents the consensus view based on large case series and clinical experience.
Documented Familial Cases
While rare, familial inheritance has been documented:
In a retrospective Israeli study of 180 pediatric patients with mastocytosis, only 13 out of 117 cases (11%) of urticaria pigmentosa were familial, affecting 5 families total. 1
Critically, only one generation was affected in these familial cases, suggesting limited vertical transmission. 1
No familial history was found in mastocytomas (the solitary nodular form). 1
Identical twins and triplets have been described, though these remain exceptional case reports. 1
One family with telangiectasia macularis eruptiva perstans (TMEP, a rare adult variant) affecting three generations has been reported, supporting possible autosomal dominant inheritance with incomplete penetrance in that specific subtype. 2
Genetic Considerations
The pathogenesis differs between pediatric and adult forms:
Many children with cutaneous mastocytosis do not present c-kit mutations, which are commonly found in adult systemic mastocytosis. 1
When present in children, c-kit mutations are typically sporadic somatic mutations at codons 816,820, or 839, not inherited germline mutations. 1
Recent literature notes that both sporadic and hereditary factors may be involved in rare severe forms like diffuse cutaneous mastocytosis, though specific gene mutations in familial cases remain under investigation. 3
Clinical Implications
You should counsel families that:
The vast majority of cutaneous mastocytosis cases occur sporadically without family history. 1
The risk of recurrence in siblings or offspring is extremely low based on available data. 1
Males and females are equally affected, with no racial predominance. 1
The excellent prognosis in pediatric cutaneous mastocytosis (60-80% resolve spontaneously by puberty) applies regardless of familial or sporadic occurrence. 1
Common Pitfall
Do not confuse the presence of c-kit mutations with familial inheritance—these are typically acquired somatic mutations in mast cells, not inherited germline mutations passed from parents to children. 1