I checked the dev log after loading a save and this error was present. It appears the hediff for neoderm is being removed at start.

Exception ticking hediff (FF_NeodermHigh ticksSinceCreation=14405) for pawn Mattsson. Removing hediff... Exception: System.MissingMethodException: void Verse.HealthUtility.CureHediff(Verse.Hediff)
at (wrapper dynamic-method) FF_Drugs.HediffComp_SelectiveRegeneration.FF_Drugs.HediffComp_SelectiveRegeneration.CompPostTick_Patch0(FF_Drugs.HediffComp_SelectiveRegeneration,single&)
at Verse.HediffWithComps.PostTick () [0x00024] in <1b9c4c73530448bcbb33283e1d4d7d05>:0
at (wrapper dynamic-method) Verse.Pawn_HealthTracker.Verse.Pawn_HealthTracker.HealthTick_Patch1(Verse.Pawn_HealthTracker)
UnityEngine.StackTraceUtility:ExtractStackTrace ()
(wrapper dynamic-method) Verse.Log:Verse.Log.Error_Patch2 (string)
(wrapper dynamic-method) Verse.Pawn_HealthTracker:Verse.Pawn_HealthTracker.HealthTick_Patch1 (Verse.Pawn_HealthTracker)
(wrapper dynamic-method) Verse.Pawn:Verse.Pawn.Tick_Patch3 (Verse.Pawn)
Verse.TickList:Tick ()
(wrapper dynamic-method) Verse.TickManager:Verse.TickManager.DoSingleTick_Patch3 (Verse.TickManager)
Verse.Game/<>c:<LoadGame>b__60_1 ()
Verse.LongEventHandler:ExecuteToExecuteWhenFinished ()
Verse.LongEventHandler:UpdateCurrentAsynchronousEvent ()
Verse.LongEventHandler:LongEventsUpdate (bool&)
(wrapper dynamic-method) Verse.Root:Verse.Root.Update_Patch1 (Verse.Root)
Verse.Root_Play:Update ()